Carbon monoxide-releasing vesicles provide rapid and sustained inhibition of inflammatory pain in mice

Carbon monoxide (CO) is an important modulator of chronic pain, but its clinical use remains limited. To enhance its therapeutic potential, we developed a vesicular CO-releasing system based on a carbonyl metallosurfactant (PCOL6) and soy phosphatidylcholine (SPC) and evaluated its physicochemical properties, as well as its in silico and in vivo effects on inflammation-induced nociception and muscle impairment in male C57BL/6 mice. The metallosomes exhibited a uniform size distribution, stability upon dilution, and a predominantly single membrane, indicating their suitability for therapeutic applications. Computational simulations revealed that PCOL6 can mix with phospholipids to form stable lamellar structures with thinner and more disordered bilayers than those of pure phospholipid membranes. In vivo experiments showed that acute administration of PCOL6/SPC vesicles inhibited complete Freund’s adjuvant (CFA)-induced allodynia faster and longer than tricarbonyldichlororuthenium (II) dimer, Ru2Cl4(CO)6 (CORM-2). Repeated metallosome treatment was also more effective than CORM-2 at reducing allodynia, hyperalgesia, and inflammation-related muscle deficits. Both CO releasers normalized CFA-induced NOD-like receptor protein 3 inflammasome overexpression, increased heme oxygenase 1 (HO-1) and NAD(P)H quinone dehydrogenase 1 expression, and maintained elevated superoxide dismutase 1 levels in paw tissues; notably, HO-1 induction was greater in PCOL6/SPC-treated mice. These findings suggest that PCOL6/SPC metallosomes represent a promising therapeutic strategy for chronic inflammatory pain.