Neuroprotective role of morin hydrate on 3-nitropropionic acid-elicited huntington's disease: in vivo investigation of RIPK1/RIPK3/MLKL necroptosis signaling pathway.

Background: Huntington's disease (HD) is a rare dominantly inheritable autosomal neurodegenerative disease with unclear pathophysiological pathways. In neurodegenerative disorders, including HD, necroptosis plays a significant role in neuronal death. Morin hydrate (MH), a natural bioactive flavonoid, has various pharmacological properties via orchestrating neuroinflammation, apoptosis, and necroptosis. Up to now, there is no extant data on the impact of MH on the necroptotic pathway in HD.

Aim: This research aimed to scrutinize the effect of MH on neurodegeneration initiated by 3-nitropropionic acid (3-NP) administration in rats via modulating necroptosis and apoptosis signaling pathways and compare it with necrosulfonamide (NSA) as a necroptosis inhibitor.

Methods: HD was triggered in male wistar rats by intraperitoneal injection of 3-NP (10 mg/kg/day) for 14 days. Intraperitoneal injection of MH (20 mg/kg/day, i.p.) or NSA (1.65 mg/kg/day, i.p.) an hour prior to 3-NP administration for 14 days. At the end of study, rats were weighed, and their locomotor activity was assessed via grip strength and open field tests. Striata of rats were investigated histologically and immunohistochemically by evaluation the expression levels of glial fibrillary acidic protein (GFAP). Striatal tumor necrosis factor-alpha (TNF-α), caspase 3, and 8 levels were quantified through the ELISA technique, while striatal expression of necroptosis-associated proteins; phosphorylated form of receptor interacting protein kinase 1/3(p-RIPK1, p-RIPK3) and phosphorylated form of mixed lineage kinase domain-like protein (p-MLKL) were assessed by the Western blot technique. Striatal succinate dehydrogenase (SDH) activity was assayed colorimetrically. Finally, gene enrichment analysis using ShinyGO was employed.

Results: MH and NSA significantly mitigated body weight loss and ameliorated locomotor deterioration, besides reversing histological abnormalities in the striatum of rats. Intriguingly, MH exerted similar effects on specific biomarkers and molecular signals as NSA. MH and NSA inhibited neuroinflammation, apoptosis, and necroptosis by significantly decreasing the striatal (TNF-α), caspase 3, and necroptosis-associated proteins (P-RIPK1, P-RIPK3, and P-MLKL) levels. Besides, MH and NSA also decreased striatal GFAP and increased SDH activity. Gene enrichment analysis revealed a significant interaction between genes. Together, MH exerts a neuroprotective action on 3-NP-elicited HD rats via reducing neuroinflammation, apoptosis, and necroptosis. This study highlights MH as a potential protection against HD, calling for further research to confirm its neuroprotective effects.