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Life Extension Magazine

Life Extension Magazine April 2011
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University of California Researchers Restore Immune Function in Aging Human Cells

By Delia Wilder
University of California Researchers Restore Immune Function in Aging Human Cells

An analog of a previously banned drug may have yielded a significant age-reversal breakthrough.

Aging of the immune system, known as immunosenescence, plays a central role in the overall degeneration of the human body. (See article Innovative Strategy for Combating Immunosenescence)

Scientists at the University of California San Francisco and the National Institute on Aging1 have successfully reversed age-related deterioration in immune cell function using lenalidomide, a relative of the infamous drug thalidomide.

In older humans, decreased generation of cell signaling molecules like interferon-gamma (IFN-gamma) by white blood cells reduces the ability of the aging immune system to kill intracellular microbes and eliminate cancer cells.2

Lenalidomide provides intriguing immune-boosting properties, including an increase in production of cell signaling molecules that mobilize vital immune system cells like T-helper white blood cells and natural killer cells. In fact, recent scientific data shows that lenalidomide helps to normalize output of critical immune signaling molecules like interferon-gamma and IL-2, known to be reduced in white blood cells taken from individuals 65 and older.1

Even more remarkable, these effects were observed at exceedingly low doses. This study has huge implications. We need normally functioning immune cells to fend off cancer and infection as we mature—precisely the kinds of conditions to which many people succumb as they and their immune systems decline with aging.

In this article, the results of this groundbreaking study are detailed. You will also learn how these findings relate to your immune system’s health and function.

New Benefits from an Old Drug

The UCSF Study of Lenalidomide and Aging
Cancer Cell

In the late 1950s and early ‘60s, thousands of children suffered severe birth defects after their mothers took thalidomide, a sedative then used to prevent nausea in pregnancy.3 That catastrophe led to the complete withdrawal of the drug from the market worldwide and stifled research investigation into beneficial immune-boosting properties of the drug over the following thirty years. At the start of the new millennium, however, scientific interest was reawakened as scientists studied thalidomide’s impact on the immune system in certain skin conditions.4

Given the teratogenic effects (i.e., birth defects) caused by thalidomide, new research began to focus upon “second-generation” drugs.5 As a result, lenalidomide has significantly changed the management of diseases such as multiple myeloma, myelodysplastic syndrome, and some leukemias, all of which arise from disruptions of the T- and B-cell command and control system.5-10 The drug is now also finding a role in management of certain challenging solid tumors such as those of the kidney and lung.11-14

Lenalidomide directly kills cancer cells and limits tumor growth.8,15-17 It is the drug’s immunomodulatory potential, however, that attracted the attention of the UCSF researchers.1

Lenalidomide specifically stimulates T-helper and natural killer cells, in large part by promoting production of cytokine IL-2.6 Research clearly indicates that aging is associated with reduced levels of both IL-2 and the IL-2 receptor on cell surfaces. For example, comparison of white blood cells from younger donors (less than 40 years of age) with older donors (greater than 60 years of age) shows reduced levels of both IL-2 and the IL-2 receptor.18

IL-2 helps T-helper and natural killer cells against invading infectious agents such as bacteria and viruses. Lenalidomide also inhibits T-suppressor cells that prematurely shut down immune function, thus allowing cytotoxic and natural killer cells to exert their beneficial effects against cancer cells.14 Lenalidomide has potent immunomodulatory effects upon inflammation.16,19 For example, lenalidomide inhibits production of pro-inflammatory cytokines like TNF-alpha, IL-1, IL-6, and IL-12 and elevates the production of the anti-inflammatory cytokine IL-10 from human white blood cells.20

What does all this have to do with aging? Plenty, when we remember that immunosenescence involves decreases in the very T-cell numbers and functions that lenalidomide enhances. That’s what led Dr. Edward J. Goetzl and his team at UCSF to explore lenalidomide for the first time as an anti-immunosenescence drug.

The UCSF Study of Lenalidomide and Aging

Dr. Goetzl is a world-renowned expert in human aging and an immunologist. When Dr. Goetzl and his team explored the benefits of lenalidomide on cancer, it led to their breakthrough work demonstrating lenalidomide’s astonishing effects on immunosenescent cells.1

The team obtained T-cells from a group of healthy young adults aged 21-40 years, and also from adults 65 years and older. They stimulated the T-cells to mimic an infection or invader, using standard laboratory techniques. Next, they incubated the stimulated cells with lenalidomide, keeping some stimulated T-cells untreated as controls. Finally, they measured a host of T-cell functions along with other factors.1

The results from their study may change the direction of treatment for the aging immune system.

Lenalidomide-treated T-cells from young subjects increased their IL-2 production 17-fold, and that of IFN-gamma 3-fold, a remarkable increase. However, the same concentrations of lenalidomide, used to treat T-cells from the older subjects, produced an astonishing 120-fold increase in IL-2, and a 6-fold increase in IFN-gamma. What these results mean is that lenalidomide restores and sustains levels of the very cells and cytokines that otherwise diminish with aging.

That’s not all. Lenalidomide increased production of helper T-cells from older subjects, and suppressed the apoptosis to which older people’s T-cells are especially vulnerable.1 Furthermore, it restored T-cells’ ability to move toward a chemical stimulus to levels indistinguishable from that of younger subjects’ cells.1 Finally, lenalidomide treatment reduced production of the pro-inflammatory cytokine TNF-alpha from other immune cells called macrophages.

Cancer treatment regimens use doses as high as 50 mg/day for several weeks at a time.7 But the dosing of lenalidomide used in the UCSF study were estimated to be equivalent to those attainable by oral doses of just 1-3 mg, and they produced their beneficial effects for up to 5 days after a single treatment.1

Acknowledging the astounding results of lenalidomide treatment at such tiny doses, Dr. Goetzl recently said, “If you could take a low-dosage pill with no side effects, wouldn’t you do it?”21

The team has big plans for next steps. Concluding the report of this first study, they write, “Future testing of low-dose lenalidomide will focus on its potential roles in improving diverse aspects of immunity in the elderly population, ranging from the effectiveness of vaccines to host defenses against microbial infections to resistance to cancers.”1

What You Need to Know: UCSF Scientists Restore Immune Function in Aging Human Cells
  • UCSF Scientists Restore Immune Function in Aging Human Cells
    Older adults have increased susceptibility to infections and cancers compared with younger people.
  • That increased vulnerability is the result of age-related degradation of the human immune system’s function in the process known as immunosenescence.
  • Immunosenescence produces decreased responsiveness of vital immune cells called T-cells, which hold the reins of the command-and-control system governing human immunity.
  • As T-cell function declines, levels of important protective cytokines plummet, resulting in further T-cell dysfunction and impaired immune responses to microbes and cancerous cells.
  • A drug called lenalidomide, originally developed for use in cancer treatment, has remarkable abilities to reverse many components of T-cell-related immunosenescence.
  • A recent study dramatically proved that lenalidomide increases key cell-signaling molecules in older adults’ white blood cells by as much as 120-fold, and it can restore certain T-cell functions to levels very similar with those of healthy young adults.
  • Although lenalidomide is chemically related to thalidomide, it has fewer toxic side effects even at chemotherapy doses; the recent study used substantially lower concentrations of the drug, equivalent to small oral doses.
  • Lenalidomide is expected to change the way we think of immunosenescence, relegating it to the level of a treatable consequence, not an inevitable cause, of aging.

The Implications

So how might low-dose lenalidomide help the aging immune system?

The answer is it may help restore cell signaling of the aging immune system to the level of a healthy young adult. For example, young people get cancer at a small fraction of the rates of older adults. One reason is the steady patrolling of the young person’s body by a healthy, vigorous immune system. The youthful immune system “looks for” aberrant, potentially cancerous cells and destroys them before they can proliferate out of control. As another example, infection from influenza (“the flu”) and bacterial pneumonia can be quite dangerous in the elderly, while younger individuals suffer from far less mortality from these types of infectious diseases. An important reason for this difference is the vigorous response of the youthful immune system toward invading microbes in contrast to the sluggish response of the aging immune system.

The Implications

However, more work needs to be done to better understand lenalidomide’s effects upon the immune system before widespread use for immunosenescence treatment in aging humans.

For example, low-dose lenalidomide seemed to have different effects upon IL-17 in younger vs. older human test subjects’ white blood cells.1 The implications are that low-dose lenalidomide in older subjects would not be expected to impair recruitment of neutrophils (a type of white blood cell), nor increase the risk of immune system attacking healthy tissues (autoimmunity) through excessive mobilization and activation of T-helper cells and related subsets of T-effector cells. Clearly, more work needs to be done to understand the benefits and limitations of low-dose lenalidomide on the aging immune system in humans.

The concept of immunosenescence explains why the aging immune system gradually weakens and leaves us vulnerable. Lenalidomide in low doses appears to hold promise for restoring the aging immune system to more youthful, vibrant function.

Summary

The progressive deterioration of the immune system with age, known as immunosenescence, has long been assumed to be inevitable. It underlies the cause of death in the majority of older adults, especially the very old, who succumb to infections and cancers that a vigorous, healthy immune system can resist. Thanks to the work of Dr. Edward J. Goetzl and his devoted team of scientists, however, immunosenescence may soon take its place among the growing list of treatable consequences of aging. Their work with lenalidomide demonstrates the potential power of immunomodulation using tiny doses of a drug. Their recent study suggests that lenalidomide can boost age-related impairments in the all-important T-helper and natural killer cell populations, while tamping down the activity of T-regulatory cells that would otherwise suppress immune function. Astonishingly, low-dose lenalidomide can restore some T-cell functions to levels identical with those of healthy young adults. Although more work needs to be done to fully understand the benefits and risks associated with low-dose lenalidomide, Dr. Goetzl’s work holds great promise to usher in a new age of discovery and research sure to benefit older people with evidence of immunosenescence.

If you have any questions on the scientific content of this article, please call a Life Extension® Health Advisor at 1-866-864-3027.

Understanding the Immune System

The human immune system tirelessly protects us against microscopic invaders. Without it, we rapidly succumb to otherwise innocuous agents such as viruses, bacteria, and fungi, and develop cancerous cells as well.22 While most young adults have a robust immune system, the picture darkens after that, as the immune system begins a gradual and apparently inevitable decline.22,23 As a result of this system-wide degradation, older adults grow increasingly vulnerable to new infections and autopsy studies confirm infection as a major cause of death in the very old.22 Older people are also subject to recurrence of former infections, to development of cancers, and to autoimmune diseases and inflammation.23-25 Together these changes are known as “immunosenescence,” the aging of immunity.23 During the process of immunosenescence, which begins as early as age 60, virtually every element of the immune system becomes impaired.1,23,26,27 Many experts believe immune function over the course of your life is a core determinant of longevity.24,28

Human immunity involves a complex system of interacting components, including cells known as macrophages, dendritic cells, natural killer (NK) cells, and the B- and T-cells.1 B-cells produce the antibodies that identify and neutralize invaders. T-cells, on the other hand, interact with the other elements of the system to communicate threats and coordinate response. Some T-cells are also directly involved in attacking and destroying virally infected cells and those with cancerous characteristics.

As we age, T-cell function decreases in various key areas. Vital T-cell receptor (TCR) proteins lose their ability to connect to antigen-presenting cells.29 Helper T-cells produce less of the IL-2 and IFN-gamma cytokines they use to communicate to other immune cells about invaders.30,31 They also become less responsive to cytokines themselves, failing to reproduce in response to signals from other cells.31,32

Even the number of new recruits (the so-called “naïve” T-cells) drops, preventing the immune system from fielding fresh troops.24,33 In addition, T-cells of older individuals are at high risk for the cellular suicide known as apoptosis, further diminishing the system’s readiness.22 Scientists theorize that it is the multimodal decline of our immune system that results in a decreased life span.34

The number of “memory” T-cells, critical for respoding to new exposure to known infections, also diminishes with age, which accounts for the reduced response to vaccines in older adults.24 And the assassins of the T-cell world, natural killer (NK) cells, also struggle to identify and destroy viruses and incipient cancer cells.

Some of the most profound effects of immunosenescence involve regulatory T-suppressor cells, however, which increase in number and activity.1,35,36 This results in reduced function of the rest of the T-cell-mediated immune response. Ultimately, predominance of these regulatory suppressor cells impairs our response to new infections, promotes reactivation of chronic infections (such as painful shingles), and increases our vulnerability to many cancers.37

For all of these reasons, then, scientists are profoundly interested in identifying means of reversing the changes brought on by immunosenescence and restoring immune responses to a more youthful profile. Lenalidomide is literally changing the rules of the game through its remarkable abilities to do just that.

References

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