LP342, a novel histone deacetylase inhibitor, decreases nitro-oxidative stress, mitochondrial dysfunction and hepatic ischaemia/reperfusion injury in mice.

Objectives: Some histone deacetylase (HDAC) isoforms contribute to ischaemia/reperfusion (IR) injury (IRI). Here, we examined whether LP342, the lead candidate of a new generation of hydrazide-based HDAC inhibitors (HDACi), decreases hepatic IRI. Methods: IR was induced by clamping blood vessels to ~70% of the livers of mice for 1 h. Key findings: At 6 h after reperfusion, ALT markedly increased, and wide-spread necrosis, leukocyte infiltration, and apoptosis occurred. LP342 treatment (1 mg/kg, ip) at 20 h or 1 h before ischaemia markedly decreased IRI whereas LP342 treatment upon reperfusion was marginally protective. Nitro-oxidative stress, c-Jun-N-terminal kinase (JNK) activation, and mitochondrial dysfunction contribute to IRI. 4-Hydroxynonenal, 3-nitrotyrosine, inducible nitric oxide synthase (iNOS), JNK activation and Sab binding increased markedly after IR, which LP342 blunted. LP342 also induced thioredoxin-1 expression before and after IR. LP342 also decreased mitochondrial depolarisation as detected by intravital microscopy at 2 h after IR. Lastly, LP342 increased acetylation of both histone-3 (class I HDAC substrate) and NFκB p65 but not tubulin (class II HDAC substrate) before and after IR. Conclusions: This novel HDACi protects against IRI most likely by epigenetic upregulation of antioxidant proteins and post-translational modifications of NFκB thus inhibiting iNOS expression and inflammatory responses.