Hypoxia-Induced Signaling Activation in Neurodegenerative Diseases: Targets for New Therapeutic Strategies.

For the maintenance of cellular homeostasis and energy metabolism, an uninterrupted supply of oxygen (O2) is routinely required in the brain. However, under the impaired level of O2 (hypoxia) or reduced blood flow (ischemia), the tissues are not sufficiently oxygenated, which triggers disruption of cellular homeostasis in the brain. Hypoxia is known to have a notable effect on controlling the expression of proteins involved in a broad range of biological processes varying from energy metabolism, erythropoiesis, angiogenesis, neurogenesis to mitochondrial trafficking and autophagy, thus facilitating neuronal cells to endure in deprived O2. On the contrary, hypoxia to the brain is a major source of morbidity and mortality in humans culminating in cognitive impairment, gradual muscle weakness, loss of motor activity, speech deficit, and paralysis as well as other pathological consequences. Further, hypoxia resulting in reduced O2 deliveries to brain tissues is supposed to cause neurodegeneration in both in vivo and in vitro models. Similarly, chronic exposure to hypoxia has also been reportedly involved in defective vessel formation. Such vascular abnormalities lead to altered blood flow, reduced nutrient delivery, and entry of otherwise restricted infiltrates, thereby limiting O2 availability to the brain and causing neurological disabilities. Moreover, the precise mechanistic role played by hypoxia in mediating key processes of the brain and alternatively, in triggering pathological signals associated with neurodegeneration remains mysterious. Therefore, this review elucidates the intricate role played by hypoxia in modulating crucial processes of the brain and their severity in neuronal damage. Additionally, the involvement of numerous pharmacological approaches to compensate hypoxia-induced neuronal damage has also been addressed, which may be considered as a potential therapeutic approach in hypoxia-mediated neurodegeneration.