GERO Final
Henrietta Lacks
- Obtained (without permission) from cervical cancer biopsy - Henrietta's cells were the first immortal human cells ever grown in culture. - They were essential to developing the polio vaccine. - They went up in the first space missions to see what would happen to cells in zero gravity. - Many scientific landmarks since then have used her cells, including cloning, gene mapping and in vitro fertilization. - More than 60,000 scientific articles had been published about research done on HeLa, and that number was increasing steadily at a rate of more than 300 papers each month - Lacks' family found out 25 years after her death that the cells were being used.
Hutchinson-Gilford progeria syndrome
- Single point mutation in the Lamin A gene, a structural component of the human cell nucleus - Hair loss, stiff joints, wrinkled skin, loss of eye sight, cardiovascular problems at childhood
Werner syndrome
-Single point mutation in the WRN gene, a component of the DNA surveillance system - By age 30-40 look decades older. Early thickening of skin, graying of hair, diabetes, cataracts, atherosclerosis, cancer unlike the previous two disorders, will often go unnoticed until the child reaches puberty and fails to go through a normal growth spurt. The symptoms of premature aging set in after the age of 10. Each disorder produces the effects of premature aging, but the means by which they affect the chromosomes and the body are very different.
Process of Cancer
1. DNA mutation: This DNA has suffered a mutation, either through mis-copying (when its parent cell divided), or through the damaging effects of exposure to radiation or a chemical carcinogen. 2. Genetically altered cell Body cells replicate through mitosis, they respond to their surrounding cells and replicate only to replace other cells. Sometimes a genetic mutation will cause a cell and its descendants to reproduce even though replacement cells are not needed. The DNA of the cell highlighted above has a mutation that causes the cell to replicate even though this tissue doesn't need replacement cells at this time or at this place. 3. Spread and second mutation The genetically altered cells have, over time, reproduced unchecked, crowding out the surrounding normal cells. The growth may contain one million cells and be the size of a pinhead. At this point the cells continue to look the same as the surrounding healthy cells. After about a million divisions, there's a good chance that one of the new cells will have mutated further. This cell, now carrying two mutant genes, could have an altered appearance and be even more prone to reproduce unchecked. 4. 3rd Mutation Not all mutations that lead to cancerous cells result in the cells reproducing at a faster, more uncontrolled rate. For example, a mutation may simply cause a cell to keep from self-destructing. All normal cells have surveillance mechanisms that look for damage or for problems with their own control systems. If such problems are found, the cell destroys itself. Over time and after many cell divisions, a third mutation may arise. If the mutation gives the cell some further advantage, that cell will grow more vigorously than its predecessors and thus speed up the growth of the tumor. 5. 4th mutation • The new type of cells grow rapidly, allowing for more opportunities for mutations. The next mutation paves the way for the development of an even more aggressive cancer. At this point the tumor is still contained. 6. Breaking through the membrane • The newer, wilder cells created by another mutation are able to push their way through the epithelial tissue's basement membrane, which is a meshwork of protein that normally creates a barrier. The invasive cells in this tumor are no longer contained. At this point the cancer is still too small to be detected. 7. Angiogenesis Often during the development of earlier stages of the tumor, or perhaps by the time the tumor has broken through the basement membrane (as pictured above), angiogenesis takes place. Angiogenesis is the recruitment of blood vessels from the network of neighbouring vessels. Without blood and the nutrients it carries, a tumor would be unable to continue growing. With the new blood supply, however, the growth of the tumor accelerates; it soon contains thousand million cells and, now the size of a small grape, is large enough to be detected as a lump 8. Invasion and dispersal • The tumor has now invaded the tissue beyond the basement membrane. Individual cells from the tumor enter into the network of newly formed blood vessels, using these vessels as highways by which they can move to other parts of the body. A tumor as small as a gram can send out a million tumor cells into blood vessels a day. 9. Tumor cells travel and metastasis What makes most tumors so lethal is their ability to metastasize -- that is, establish new tumor sites at other locations throughout the body. Secondary tumors. Metastasis is now underway, as tumor cells from the original cancer growth travel throughout the body. Most of these cells will die soon after entering the blood or lymph circulation. 10. Metastasis • To form a secondary tumor, a tumor cell needs to leave the vessel system and invade tissue. The cell must attach itself to a vessel's wall. Once this is done, it can work its way through the vessel and enter the tissue. Although perhaps less than one in 10,000 tumor cells will survive long enough to establish a new tumor site, a few survivors can escape and initiate new colonies of the cancer.
How do we identify aging genes?
1. Mutate one gene at a time→ what changed→ does it change function 2. Identify mutant→ what changed→ identify gene responsible
Evidence based common denominators to living longer
1. Purpose 2. Down shift 3. 80% rule 4. plant shift 5. wine at 5 6. right tribe 7. loved ones first 8. belong 9. move naturally
APOE4 carriers
APOE4 carriers with greater amyloid pathology had a lower increase in total CSF DHA and EPA after supplementation • (1) APOE4 carriers may require longer duration of high dose DHA supplementation • (2)Reduced DHA brain delivery precedes cognitive impairment in APOE4 carriers and associates with greater amyloid deposition
What happened to the telomerase gene after fetal development?
After fetal development, telomerase gene is turned off Via DNA methylation and histone modification at promoter or regulator region (positively charged histone, so acetylation), specifically deacetylation I.e. methylation at promoter region of telomerase
Chronological age
Age as measured in years from date of birth
Biological age
Aging occurs with gradual damage to cells/tissues in the body Alteration in structure/function due to genetic and environmental and random factors (rate therefore varies) Also random change due to environmental interaction Accumulation of damage
Apoptosis
Apoptosis is a normal part of development and tissue maintenance. An estimated 50% of all cells formed during fetal tissue and organ development are removed by apoptosis. Aging-associated disruptions result in increased apoptosis. Extrinsic and intrinsic apoptosis Mutations that make apoptosis slower→ slow down removal of cells→ lead to cancer/mutations
Why do we have a higher risk of cancer as we get older?
As we get older, weaker immune system→ less killer T cells More mutation due to environmental factors/errors in replication machinery
HGPS syndrome
Atherosclerosis: which is the thickening and hardening of the arterial walls. It restricts blood flow that carries important nutrients and oxygen to the entire body. Heart Attacks: when a part of the heart is cut off from the blood supply, so therefore does not receive any oxygen. Often occurs from a blood clot because the child has atherosclerosis, which narrows the pathways for blood to travel through. Arthritis: inflammation of the joints. It generally is very painful and causes them to be become stiff. Osteoporosis: the thinning of the bone tissue and loss of bone density. *This is why children with progeria can be three feet tall but only weigh about 24 pounds. Insulin Resistance: when the body produces insulin but does not use it properly. Stroke: when a part of the brain is cut off from the blood supply, therefore cutting off the oxygen supply to the brain causing the brain tissue to die. Cataracts: when clouding develops inside the lens of the eye. Tumors: the abnormal growth of body tissue.
BRCA2
BRCA2 (Breast Cancer 2 susceptibility protein) is a protein that in humans is encoded by the BRCA2 gene. BRCA2 orthologs have been identified in most mammals for which complete genome data are available. BRCA2 belongs to the tumor suppressor gene family and the protein encoded by this gene is involved in the repair of chromosomal damage with an important role in the error-free repair of DNA double strand breaks.
Benign tumors
Benign tumors do not spread from their site of origin, but can crowd out (squash) surrounding cells (eg brain tumor, warts, benign polyps).
Loosely coupled vs tightly coupled mitochondria
Brown fat generates heat: not sufficient to adapt in long term cold environment→ mitochondrial mutation to adapt to cold weather, prone to produce less ATP and generate more heat Decreased membrane potential (need more H+ to generate ATP)--> increased oxidation of electron transport chain (inefficient ATP production)--> keep transfer electrons (not enough electrons to donate to oxygen) Loosely coupled mitochondria Tropic: a lot of electrons in chain can donate to O2 Tightly coupled mitochondria It is also suggested that that the selection of mtDNA variants which allowed energy production even in time of food shortage (tight coupling to maximum ATP production) may now expose us in the presence of excess calories in food to excess ROS (reactive oxygen species). This in turn may cause mtDNA damage and mitochondrial decline that contributes to metabolic and degenerative diseases, ageing and cancer (Wallace 2005)
What happens when we remove senescent cells?
CAP 8 to induce apoptosis under p16 promoter→ any senescent cells will be killed To activate caspase 8 they need to inject a chemical to induce Inject with AP and kill most of senescent cells → increase lifespan by 25%
ROS benefits
Can act as a signaling molecule Useful in immune function for destroying foreign cell invaders Short-term oxidative stress may also be important in prevention of aging by induction of a process named mitohormesis.
What causes cancer?
Cancer arises from the mutation of a normal gene. Mutated genes that cause cancer are called oncogenes. Tumor-suppressor genes normally code for proteins that inhibit cell division. A mutation that deactivates a tumor- suppressor gene result in cancer. It is thought that several mutations need to occur to give rise to cancer Cells that are old or not functioning properly normally self destruct and are replaced by new cells. However, cancerous cells do not self destruct and continue to divide rapidly producing millions of new cancerous cells.
Sarcoma
Cancers arising from connective tissue (i.e. bone, cartilage, fat, nerve), each of which develop from cells originating in mesenchymal cells outside the bone marrow.
Carcinoma
Cancers derived from epithelial cells. This group includes many of the most common cancers, particularly in the aged, and include nearly all those developing in the breast, prostate, lung, pancreas, and colon.
Blastoma
Cancers derived from immature "precursor" cells or embryonic tissue. These are also most common in children
Germ cell tumor
Cancers derived from pluripotent cells, most often presenting in the testicle or the ovary (seminoma and dysgerminoma, respectively).
Malignant tumors
Malignant tumors can spread from the original site and cause secondary tumors. This is called metastasis. They interfere with neighbouring cells and can block blood vessels, the gut, glands, lungs etc. Both types of tumor can tire the body out as they both need a huge amount of nutrients to sustain the rapid growth and division of the cells.
Hutchinson-Gilford Progeria Syndrome
causes premature aging in children usually within the preschool years of life.
cellular senescence
stable arrest of the cell cycle coupled to secretory phenotypic changes Senescence are more larger/flat Overexpression of b galactosidase in lysosome Not dividing but highly active (higher gene expression, i.e. more pro-inflammotry)
stress-induced premature senescence
suppress tumor genesis in response to ROS, DNA damage, stress
replicative senescence
the loss of the ability of cells to reproduce i.e. due to telomere shortening ageing
Intrinsic apoptosis
trigger by stimuli from within cell mitochondria release cytochrome c cytochrome c binds Apaf1 and Casp 9 Casp 9 activate each other Casp 9 activate Casp3 triggered by the inside→ BcI2 anti-apoptotic proteins Caspase→ induce apoptosis (degrade cellular component and cause cell to shrink)
HeLa cells
Cells removed from cancer cells→ have infection Telomerase expressed→ immortal - Contain active version of telomerase during cell division, which prevents the incremental shortening of telomeres that is implicated in aging and eventual cell death. In this way, HeLa cells circumvent the Hayflick Limit, which is the limited number of cell divisions that most normal cells can later undergo before becoming senescent. - HeLa cells have a modal chromosome number of 82, with four copies of chromosome 12 and three copies of chromosomes 6, 8, and 17. - Due to their ability to replicate indefinitely, and their non-human number of chromosomes, HeLa was described by Leigh Van Valen as an example of the contemporary creation of a new species, Helacyton gartleri. - It has been estimated that the total number of HeLa cells that have been propagated in cell culture far exceeds the total number of cells that were in Henrietta Lacks's body.
Senescense
Cellular - The phenomenon that "normal" cells lose the ability to divide Sometimes in younger individuals natural killer cells/macrophages remove senescence cells and remove cytokines that can damage tissue Elderly: cytokines is released which can damage cells → lead to tissue/organ dysfunction (leads to aging) but is protection against cancer •Organism - for all intent this is "aging". Failure of the body to respond to stress and adapt. - Senescence of the organism gives rise to the Gompertz-Makeham law of mortality, which says that mortality rate rises rapidly with age.
Social aging
Change in person's role and relations relate to friends/family/workplaces Disengagement theory: Old age: become emotionally distanced Typical engagement tho found didn't change Social well-being: retirement has huge impact psychological aging Social aging after retirement varies bigger Some people find new hobbies/interests but other have a difficult time to develop new routines and develop chronic diseases Social aging reinforced by perspective in their own society I.e. negative perspective in US is not positive so leads to elderly abuse/neglect
APOE4
Common genetic polymorphism Strongest genetic risk factor for AD The risk differs by ethnicity ApoE4 modifies how cells utilize glucose, fatty acids, and their response to stress/inflammation As aggregate→ inflammation and oxidative stress Affect transport of glucose/fatty acids ApoE4 alters the integrity of the blood-brain barrier and affects nutrient brain delivery As we age less glucose is getting into our brain APOE4 carriers have less omega 3 after supplementation Brain nutrient transport in AD Focus on omega 3 because it shown to be neuroprotective Aging rate switches from glucose to fat Glucose is less efficient to getting into the brain ApoE4 in AD induces MAPK P38 activation predisposes the brain to neuroinflammation
Can inject neoblast lead to a regeneration of a whole organism?
Cut planaria in half→ each half will grow into their own organism Due to neoblasts: dividing cells that is non-differentiated (like stem cells) Can inject neoblast lead to a regeneration of a whole organism? Neoblast: 30% of all cells in planaria and only dividing cells Expose to radiation: rapid dividing cells (neoblast) destroyed Inject 1 neoblast into animals Was able to regenerate all of the tissue in the planaria Used asexual strand of planaria to distinguish donor from host Asexual planaria lives up to 20 days Regenerate worm and cut diff parts to do phenotyping 1 from the host, the other 3 are the same as the asexual planaria
mtDNA contribution to the reconstruction of human history
Depends on:- •High mutation rate (especially in D loop region) •Maternal transmission •No recombination This allows the origins of female ancestors to be deduced Some of the mtDNA variants are found more frequently in humans in cold climates such as Siberia and they are thought to alter the balance of production of energy (ATP) versus Heat per calorie consumed.
Cancer
Divide out of control and can crowd out normal function (destroy normal function) The division of normal cells is precisely controlled. New cells are only formed for growth or to replace dead ones. Cancerous cells divide repeatedly out of control even though they are not needed, they crowd out other normal cells and function abnormally. They can also destroy the correct functioning of major organs.
Hormetic response
Exposing cell/organism to mild stress allows for an adaptive response (hormetic) that yields biological benefits.
How would you design an experiment to determine the decline of lysosome and UPS function when aging?
Lower genes in pathway (i.e. p62) or functional decline of pathway→ correlate with decline in C. elegans (is it because the worm is old or the machinery is dysfunctional) Test with young C. elegans→ RNAi (silencing RNA) or inhibit p62 or autophagy pathway→ whether autophagy will shorten lifespan → shorten lifespan (b/c autophagy pathway clear out age-related accumulations)
Calorie Restriction
Extends the lifspan of: yeast, flies, worms, mice, rats, and probably monkeys. Lowers the incidence of age-related diseases. Seems to have a neuroprotective component. BUTDoesn't help the change in sleep patterns that occurs in older animals.Some animals and strains of animals have been shown not to be affected by CR. the point of life is to reproduce, under conditions where that is not possible, it is best to try to maintain the organism until it can reproduce. Starvation without malnutrition (often times they add additional vitamins) 30% Decreases in food intake -> ~30% increase in lifespan Works in yeast, flies, worms, mice, dogs, and maybe in primates More susceptible to hypothermia May decrease immune response Stress Resistance is often observed in organisms under DR. Reproductive age extension is often observed in organisms under DR.
Life of the mitochondrion
Fission: increase in mitochondrial number --> fissioned mitochondria--> out of cycle to form mitophagy (degradation) Fission: take out part of mitochondria that has damage (split into more mitochondria and is removed) through mitophagy biogenesis (synthesis) can come in to form fusion (increase in mitochondrial mass) --> fused mitochondria mitochondria synthesis occurs from nucleus and mitochondria protein synthesis
What if we remove senescent cells?
High p16→ induce senescence Caspase: activate cell death Cells express p16→ increase caspase promoter Inject chemical will activate caspase Remove age related disorders
Does telomere length (telomerase activity) predict lifespan?
If tissue have higher telomerase activity among different rodent species → amplify telomerase substrate→ die with cancer Positive control (expect 100% you have polymerase activity): human cancer cell line Test different organ tissues Results: telomerase activity does not predict maximum lifespan Negative correlation between body mass and telomerase activity But relationship between rate of telomere shortening and maximum lifespan • Telomeres and telomerase are important for cancer biology• Telomere shortening and the cellular stress response activated from this process may influence age-related diseases (like cancer)• A direct link of telomerase and telomere length to aging is not clear...yet
Immune system
Innate Immunity: Comprised of hereditary (always there) components that provide an immediate "first-line" of defense to continuously ward off pathogens. Adaptive (acquired) Immunity: By manufacturing antibodies (a type of protein) and T-cells specifically designed to target particular pathogens, the body can develop a specific immunity to particular pathogens. This response takes days to develop, and so is not effective at preventing an initial invasion, but it will normally prevent any subsequent infection, and also aids in clearing up longer-lasting infections.
Telomeres and Aging
It has been proposed that telomere shortening may be a molecular clock mechanism that counts the number of times a cell has divided and when telomeres are short, cellular senescence (growth arrest) occurs. Once the telomere shrinks to a certain level, the cell can no longer divide. Its metabolism slows down, it ages, and dies.
HGPS prelamin A processing
LMNA protein undergo farneslation (methylation) Add farnesyl group to C and cleavage off of last 3 amino acid Translated into prelamin A and mature lamin A In truncated form of Lamin A Abnormal splicing at mutation splice site Same last 4 amino acid with farnesylation and cleavage Shorter mutant farnesylated prelamin A Lamin protein normally stay near nucleoplasm Mutated bind to nuclear membrane and bind heterochromatin, disrupt heterochromatin organization proffering anchored to the nuclear rim--> abnormally shaped nucleus Transcriptional repression Of histone (methylation) in HGPS fibroblasts Bridge between chromatin In daughter cells (normal cells have clear separation)
Effects of having longer telomeres
Longer telomere length predispose to cancer TIN2: play a role in telomere formation→ mutation in gene leads to longer telomere length in the family Have longer telomere= have senescence after more doubling time→ more chance to accumulate mutation and predispose to cancer
Psychological aging
Mental function and personality Old study: Confusion due to cognitive decline or disease (universal decline) Leads to ageism However, longitudinal study shows trace outcomes across lifespan Found four categories: Successful/healthy aging (normal function until they die, show very minor decline, small decrease before dying) General/Average aging (most common, modest decline until die) Mild cognitive impairment: Greater than normal cognitive decline in old age (clinical dementia score) Dementia: characterized by dementia in early or middle age
Tay-Sachs Disease
Metabolic disorders effecting 1 in 10,000 people Missing enzyme required for lipid or sugar metabolism. (lipid storage disorders) Age related symptoms include, seizures (neuro), ataxia (movement), dementia, blindness, deafness, organ failure.
Proteasome
Misfolded protein due to mutation If chaperone cannot fix the probem→ 3 enzyme add ubiquitin to misfolded protein (ubiquitin chain) Recognized and threaded through UPS During aging in multiple organisms, proteins involved in UPS activity decline, proteasome subunit are not arranged well (disassembled)--> deactivated proteasome (in aging tissue and senescence cell) Lysosome function also decline (pH in lysosome declines and digestive enzyme activity decline)--> autophagy activity declines
Pathway of carcinogenesis
Mutation of tumor suppressor(APC) Normal cell→ early adenoma Mutation of proto-oncogene (2) Late adenoma 2 mutations in tumor supressors Carcinoma Protooncogene mutation is like an accelerator for cancer suppression Oncogene mutation is a result of turn on the function Tumor suppressor gene mutation: caused when mutation inactivates tumor suppressors
Is aging a disease?
No Disease: a disordered/impaired normal function Aging occurs in all animals in animate/inanimate objects Cannot be modulated Anti-aging supplement Most are not approved by FDA and not sure if it is really effective
Therapeutic cloning of stem cells
Nuclear transfer method: Take cell and remove nucleus Take egg cell and remove nucleus Inject nucleus from skin cell and inject into egg → embryo→ stem cells
what happens if we give omega-3 supplementation to elderly?
Older APOE4 carriers with mild AD do not respond to omega-3 supplementation Older APOE4 carriers with mild AD or greater amyloid pathology have lower brain transport of glucose and omega-3s.
Economic aging
Older population shift→ lose capability to work in society= think about relocation of services from childcare services to pensions/senior housing/nursing homes People who can contribute from pension/beneficiary is increasing when retiring Impact on social welfare/supplies/demand
Oxygen radicals and complex IV
Oxygen radicals can cause peroxidation of nearby lipids These Lipid peroxidation products can then adduct to proteins, ie Complex IV Studies have shown that as adduction of 4-HNE (a lipid peroxidation product) increases, Complex IV activity decreases
What are environmental contributors of cancer during aging?
Pollution, ionizing radiation, red meat Meat (fat) increase prostaglandin synthesis→ can lead to cancer Tar from smoking
Hallmarks of aging
Primary hallmarks: causes of damage Antagonistic hallmarks: responses to damage Integrative hallmarks Culprits of the phenotype
KEAP1-Nrf2 signaling
Proteasome for degradation increased levels of ROS--> change KEAP1--> translocated to nucleus to turn on genes with antioxidant abilities
Can senescence directly drive age-relate pathology?
Put senescence cells in younger animals Most significant effects in 1 million senscence cells induce age-related pathology Observed physical dysfunction Reduction of survival after transplantation of cells (dramatic effect)
Telomeres
Telomerase enzyme adds TTGGGG repeats to end of lagging strand template. Forms hairpin turn primer with free 3'-OH end on lagging strand that polymerase can extend from; it is later removed. Age-dependent decline in telomere length in somatic cells, not in stem cells, cancer cells. Chromosomes you can see during mitosis Ends of chromosomes End replication problem Lose 3' end of lagging strand on linear chromosomes Cell think that this is damage if left hanging→ loop 3' end to form a T and D loop→ ligate to another telomere end Telomerase adds repeats to end of lagging strand template • Repetitive DNA sequences at the ends of all human chromosomes • They contain thousands of repeats of the six-nucleotide sequence, TTAGGG• In humans there are 46 chromosomes and thus 92 telomeres (one at each end)
Telomerase
Telomerase is a ribonucleoprotein enzyme complex (a cellular reverse transcriptase) that has been referred to as a cellular immortalizing enzyme. It stabilizes telomere length by adding hexameric (TTAGGG) repeats onto the telomeric ends of the chromosomes, thus compensating for the erosion of telomeres that occurs in its absence. Most normal cells do not have this enzyme and thus they lose telomeres with each division. Only expressed in stem cells, germ cells, cancer cells Eventually somatic cells shorten telomere→ senescence If not ends will be "repaired"--> lose some functional genes
Reactivation of telomerase experiment
Reactivating telomerase Telomerase enzyme fused with estrogen→ join with estrogen promoter Add OHT when they want to activate telomerase Premature aging was seen Then tried activating for 4 weeks and turning off Cellular level: take out fibroblast and see that telomerase was reactivated, telomeres lengthened and proliferation occurs tissue/Organ: reverse brain size and function to normal (neurogenesis) Organism: reverse life span→ maximum lifespan reached The first test to investigate the effects of telomerase reactivation by means of 4-OHT was done in vitro. Fibroblast cells from TERT-ER mice were cultured under normal conditions and found to be essentially senescent and not undergoing cell cycles. But when the cells were placed in media containing 4-OHT, telomerase was reactivated, telomeres lengthened, and cell proliferation resumed. The first step was to show that without 4-OHT the TERT- ER mice (after a few generations) had many of the same problems, in the same degree, as later generations of knock-out mice that lacked Tert entirely. The TERT-ER mice (all of which were male) without activation, showed no signs of telomerase activity. Tissues in highly proliferative organs such as testes, spleen, and intestines showed notable atrophy. Lifespan of TERT-ER mice was about half that of normal ("wild type") mice. Mice overexpressing telomerase have higher cancer rate and shorter lifespan (Artandi 2002) Mice completely lacking telomerase are viable (6th gen) In this special mouse they replace the TERT KO with an inducible version.
Blue zone
Regions of the world where, it is claimed, a higher than usual number people with the highest life expectancy, or with the highest proportions of people who reach age 100. show how environment/community affects longetivity
How does Telomerase work?
Research also shows that the counter that controls the wasting away of the telomere can be "turned on" and "turned off". The control button appears to be an enzyme called telomerase which can rejuvenate the telomere and allow the cell to divide endlessly. Most cells of the body contain telomerase but it is in the "off" position so that the cell is mortal and eventually dies. Some cells are immortal because their telomerase is switched on High telomerase activity exists in germ cells, stem cells, epidermal skin cells, follicular hair cells, and cancer cells. In humans, telomerase is expressed in germ cells, in vitro immortalized cells, the vast majority of cancer cells and, possibly, in some stem cells. Cancer cells do not age because they produce telomerase, which keeps the telomere intact.
Where do senescent cells accumulate?
Senescent cells accumulate in human adipose tissue with aging Use senescent biomarker to find DNA damage signaling between young and old Cell with damage have no replication Senescence associated with secretory phenotypes Expose human adipocytes with irradiations→ secretory phenotypes are cell type and senecent type specific.
Stem cells
Stem cell: can differentiate into any other cell & are immortal Totipotent (itself), pluripotent (many different types), multipotent (different type of 1 cell type but only 1 cell type) In pluripotent/multipotent have a lot of DNA methylation
Do stem cells age?
Stem cells also "age" HSCs transferred to young hosts retain their aged phenotypes that match the donor. Aged satellite cells display a skewed differential potential (fibrogenic > myogenic) Although most neurons are post-mitotic, NSC sustain neurogenesis in adulthood. NSC numbers decrease with age. Hair folicle stem cells go through stages of (growth, regrowth, rest). With increased age there is an increase rest period, consistent with age-related hair loss.
Nuclear reprogramming of stem cells
Studied what genes make stem cells stem cells and not somatic cells Gene inserted into differentiated cell→ goes back to stem cells
TOR
TOR - Target of Rapamycin Rapamycin - Immunosuppresent drug Discovered in a screen looking for muations that led to rapamycin resistance Highly conserved protein that exists in yeast, flies, worms, mice and humans Nutrient Sensor Senses Amino Acids Sensitive to ATP concentrations Cross-talks with insulin signaling Controls translation via S6K
Telomerase and ALT
Telomerase and ALT 10% of tumor have alternative ways of elongating telomeres other than telomerase activation VS ALT= DNA recombination can lengthen telomerase→ become immortal and cancerous
Young vs old mitochondria
Young mitochondria Lots of energy production Maintain membrane potential Resistant to cell death Intact mtDNA TCA metabolites production Tightly regulated Ca2+ Mitochondrial-derived peptides production increases Old mitochondria • Less energy production • Loss of membrane potential • Prone to cell death • Increased mtDNA mutation • TCA metabolites decline • Excess of Ca2+ • Mitochondrial-derived peptides production decrease
Hayflick limit
The Hayflick limit (or Hayflick Phenomenon) is the number of times a normal cell population will divide before it stops, presumably because the telomeres reach a critical length He showed that nutrition has an effect on cells, with overfed cells dividing much faster than underfed cells. As cells divide to help repair and regenerate themselves we may consider that the DNA damage & Genetic Theory of Aging may play a role here. Maybe each time a cell divides it loses some blue-print information. Eventually there is simply not enough DNA information available to complete any sort of division? The Hayflick Limit indicates the need to slow down the rate of cell division if we want to live long. Cell division can be slowed down by diet and lifestyle etc., but it is also surmised that cell-division can be improved.
Healthspan
The number of healthy years in your life. It includes years free of illness and debilitating conditions and years of wellness (years with a good quality of life).
Lymphoma and leukemia
These two classes of cancer arise from hematopoietic (blood- forming) cells that leave the marrow and tend to mature in the lymph nodes and blood, respectively.
Telomerase and Cancer
Thus, clinical telomerase research is currently focused on the development of methods for the accurate diagnosis of cancer and on novel anti-telomerase cancer therapeutics Most human cancers have short telomeres and express high levels of telomerase, whereas in most normal somatic tissues telomerase is absent
What would happen if you could clear age-related accumulation of defects?
Yes the cell is rejuvenated Yeast as a model: keep generating daughter cells (focus on the mother cell→ senescence→ after 20 generations cell death) Daughter cells are "immortal" keep dividing What is the driving force that keep daughter cell young and healthy? Mother's cell lysosomes become less acidic as cell ages Yeast scars from budding tells chronological age Increase over time Pma1: proton pump of ion in membrane (pH drops) In daughter cell: expression is low (high acidity in vacuoles) Low acidity in mother cell leads to aging Find by knocking out gene in mother and look at the lifespan→ 20 generations **lysosome and vacuole are important in maintaining homeostasis
Diet, APOE4 and Timing
Younger (mean age 35) cognitively unimpaired APOE4 carriers have an increase in brain DHA uptake by PET, suggesting compensation for brain DHA deficiency state and implies vulnerability to a low DHA diet. This suggests that it would take several years to remodel brain DHA after supplementation Being in the lowest quartile of serum DHA/ consuming less than one serving of fatty fish per week increases AD risk
Biomarkers of aging
appearance, metabolic wear and tear (regulation of blood sugar), oxidative metabolism, illnesses of old age External biomarkers (i.e. wrinkled skin, loss of muscle mass) Cellular biomarkers Decreased repair Increased damage Increased lipofuscin For metabolism or cardiovascular (blood pressure can measure cardiovascular activity) as well, chronic inflammation, etc.
Bacterial ROS receptors
bacteria has specific proteins that recognize ROS--> turn on transcription machinery to remove ROS (bind to oxyanion ion can cause transcription factor to bind to DNA)
Wiedmann-Rautenstrauch Syndrome
is characterized by an aged appearance at birth.
drug-induced senescence
drugs to induce senescence
Physiological senescence
embryonic development wound healing tissue remodelling
Mitochondria phenotype with age
experiment with worms: Newborn worm has elongated mitochondria Over time you see less intensity and circular/fragmented mitochondria Some cells lose mitochondria due to accumulation of damage Lower temperature: live longer experiment Lower temperature: more elongated form Age-related change in animals in high related temperature than lower Mitochondria is correlated but not predictive of lifespan
Mitochondria and aging
function of mitochondria declines with age mitochondrial peptide produced by mitochondrial DNA (humanim and MOTS-c) go to mutliple organs and body.
What factors affect lifespan
geography, social status, social determinants, genes, environment
Extrinsic apoptosis
induced by other cells (killer and T lymphocytes)
iPSC
induced pluripotent stem cells, reversal of a multipotent cell to a pluripotent cell Potential for stem-cell like iPSC techniques or transformation People rely on embryonic stem cells for regeneration methods Compare between iPSC and regular stem cells Pretty similar but neuronal differentiation was weaker iPSC and ESC
Studying the mitochondria
mtDNA--> mtRNA--> mito-peptides--> biology--> population data Look at which peptides correspond to disease (Parkinson or Alzheimers) Look at which peptides is affected by mitochondrial variant→ synthesize those peptides in cell lines/mouse models Look at trancsriptome of peptide to see if it affected by snips and look at population data to find association between the mitochondria barrier and peptide
What is the first line of defense against a tumor
natural killer cells
p53 and tumor growth
p53 dependent apoptosis suppresses tumor growth In normal cells proliferate but if mutation→ proliferating (no senescence induced or apoptosis)--> p53→ slow down and cell cycle arrest Mutation in p53 comes later stage of cancer Occur in later stage of adenoma (tumor growth and for chemotherapy) Gamma irradiation and adriamycin (chemotherapy)--> tumor volume declines only if p53 is present Induce apoptosis in tumor cells and kill tumor cells Only works if p53 is present b/c if not cannot induce apoptosis
Rate of living theory
postulates that the faster an organism's metabolism, the shorter its lifespan. Rate of living theory - normal metabolism causes progressive damage (e.g., free radical damage) = aging. Faster metabolism = faster aging Dietary and Caloric restriction decreases metabolism. Mitochondrial mutation slow development and metabolism. Inactivation of mito genes increases lifespan in C. elegans
Mitochondria function
producing energy cell death heat production storing calcium retrograde signaling: Ca2+, ATP, ROS, Ac-CoA, NAD+/NADH, mitochondrial-derived peptides (MDPs) --> cellular effects activation of signaling pathways remodeling of chromatin activation of nuclear genes
What is a gene?
unit of heredity and variation in an organism
Mutagen vs carcinogen
• A factor which brings about a mutation is called amutagen. • A mutagen is mutagenic. • Any agent that causes cancer is called a carcinogen and is described as carcinogenic. • So some mutagens are carcinogenic.
How can we test if ROS is bad?
• Genetically disrupt ETC Should generate ROS from loss of complexes • Add oxidizing agents Should be more toxic. • What is the impact on lifespan i.e. paraquat herbicide to induce ROS, low dose of paraquat--> increase lifespan
Telomerase deficient mice
• Induces DNA damage • Loss and uncapping results in early: • Tissue atrophy • Stem cell depletion • Organ system failure • Impaired tissue repair Remove telomerase genes and look at phenotypes DNA damage, tissue atrophy (brain mass loss), stem cell depletion, organ fails Is this aging?: no because it came since the beginning (premature aging)
Types of carcinogens
• Ionising radiation - X Rays, UV light • Chemicals - tar from cigarettes • Virus infection - papilloma virus can be responsible for cervical cancer. • Hereditary predisposition - Some families are more susceptible to getting certain cancers. Remember you can't inherit cancer its just that you maybe more susceptible to getting it.
Function of telomeres
• They protect the chromosomes. • They separate one chromosome from another in the DNA sequence • Without telomeres, the ends of the chromosomes would be "repaired", leading to chromosome fusion and massive genomic instability. Telomeres are also thought to be the "clock" that regulates how many times an individual cell can divide. Telomeric sequences shorten each time the DNA replicates. Healthy human cells are mortal because they can divide only a finite number of times (Hayflick limit), growing older each time they divide. Thus cells in an elderly person are much older than cells in an infant. Population doubling: telomere length is constant in germ cells but decrease in somatic cells After 40-60 times of population doubling→ senesce Once Hayflick limit is reached→ crisis→ cell death Cell try to ligate end with another chromosome→ genomic instability→ die
Tumor suppressor p53
•The 'guardian of the genome' •The most frequently mutated gene in cancer •Functions as a sequence-specific transcription factor regulating a large number of genes •Responsive to a wide array of signals that stress the cell including: ØDNA damage ØhypoxiaØhyperproliferative signals emanating from oncogenes p53 has many mechanisms of anticancer function, and plays a role in apoptosis, genomic stability, and inhibition of angiogenesis. In its anti- cancer role, p53 works through several mechanisms: - It can activate DNA repair proteins when DNA has sustained damage. - It can induce growth arrest by holding the cell cycle at the G1/S regulation point on DNA damage recognition (if it holds the cell here for long enough, the DNA repair proteins will have time to fix the damage and the cell will be allowed to continue the cell cycle). - It can initiate apoptosis, the programmed cell death, if DNA damage proves to be irreparable.
