Treatment with slow-releasing hydrogen sulfide donors inhibits the nociceptive and depressive-like behaviours accompanying chronic neuropathic pain: Endogenous antioxidant system activation

Background: Therapies to treat chronic neuropathic pain and its associated comorbidities are limited. Recent studies demonstrated that the administration of slow-releasing hydrogen sulfide (H 2 S) donors inhibited chemotherapy-induced neuropathic pain. However, the antidepressant or anxiolytic effects of these compounds and their mechanisms of action during chronic neuropathic pain have not been evaluated. Aims: To determine whether the administration of two slow-releasing H 2 S donors, allyl isothiocyanate (A-ITC) and phenyl isothiocyanate (P-ITC), inhibits the nociceptive and emotional disorders associated with chronic neuropathic pain. Methods: In C57BL/6 male mice with neuropathic pain caused by the chronic constriction of the sciatic nerve, we assessed the effects of intraperitoneal administration of A-ITC and P-ITC in (a) the mechanical allodynia, thermal hyperalgesia and thermal allodynia induced by nerve ligation; (b) the anxiety- and depressive-like behaviours linked with neuropathic pain; (c) glial activation and mitogen-activated protein kinases phosphorylation, and (d) expression of the antioxidant enzymes, heme oxygenase 1 (HO-1), NADPH quinone oxidoreductase1, and glutathione S-transferase mu-1 (GSTM1), and alpha-1 (GSTA1), in hippocampus and prefrontal cortex (PFC). Results: Both treatments inhibited the allodynia and hyperalgesia, depressive-like behaviours, astroglial activation, and the extracellular signal-regulated kinase 1/2 phosphorylation but were unable to abolish the anxiety-like behaviours accompanying neuropathic pain. A-ITC and P-ITC also augmented the expression of HO-1, GSTM1, and GSTA1 in the hippocampus and/or PFC. Conclusions: The administration of slow-releasing H 2 S donors might be a promising treatment for the management of chronic neuropathic pain and some associated comorbidities via inhibiting the inflammatory and plasticity changes, and activating the endogenous antioxidant responses.