The Actions And Mechanisms Of P2X7R And P38MAPK Activation In Mediating Bortezomib-Induced Neuropathic Pain

The proteasome inhibitor bortezomib(BTZ),is a potent and first-line anti-cancer drug for multiple myeloma and other non-solid malignancies.Although it inhibits the development of tumors in severe multiple myeloma or other types,it also exhibits the side effects,including peripheral neuropathy,which due to neurological dysfunction and signal processing dysfunction.It has been suggested that many cytokines may play a role in mediating neuropathic pain,but the underlying molecular mechanism is not fully understood.Recent studies have shown that neuropathic pain is closely related to the purine receptor family(P2X).Purine receptors can activate the MAPK family signaling pathways which includes ERKs,JNKs and p38MAPKs,but the specific regulatory mechanism is not completely clear.In this study,the relationship between P2X7R activation and p38 phosphorylation in dorsal root ganglion(DRG)and spinal dorsal horn(SDH)in the development and maintenance of BTZ-induced neuropathic pain was elucidated.we operated behavioral testing and by investigating the pathogenesis in DRG satellite cells and glial cells in SDH to look insight into the space and time variation between phosphorylated p38 and activated P2X7R.P2X7R/p38MAPK signaling pathway in SGCs of DRG and microglia of SDH might be a potential pharmacological target behind this mechanism as an opportunity to relieve BTZ-induced neuropathic pain.Part ? Activation of P2X7 receptor and p38MAPK pathway in DRG satellite cells mediates the neuropathic pain induced by bortezomibP2X7R activation in DRG satellite cells mediates different pain response Activation of p38MAPK signaling pathway in afferent neurons not only mediates inflammatory response,but also leads to the induction and expansion of neuropathic pain status.This study exhibited the role of P2X7R and p38MAPK in BTZ-induced neuropathic pain.Based on the discussion above,the following experiments were designed:(1)Control group:Rats received peritoneal injection(i.p.)of 0.9%NaCl at the equivalent volume the other groups;(2)inhibitor group:1)BBG group:rats were injected with 50mg/kg BBG intraperitoneally.2)SB203580 group:Rats received SB203580(10?l,i.t.)at a concentration of 10?g/10?l.SB203580 is a selective p38 inhibitor which was used in this experiment aimed to clarify whether this inhibitor alone affects the experimental results.;(3)BTZ group:Rats received BTZ(0.2 mg/kg body weight,i.p.)at a concentration of 0.5 mg/ml for 5 successive days;(4)BTZ+inhibitor group:1)BTZ+BBG group:Rats received BBG(50 mg/kg body weight,i.p.)30 min before BTZ(0.2 mg/kg body weight,i.p.)administration with the corresponding concentration.2)BTZ+SB203580 group:SB20358010?g/10?l was injected intravenously(i.t.)30min before BTZ administration with the corresponding concentration.the paw withdrawal thresholds for mechanical stimuli decreased after BTZ application,Inhibition of P2X7R with Brilliant blue G(BBG)had an effect on mechanical thresholds of BTZ rats,it can also influence the inflammatory factors release,p38MAPK mRNA expression,p-p38 protein expression and p-p38 positive cells expression in DRG cells.Inhibition of p38MAPK with SB203580 in rats can also have an impact on mechanical threshold,lowering inflammatory factor expression level,but the expression of P2X7R was not affected.The results above indicate that p38MAPK,as a downstream molecule of P2X7R,plays an important role in BTZ-induced neuropathic pain.Part ? The relationship between activated p38MAPK pathway and P2X7 receptor in BTZ-induced neuropathy in microglia of spinal dorsal hornMicroglia are a type of glial cell that are the resident macrophages of the brain and spinal cord,play an important role in the development of pain.In the spinal dorsal horn(SDH),P2X7R expression in the microglia are also associated with the nociceptive signaling transmission.In this part,we explored the relationship between the phosphorylation of p38MAPK and P2X7R activation in SDH microglia in BTZ-induced neuropathic pain rats.The experimental groups are consistent with the first part.Results showed that P2X7R inhibitor BBG induced the upregulation of mechanical thresholds and affected inflammatory factor expression and p38MAPK expression,p38MAPK inhibitor SB203580 administration before BTZ application not only affect the mechanical thresholds changes and inflammatory factor release in rats but also can inhibit the upregulation of P2X7R,which indicated in SDH microglia,p38MAPK as a downstream molecule of P2X7R,can also have an effect on P2X7R expression,In addition,the consistency of their changes also indicates that they are in the same signal pathway and their influence is bidirectional.This study may provides a new opportunity for neuropathic pain treatment in the future.