Mitigative and anti-inflammatory effects of Trichostatin A against radiation induced gastrointestinal toxicity and gut microbiota alteration in mice

Radiation-induced gastrointestinal injury (RIGI) is a serious side effect of abdominal and pelvic radiotherapy, which often limits the treatment of gastrointestinal and gynaecological cancers. RIGI is also observed during accidental radiological or nuclear scenarios with no approved agents available till date to prevent or mitigate RIGI in humans. Trichostatin A (TSA), an epigenetic modulator, has been currently in clinical trials for cancer treatment and is also well known for its antibiotic and antifungal properties. In this study, partial body (abdominal) irradiation mice model has been used to investigate the mitigative effect of TSA against gastrointestinal toxicity caused by gamma radiation. Mice were checked for alterations in mean body weight, diarrhea incidence, disease activity index and survival against radiation. Structural abnormalities in intestine and changes in microbiota composition were studied by histopathology and 16S rRNA sequencing of fecal samples respectively. Immunoblotting and biochemical assays were performed to check protein nitrosylation, expression of inflammatory mediators, infiltration of inflammatory cells and changes in pro-inflammatory cytokines. TSA administration to C57Bl/6 mice improved radiation induced mean body weight loss, maintained better health score, reduced disease activity index and promoted survival. The 16S rRNA sequencing of fecal DNA demonstrated that TSA influenced the fecal microbiota dynamics with significant alterations in the Firmicutes/Bacteriodetes ratio. TSA effectively mitigated intestinal injury, down-regulated NF-κB, Cox-2, iNOS, inhibited PGE2 and protein nitrosylation levels in irradiated intestine. The upregulation of NLRP3-inflammasome complex and infiltrations of inflammatory cells in the inflamed intestine were also prevented by TSA. Subsequently, the myeloperoxidase activity in intestine alongwith serum IL-18 levels was found reduced. These findings provide evidence that TSA inhibits inflammatory mediators, alleviates gut dysbiosis, and promotes structural restoration of the irradiated intestine. TSA, therefore, can be considered as a potential agent for mitigation of RIGI in humans. Depicting the possible mechanism of action of TSA against radiation induced gastrointestinal injury in mice. Radiation leads to activation of NF-κB, the master regulator of inflammation and it target proteins COX-2 and iNOS. Activation of these key inflammatory mediators further up-regulated NLRP3/inflammosome complex, NO-mediated protein modifications and infiltration of inflammatory cells in the irradiated intestine. Further alterations in diversity and composition of gut microbiota contributed to inflammation and GI injury in presence of radiation. TSA administration post irradiation maintained intestinal integrity, and reduced inflammation. Restoration of gut microbiota dynamics and reduced inflammation by TSA might have mitigated radiation mediated gastrointestinal injury and have contributed to survival against irradiation.