A new hope for neurodegeneration: possible role of hydrogen sulfide.

For hundreds of years, hydrogen sulfide (H2S) has been known solely as a toxic gas with the smell of rotten eggs. Nevertheless, the notoriety of H2S as a toxic gas is experiencing a transformation, with an increasing amount of research showing that it regulates a range of physiological and pathological processes in mammals. Hence H2S is a physiologically important molecule and has been referred to as the third gaseous mediator alongside nitric oxide and carbon monoxide. This past decade has seen an exponential growth of scientific interest in the physiological and pathological significance of H2S. In particular, in the central nervous system, H2S facilitates long-term potentiation and regulates intracellular calcium concentration and pH level in brain cells. Interestingly, H2S may exert antioxidant, anti-apoptotic, and anti-inflammatory effects which are related to neurodegenerative disorders such as Alzheimer's disease (AD), Parkinson's disease (PD), and vascular dementia. Meanwhile, abnormal generation and metabolism of H2S are involved in most of these neurodegenerative disorders. This review presents current knowledge of H2S and its neuroprotective effects in neurodegenerative disorders, with a special emphasis on AD and PD. It is concluded that a H2S-modulated agent will be a new hope for neurodegenerative disorders including AD and PD.