Recent advances in molecular pathways and therapeutic implications targeting neuroinflammation for Alzheimer's disease

Alzheimer's disease (AD) is a major contributor of dementia leading to the degeneration of neurons in the brain with major symptoms like loss of memory and learning. Many evidences suggest the involvement of neuroinflammation in the pathology of AD. Cytokines including TNF-alpha and IL-6 are also found increasing the BACE1 activity and expression of NF kappa B resulting in generation of A beta in AD brain. Following the interaction of A beta with microglia and astrocytes, other inflammatory molecules also get translocated to the site of inflammation by chemotaxis and exaggerate neuroinflammation. Various pathways like NF kappa B, p38 MAPK, Akt/mTOR, caspase, nitric oxide and COX trigger microglia to release inflammatory cytokines. PPAR gamma agonists like pioglitazone increases the phagocytosis of A beta and reduces inflammatory cytokine IL-1 beta. Celecoxib and roficoxib like selective COX-2 inhibitors also ameliorate neuroinflammation. Non-selective COX inhibitor indomethacin is also potent inhibitor of inflammatory mediators released from microglia. Mitophagy process is considered quite helpful in reducing inflammation due to microglia as it promotes the phagocytosis of over activated microglial cells and other inflammatory cells. Mitophagy induction is also beneficial in the removal of damaged mitochondria and reduction of infiltration of inflammatory molecules at the site of accumulation of the damaged mitochondria. Targeting these pathways and eventually ameliorating the activation of microglia can mitigate neuroinflammation and come out as a better therapeutic option for the treatment of Alzheimer's disease.