Apigenin attenuates LPS-induced neurotoxicity and cognitive impairment in mice via promoting mitochondrial fusion/mitophagy: role of SIRT3/PINK1/Parkin pathway

Rationale Alteration of the NAD(+) metabolic pathway is proposed to be implicated in lipopolysaccharide (LPS)-induced neurotoxicity and mitochondrial dysfunction in neurodegenerative diseases. Apigenin, a naturally-occurring flavonoid, has been reported to maintain NAD(+) levels and to preserve various metabolic functions. Objectives This study aimed to explore the effect of apigenin on mitochondrial SIRT3 activity as a mediator through which it could modulate mitochondrial quality control and to protect against intracerebrovascular ICV/LPS-induced neurotoxicity. Methods Mice received apigenin (40 mg/kg; p.o) for 7 consecutive days. One hour after the last dose, LPS (12 mu g/kg, icv) was administered. Results Apigenin robustly guarded against neuronal degenerative changes and maintained a normal count of intact neurons in mice hippocampi. Consequently, it inhibited the deleterious effect of LPS on cognitive functions. Apigenin was effective in preserving the NAD(+)/NADH ratio to boost mitochondrial sirtuin-3 (SIRT3), activity, and ATP production. It conserved normal mitochondrial features via induction of the master regulator of mitochondrial biogenesis, peroxisome proliferator-activated receptor gamma (PPAR gamma) coactivator-1 alpha (PGC-1 alpha), along with mitochondrial transcription factor A (TFAM) and the fusion proteins, mitofusin 2 (MFN2), and optic atrophy-1 (OPA1). Furthermore, it increased phosphatase and tensin homolog (PTEN)-induced putative kinase 1 (PINK1) and parkin expression as well as the microtubule-associated protein 1 light chain 3 II/I ratio (LC3II/I) to induce degradation of unhealthy mitochondria via mitophagy. Conclusions These observations reveal the marked neuroprotective potential of apigenin against LPS-induced neurotoxicity through inhibition of NAD(+) depletion and activation of SIRT3 to maintain adequate mitochondrial homeostasis and function.