Spinal SET7/9 may contribute to the maintenance of cancer-induced bone pain in mice

Evidence of the Involvement of Spinal EZH2 in the Development of Bone Cancer Pain in Rats

Introduction

Bone cancer pain (BCP) seriously affects the quality of life of patients with advanced cancer, but effective treatment methods are lacking. This study mainly investigates the role of EZH2 in a well-established BCP model induced by Walker 256 breast cancer cells in rats.

Methods

Female Sprague–Dawley rats of the same age weighing approximately 160 g were selected for the experiment. The BCP model was established by injecting inactivated Walker 256 breast cancer cells into the tibia. von Frey filaments were used to measure the paw withdrawal threshold, and bone destruction in the rat was observed using x-ray. The spinal EZH2 and H3K27Tm levels were measured using Western blotting and RT–qPCR analysis. Intrathecal injection of an EZH2 inhibitor was performed to examine the role of EZH2 in trigeminal BCP.

Results

Experimental results showed that injecting Walker 256 breast cancer cells into the tibia induced bone cancer pain. Spinal EZH2 and H3K27Tm levels were significantly increased over time in BCP rats. An intrathecal injection of 3-deazaneplanocin A (DZNep), a selective EZH2 inhibitor, downregulated the expression of EZH2 and attenuate the BCP-induced mechanical allodynia state.

Conclusion

Intrathecal injection of DZNep relieve bone cancer pain in rats. EZH2 expressed in spinal cord tissue may be involved in the process of bone cancer pain in rats.

Role of SET7/9 in the progression of ischemic renal injury in diabetic and non-diabetic rats

SET domain with lysine methyltransferase 7/9 (Set7/9), a histone lysine methyltransferase (HMT), recently suggested to exert a critical role among kidney disorders, whereas its role in diabetes associated IRI co-morbidity remains complete elusive. The present study aimed to understand the role of SET7/9 and histone methylation in regulation of inflammatory signaling under IRI in diabetes mellitus and non-diabetic rats. Our results demonstrated that IRI caused renal dysfunction via increased blood urea nitrogen (BUN) levels in ND and DM rats. The NF-κB mediated inflammatory cascade like increased p-NF-κB, reduced IκBα levels followed by enhanced leukocyte infiltration as shown by increased MCP-1 expressions. IRI results in increased histone H3 methylation at lysine 4 and 36 (H3K4Me2, H3K36Me2), and decreased histone H3 methylation at lysine 9. Additionally, IRI increased the protein and mRNA expression of H3K4Me2 specific histone methyltransferase-SET7/9 in DM and ND rats. The abovementioned results remain prominent in DM rats compared to ND rats followed by IRI. Further, treatment with a novel SET7/9 inhibitor; cyproheptadine, significantly improved renal functioning via reducing the BUN levels in ND and DM rats. Hence, this study demonstrated the role of SET7/9 in mediating active transcription via H3K4Me2, ultimately regulated the NFκB-mediated inflammatory cascade. Therefore, SET7/9 can be explored as novel target for drug development against IRI under DM and ND conditions.

Evidence of the involvement of spinal αB-crystallin in the maintenance of bone cancer pain in rats

BACKGROUND

αB-crystallin (CRYAB) is a small heat shock protein that is able to inhibit neuroinflammatory responses under various pathological conditions. Some studies have proven that neuroinflammatory mechanisms play important roles in bone cancer pain (BCP). However, whether CRYAB participates in the maintenance of BCP has not yet been examined.

METHODS

Walker256 tumour cells were inoculated into the tibia to induce a rat model of BCP. Von Frey hairs were used to measure mechanical allodynia. Immunohistochemistry and western blotting were used to examine the expression level of CRYAB in the spinal dorsal horn.

RESULTS

The gradual development of mechanical allodynia was induced by the injection of Walker256 cells into the tibia. The downregulation of spinal CRYAB expression was found in BCP rats. The intrathecal administration of CRYAB (from days 9 to 15 post-inoculation) dose-dependently alleviated mechanical allodynia in BCP rats. Additionally, there were concomitant increases in spinal CRYAB expression and decreases in TNF-α expression.

CONCLUSIONS

Spinal CRYAB may participate in the maintenance of BCP in rats. The findings will help to identify new drugs for the management of BCP.

SETD7 mediates spinal microgliosis and neuropathic pain in a rat model of peripheral nerve injury

Gene transcription regulation is critical for the development of spinal microgliosis and neuropathic pain after peripheral nerve injury. Using a model of chronic constriction injury (CCI) of the sciatic nerve, this study characterized the role of SET domain containing lysine methyltransferase 7 (SETD7) which monomethylates histone H3 lysine 4 (H3K4me1), a marker for active gene transcription. SETD7 protein expression in the spinal dorsal horn ipsilateral to nerve lesion was increased from one day to 14 days after CCI, concomitantly with the expression of inflammatory genes, Ccl2, Il-6 and Il-1β. The CCI-induced SETD7 expression was predominantly localized to microglia, as demonstrated by immunohistochemistry and western blot from magnetic activated cell sorted spinal microglia. SETD7 knockdown by intrathecal lentivirus shRNA delivery prior to CCI prevented spinal microgliosis and neuropathic pain, whereas lentiviral SETD7 transduction exacerbated these symptoms. In addition, SETD7 regulated H3K4me1 level and expression of inflammatory mediators both in CCI rats and in the HAPI rat microglia cell line. Accordingly, PFI-2, a specific inhibitor of SETD7 monomethylation activity, suppressed the lipopolysaccharides-induced amoeboid morphology of primary microglia and the expression of inflammatory genes, Ccl2, Il-6 and Il-1β. Moreover, intrathecal administration of PFI-2 alleviated CCI-induced neuropathic pain. However, this effect was observed in male but not in female rats. These results demonstrate a critical role of SETD7 in the development of spinal microgliosis and neuropathic pain subsequently to peripheral nerve injury. The pharmacological approach further suggests that SETD7 is a new target for the treatment of neuropathic pain. The underlying mechanisms may involve H3K4me1-dependent regulation of inflammatory gene expression in microglia.