Pathological and Therapeutic Advances in Parkinson's Disease: Mitochondria in the Interplay

Abstract

Parkinson's disease (PD) is the second most common neurodegenerative illness majorly affecting the population between the ages of 55 to 65 years. Progressive dopaminergic neuronal loss and the collective assemblage of misfolded alpha-synuclein in the substantia nigra, remain notable neuro-pathological hallmarks of the disease. Multitudes of mechanistic pathways have been proposed in attempts to unravel the pathogenesis of PD but still, it remains elusive. The convergence of PD pathology is found in organelle dysfunction where mitochondria remain a major contributor. Mitochondrial processes like bioenergetics, mitochondrial dynamics, and mitophagy are under strict regulation by the mitochondrial genome and nuclear genome. These processes aggravate neurodegenerative activities upon alteration through neuroinflammation, oxidative damage, apoptosis, and proteostatic stress. Therefore, the mitochondria have grabbed a central position in the patho-mechanistic exploration of neurodegenerative diseases like PD. The management of PD remains a challenge to physicians to date, due to the variable therapeutic response of patients and the limitation of conventional chemical agents which only offer symptomatic relief with minimal to no disease-modifying effect. This review describes the patho-mechanistic pathways involved in PD not only limited to protein dyshomeostasis and oxidative stress, but explicit attention has been drawn to exploring mechanisms like organelle dysfunction, primarily mitochondria and mitochondrial genome influence, while delineating the newer exploratory targets such as GBA1, GLP, LRRK2, and miRNAs and therapeutic agents targeting them.

Keywords: Autophagy; Parkinson’s disease; mitochondrial dysfunction; mitogenome; neuroinflammation; oxidative stress.

Fig. 1

PD Pathological Cascade in Substantia Nigra. The above complex cascade shows the interplay of factors like aging, oxidative stress, environmental factors, and altered physiological signaling between cells. Neuroinflammatory process begins majorly due to cellular oxidative damage leading to microglial activation and cytokine infiltration and further inflammatory damage. Proteostasis is altered owing to genetic mutations (SNCA, PINK1, etc.), environmental stressors and oxidative damage leading to Lewy body inclusions. The apoptotic signaling is activated by excitotoxic damage to the neurons and mitochondrial dysfunction leading to caspase activation occurs. These processes cumulatively result in the manifestation of neurodegeneration and hence neuronal death, aggravating the PD condition.

Fig. 2

Neuroinflammation associated to mitochondrial-DAMPs.