Silymarin protected the cerebral tissue from endoplasmic reticulum stress

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 ischemia- reperfusion (IR) injury.

30 rats were categorized into three groups: sham, IR, and IR + silymarin. Cerebral IR damage was not induced. Only the MCA was identified and clamped without further intervention. The sham group received only physiological serum intravenously. In the IR group, rats were exposed to 2 hours ischemia and then 3 hours of reperfusion. In the IR + silymarin group the rats received 1 μg/kg silymarin intravenously (i.v.) before induction of cerebral IR. Cerebral tissues were processed for histological tissue preparation. Hematoxylineosin and PERK immunostaining were 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.

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.

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