PKCβII-induced upregulation of PGP9.5 and VEGF in postoperative persistent pain in rats

Wnt5a in keratinocytes contributes to complex regional pain syndrome through the activation of NR2B and MMP9 in rats

BACKGROUND

Complex regional pain syndrome (CRPS) is a chronic pain condition characterized by inflammatory features, though the underlying mechanisms remain partly understood. Our study examined whether Wnt5a in skin keratinocytes contributes to CRPS-related pain hypersensitivity by activating downstream N-methyl-D-aspartate receptor subunit 2B (NR2B) and matrix metalloproteinase-9 (MMP9) signaling in rats.

METHODS

We developed a cell-culture model to mimic the local inflammation of CRPS and a rat model to mimic the chronic post-ischemia pain experienced by CRPS patients. Mechanical and heat pain thresholds in the hind paw were measured using an electronic von Frey apparatus and a radiant heat device. Western blotting and immunofluorescence were used to examine the expressions of NR2B and MMP9 in the skin and dorsal root ganglion (DRG), and immunofluorescence staining of connexin 43 (Cx43) and protein gene product 9.5 (PGP9.5) were conducted to explore the interaction between keratinocytes and nerve fibers in the skin.

RESULTS

In cell culture, Wnt5a was expressed in keratinocytes and contributed to cellular injury by increasing the levels of NR2B and MMP9. The mechanical and heat pain thresholds measured in the hind paw were decreased in CRPS rats, indicating increased pain sensitivity. The inhibition of Wnt5a alleviated these CRPS-related pain hypersensitivities. High levels of Cx43 and PGP9.5 staining were observed in the epidermis of CRPS rats, suggesting an interaction between keratinocytes and nerve fibers that may contribute to CRPS. Additionally, upregulations of NR2B and MMP9 in the DRG may further exacerbate pain.

CONCLUSIONS

Skin keratinocytes may play an essential role in the pathophysiology of CRPS. Wnt5a signaling may increase pain sensitivity by upregulating downstream NR2B and MMP9, thereby contributing to CRPS.

Skin/muscle incision and retraction regulates the persistent postoperative pain in rats by the Epac1/PKC-βII pathway

Persistent postoperative pain causes influence the life quality of many patients. The Epac/PKC pathway has been indicated to regulate mechanical hyperalgesia. The present study used skin/muscle incision and retraction (SMIR) to induce postoperative pain in rats and evaluated the Epac/PKC pathway in postoperative pain. Mechanical allodynia was assessed by paw withdrawal threshold before and after incision. The levels of Epac, PKC, proinflammatory cytokines, and blood-nerve barrier-related proteins were assessed using Western blotting. We found that SMIR induced the activation of the Epac/PKC pathway, mechanical allodynia, and upregulation of Glut1, VEGF, and PGP9.5 proteins in dorsal root ganglia. Under the influence of agonists of Epac/PKC, normal rats showed mechanical allodynia and increased Glut1, VEGF, and PGP9.5 proteins. After inhibition of Epac1 in rats with SMIR, mechanical allodynia was alleviated, and proinflammatory cytokines and Glut1, VEGF, and PGP9.5 proteins were decreased. Moreover, dorsal root ganglia neurons showed abnormal proliferation under the activation of the Epac/PKC pathway. Using Captopril to protect vascular endothelial cells after SMIR had a positive effect on postoperative pain. In conclusion, SMIR regulates the persistent postoperative pain in rats by the Epac/PKC pathway.

Protective Roles of Apigenin Against Cardiometabolic Diseases: A Systematic Review

Apigenin is a flavonoid with antioxidant, anti-inflammatory, and anti-apoptotic activity. In this study, the potential effects of apigenin on cardiometabolic diseases were investigated in vivo and in vitro. Potential signaling networks in different cell types induced by apigenin were identified, suggesting that the molecular mechanisms of apigenin in cardiometabolic diseases vary with cell types. Additionally, the mechanisms of apigenin-induced biological response in different cardiometabolic diseases were analyzed, including obesity, diabetes, hypertension and cardiovascular diseases. This review provides novel insights into the potential role of apigenin in cardiometabolic diseases.

Regulation of CaV3.2 channels by the receptor for activated C kinase 1 (Rack-1)

This study describes the interaction between Ca_V3.2 calcium channels and the receptor for activated C kinase 1 (Rack-1), a scaffold protein which has recently been implicated in neuropathic pain. The coexpression of Ca_V3.2 and Rack-1 in tsA-201 cells led to a reduction in the magnitude of whole-cell Ca_V3.2 currents and Ca_V3.2 channel expression at the plasma membrane. Co-immunoprecipitations from transfected cells show the formation of a molecular protein complex between Cav3.2 channels and Rack-1. We determined that the interaction of Rack-1 occurs at the intracellular II-III loop and the C-terminus of the channel. Finally, the coexpression of PKCβII abolished the effect of Rack-1 on current densities. Altogether, our findings show that Rack-1 regulates Ca_V3.2-mediated calcium entry in a PKC-dependent manner.