Silymarin protected the cerebral tissue from endoplasmic reticulum stress.

Background: Our aim is to explore silymarin's protective effects against endoplasmic reticulum (ER) stress via protein kinase R-like endoplasmic reticulum kinase (PERK) modulation and elucidate potential enriched pathways through in silico analysis of silymarin-associated PERK protein interactors in cerebral ischaemia-reperfusion (IR) injury.

Materials and methods: 30 rats were categorized into three groups: sham, IR and IR + silymarin groups. Cerebral IR damage was not induced. Only the MCA was identified and clamped without further intervention. Sham group received only physiological serum intravenously. IR group, rats were exposed to 2 hours ischaemia and following 3 hours reperfusion. In IR + silymarin group received 1 μg/kg silymarin intravenously (i.v.) before inducing cerebral IR. Cerebral tissues were processed for histological tissue preparation. Hematoxylin-Eosin and PERK immunostaining was applied. In Cytoscape software, we imported and integrated the silymarin and PERK protein-protein interaction networks generated from the STITCH and STRING databases, respectively. Subsequently, Reactome pathway annotation was performed for this intersected network.

Results: In the sham group, neurons were large and round with oval nuclei, and no histopathological changes were observed. In the IR group, neurons and neuroglial cells showed degeneration with pyknotic nuclei, apoptotic bodies, dilated and congested cerebral capillaries, and numerous vacuoles. After silymarin treatment, the IR + silymarin group showed a restoration of normal histology, with more regular neural and neuroglial cells and decreased vessel dilation and congestion. PERK immunoexpression was mainly negative in the sham group, increased in the IR group, and decreased again in the IR + silymarin group. Upon intersecting the interactors of silymarin and PERK, 17 common proteins were identified. Reactome pathway analysis revealed potential impacts of these proteins on key pathways including immune and cytokine signaling, apoptosis, estrogen signaling, and extracellular matrix degradation.

Conclusions: Silymarin's targeting of PERK offers a promising approach to alleviate ER stress and potentially modulate multiple critical pathways in cerebral ischaemia reperfusion, serving as a comprehensive therapeutic strategy for managing cerebral IR injury.