Zinc Gluconate-Loaded Chitosan Nanoparticles Reduce Severity of Collagen-Induced Arthritis in Wistar Rats

Rheumatoid arthritis (RA) is the most prevalent autoimmune disease affecting about 1% world population. Zinc (Zn) is necessary for the maintenance of bone homeostasis and the level of Zn was reported to be decreased in RA patients and collagen-induced arthritic rats. Effective delivery of Zn has been reported using zinc gluconate but oral absorption of Zn from zinc gluconate (ZG) is very low in humans. Zn supplementation reduces disease severity in patients suffering from chronic, refractory RA and exerts mild and transient side effects. The aim of this study was to synthesize and characterize zinc gluconate-loaded chitosan nanoparticles (ZG-Chit NPs) and to evaluate and compare therapeutic efficacy of ZG-Chit NPs and zinc gluconate against collagen-induced RA in Wistar rats. The nanoparticles were formulated by ionic gelation method and the hydrodynamic diameter was 106.5 +/- 79.55 nm as measured using DLS. The particle size, shape, and surface morphology was further confirmed by transmission electron microscopy, scanning electron microscopy, and atomic force microscopy. These nanoparticles showed good cytocompatibility against foreskin fibroblasts (BJ) and L929 cells. Arthritic rats were treated with ZG (20 mg/kg body weight, intraperitoneally) and equivalent doses of ZG-Chit NPs. The treatment of both ZG and ZG-Chit NPs reduced the severity of arthritis as evidenced by reduced joint swelling, erythema, and edema but ZG-Chit NPs exhibited superior efficacy. Furthermore, it was found that ZG and ZG-Chit NPs attenuate biomarkers of inflammation (C-reactive protein, myeloperoxidase, nitric oxide, TNF-alpha, and IL-1 beta) and oxidative stress (articular elastase, lipid peroxidation, catalase, glutathione, and superoxide dismutase). The results of the histopathology further confirmed that ZG-Chit NPs markedly suppressed infiltration of inflammatory cells as compared to ZG at the ankle joint tissue. Immunohistochemical analysis also revealed that treatment with ZG-Chit NPs resulted in reduced pro-inflammatory marker (TNF-alpha, IL-6, and iNOS) expression and enhanced SOD1 expression. Overall, this study suggests that ZG and ZG-Chit NPs suppressed the severity of arthritis plausibly mediated by attenuation of inflammation and oxidative stress and more importantly ZG-Chit NPs exhibited superior efficacy as compared to ZG.