Resveratrol suppresses bone cancer pain in rats by attenuating inflammatory responses through the AMPK/Drp1 signaling.

Bone cancer pain (BCP) is induced by primary bone cancer and secondary bone metastasis. During BCP pathogenesis, activated spinal astrocytes release proinflammatory cytokines, which participate in pain information transmission. In this study, we found that BCP rats showed disruption of trabecular bone structure, mechanical allodynia, and spinal inflammation. Moreover, reduced adenosine monophosphate-activated protein kinase (AMPK) activity, increased mitochondrial fission-associated protein Drp1 GTPase activity accompanied by the dysfunction of mitochondrial function, and abnormal BAX and Bcl-2 expression were found in the spinal cord of BCP rats. Notably, these alterations are reversed by resveratrol (Res) administration. Cell experiment results demonstrated that Res promotes mitochondrial function by activating AMPK, decreasing Drp1 activity, and inhibiting tumor necrosis factor-α-induced mitochondrial membrane potential reduction. Taken together, these results indicate that Res suppresses BCP in rats by attenuation of the inflammatory responses through the AMPK/Drp1 signaling pathway.

Clock gene Per1 regulates the production of CCL2 and interleukin-6 through p38, JNK1 and NF-κB activation in spinal astrocytes.

It has been previously reported that spinal clock genes controlled under circadian rhythm contribute to the regulation of astrocytic function, which in turn is involved in diverse processes such as nociceptive transduction and the induction of inflammation. However, how clock genes expressed in spinal cord astrocytes are associated with the modulation of the inflammatory response is poorly understood. In the current study, the role of Period1 (Per1), one of clock genes, in the expression of chemokine (C-C motif) ligand 2 (CCL2) and interleukin-6 (IL-6), which are typical pro-inflammatory mediators produced by spinal astrocytes, was investigated. It was found that the knockdown of Per1 by using RNA interference led to a significant increase of the expression of CCL2 and IL-6 in cultured rat spinal astrocytes. Moreover, the silencing of the Per1 gene also increased the phosphorylation of p38, c-Jun N-terminal kinase (JNK) 1 and IκBα, and led to the translocation of p65 from the cytosol to the nucleus. The induction of CCL2 and IL-6 was significantly inhibited by treatment with the inhibitors of p38, JNK, and NF-κB. By contrast, the overexpression of PER1 by transfection vector significantly blocked the expression of CCL2 and IL-6, and the activation of p38, JNK, and NF-κB. Together, these results suggest that down-regulation of Per1 induced the phosphorylation of p38 and JNK1 and the subsequent activation of NF-κB, and that these events contribute to neuroinflammatory state in the spinal cord via the induction of the release of inflammatory mediators.

Astrocytes in the spinal cord contributed to acute stress-induced gastric damage via the gap junction protein CX43.

Rat restraint water-immersion stress (RWIS) is a compound stress of high intensity and is widely used to study the pathological mechanisms of stress gastric ulcers. The spinal cord, as a part of the central nervous system, plays a dominant role in the gastrointestinal tract, but whether the spinal cord is involved in rat restraint water-immersion stress (RWIS)-induced gastric mucosal damage has not been reported. In this study, we examined the expression of spinal astrocytic glial fibrillary acidic protein (GFAP), neuronal c-Fos, connexin 43 (Cx43), and p-ERK1/2 during RWIS by immunohistochemistry and Western blotting. In addition, we intrathecally injected the astrocytic toxin L-a-aminoadipate (L-AA), gap junction blocker carbenoxolone (CBX), and ERK1/2 signaling pathway inhibitor PD98059 to explore the role of astrocytes in the spinal cord in RWIS-induced gastric mucosal damage and its possible mechanism in rats. The results showed that the expression of GFAP, c-Fos, Cx43, and p-ERK1/2 was significantly elevated in the spinal cord after RWIS. Intrathecal injection of both the astrocyte toxin L-AA and the gap junction blocker CBX significantly attenuated RWIS-induced gastric mucosal damage and decreased the activation of astrocytes and neurons induced in the spinal cord. Meanwhile, the ERK1/2 signaling pathway inhibitor PD98059 significantly inhibited gastric mucosal damage, gastric motility and RWIS-induced activation of spinal cord neurons and astrocytes. These results suggest that spinal astrocytes may regulate the RWIS-induced activation of neurons via CX43 gap junctions and play a critical role in RWIS-induced gastric mucosa damage through the ERK1/2 signaling pathway.