一氧化氮合酶，神经元抑制剂I

"Aging: getting older, exhibiting the signs of age, the decline in the physical (and mental) well-being over time, leading to death. Since the beginning of time, man has been obsessed with trying to slow down, stop, or even reverse the signs of aging. Many have gone as far as experimenting with nutritional regimens, eccentric exercises, fantastic rituals, and naturally occurring or synthetic wonder-elements to evade the signs of normal aging. Biologically speaking, what is aging? And what does the latest research tell us about the possibility of discovering the elusive “fountain of youth”? Many advances in our understanding of aging have come from systematic scientific research, and perhaps it holds the key to immortality. Scientifically, aging can be defined as a systems-wide decline in organismal function that occurs over time. This decline occurs as a result of numerous events in the organism, and these events can be classified into nine “hallmarks” of aging, as proposed by López-Otin et al. (2013). Several of the pathologies associated with aging are a direct result of these events going to extremes and may also involve aberrant activation of proliferation signals or hyperactivity. The hallmarks of aging have been defined based on their fulfillment of specific aging related criteria, such as manifestation during normal aging, acceleration of aging if experimentally induced or aggravated, and retardation of aging if prevented or blocked, resulting in increased lifespan. The nine hallmarks of aging are genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, deregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, and altered intercellular communication. The biological processes underlying aging are complex. By understanding the hallmarks in greater detail, we can get closer to developing intervention strategies that can make the aging process less of a decline, and more of a recline."