Whole-animal senescent cytotoxic T cell removal using antibodies linked to magnetic nanoparticles.

A major type of unwanted cells that accumulate in aging are anergic cytotoxic T cells. These cells often have virus-specific T cell receptors, as well as other surface markers that distinguish them from their youthful counterparts, and they are thought to play a major role in the decline of the immune system with age. Here we consider two surface markers thought to define these cells in mice, CD8 and Killer cell lectin-like receptor G1 (KLRG1), and a means we developed to remove these cells from the blood of aged C57BL/6 mice. Using antibodies with magnetic nanoparticles linked to their Fc domains, we first developed a method to use magnets to filter out the unwanted cells from the blood and later constructed a device that does this automatically. We demonstrated that this device could reduce the KLRG1-positive CD8 cell count in aged mouse blood by a factor of 7.3 relative to the total CD8 cell compartment, reaching a level typically seen only in very young animals.

Medical bioremediation of age-related diseases.

Catabolic insufficiency in humans leads to the gradual accumulation of a number of pathogenic compounds associated with age-related diseases, including atherosclerosis, Alzheimer's disease, and macular degeneration. Removal of these compounds is a widely researched therapeutic option, but the use of antibodies and endogenous human enzymes has failed to produce effective treatments, and may pose risks to cellular homeostasis. Another alternative is "medical bioremediation," the use of microbial enzymes to augment missing catabolic functions. The microbial genetic diversity in most natural environments provides a resource that can be mined for enzymes capable of degrading just about any energy-rich organic compound. This review discusses targets for biodegradation, the identification of candidate microbial enzymes, and enzyme-delivery methods.

Medical bioremediation: a concept moving toward reality.

Abstract A major driver of aging is catabolic insufficiency, the inability of our bodies to break down certain substances that accumulate slowly throughout the life span. Even though substance buildup is harmless while we are young, by old age the accumulations can reach a toxic threshold and cause disease. This includes some of the most prevalent diseases in old age-atherosclerosis and macular degeneration. Atherosclerosis is associated with the buildup of cholesterol and its oxidized derivatives (particularly 7-ketocholesterol) in the artery wall. Age-related macular degeneration is associated with carotenoid lipofuscin, primarily the pyridinium bisretinoid A2E. Medical bioremediation is the concept of reversing the substance accumulations by using enzymes from foreign species to break down the substances into forms that relieve the disease-related effect. We report on an enzyme discovery project to survey the availability of microorganisms and enzymes with these abilities. We found that such microorganisms and enzymes exist. We identified numerous bacteria having the ability to transform cholesterol and 7-ketocholesterol. Most of these species initiate the breakdown by same reaction mechanism as cholesterol oxidase, and we have used this enzyme directly to reduce the toxicity of 7-ketocholesterol, the major toxic oxysterol, to cultured human cells. We also discovered that soil fungi, plants, and some bacteria possess peroxidase and carotenoid cleavage oxygenase enzymes that effectively destroy with varied degrees of efficiency and selectivity the carotenoid lipofuscin found in macular degeneration.

Microbial degradation of 7-ketocholesterol.

7-Ketocholesterol (7KC) is an oxidized derivative of cholesterol suspected to be involved in the pathogenesis of atherosclerosis and possibly Alzheimer's disease. While some oxysterols are important biological mediators, 7KC is generally cytotoxic and interferes with cellular homeostasis. Despite recent interest in preventing the accumulation of 7KC in a variety of matrices to avoid adverse biological effects, its microbial degradation has not been previously addressed in the peer-reviewed literature. Thus, the rate and extent of biodegradation of this oxysterol was investigated to bridge this gap. A wide variety of bacteria isolated from soil or activated sludge, including Proteobacterium Y-134, Sphingomonas sp. JEM-1, Nocardia nova, Rhodococcus sp. RHA1, and Pseduomonas aeruginosa, utilized 7KC as a sole carbon and energy source, resulting in its mineralization. Nocardia nova, which is known to produce biosurfactants, was the fastest degrader. This study supports the notion that microbial catabolic enzymes could be exploited to control 7KC levels in potential biotechnological applications for agricultural, environmental, or medical use.

Engineering away lysosomal junk: medical bioremediation.

Atherosclerosis, macular degeneration, and neurodegenerative diseases such as Alzheimer's disease, are associated with the intracellular accumulation of substances that impair cellular function and viability. Reversing this accumulation may be a valuable therapy, but the accumulating substances resist normal cellular catabolism. On the other hand, these substances are naturally degraded in the soil and water by microorganisms. Thus, we propose the concept of "medical bioremediation," which derives from the successful field of in situ environmental bioremediation of petroleum hydrocarbons. In environmental bioremediation, communities of microorganisms mineralize hydrophobic organics using a series of enzymes. In medical bioremediation, we hope to utilize one or several microbial enzymes to degrade the intracellular accumulators enough that they can be cleared from the affected cells. Here, we present preliminary, but promising results for the bacterial biodegradation of 7-ketocholesterol, the main accumulator of foam cells associated with atherosclerosis. In particular, we report on the isolation of several Nocardia strains able to biodegrade 7-ketocholesterol and as an ester of 7-ketocholoesterol. We also outline key intermediates in the biodegradation pathway, a key step towards identifying the key enzymes that may lead to a therapy.

Cellular therapy using microglial cells.

Recent insights into the function and dysfunction of microglia may inform future therapies to combat neurodegeneration. We hypothesise how different aspects of microglial activity including migration, activation, oxidative response, phagocytosis, proteolysis, and replenishment could be targeted by novel therapeutic approaches. A combined approach is suggested, encompassing opsonization and anti-inflammatory strategies in conjunction with an engineering of microglial precursors. Xenoproteases for bioremediation could be used to enhance intracellular and extracellular proteolytic capacity. The capacity of microglial precursors to cross the blood-brain barrier and to home in on sites of neural damage and inflammation might prove to be particularly useful for future therapeutic strategies.

Making the case for human life extension: personal arguments.

In the close to medium future, the life sciences might permit a vast extension of the human life span. I will argue that this is a very desirable development for the individual person. The question whether death is a harm to the dying is irrelevant here. All it takes is that being alive is good for the living person and not being alive is not good for anyone. Thus, living persons who expect to live on happily are rationally required to want to stay alive. Eventual uncertainty whether it will be possible to be happy in the future provides no objection, but rather an incentive to try. This view, however, may be naive in assuming that persons are unchanging entities that exist separately from their psychological information. Objections have been derived from reductionistic views that value our future experiences in a way that declines with time, so that there will be a future point beyond which only negligible value accrues. If we adopt such a view, then we cannot now be concerned to have experiences beyond that point. I argue that these arguments fail to take into account all the reasons we might have to be concerned for the future and all kinds of such concern that come from them. The adoption of a plausible reductionistic account can arguably weaken our concern for the future and certainly change its quality in important ways. But this provides no objection to the desire to live forever, nor to live at all.