Naringin and chloroquine combination mitigates chloroquine-resistant parasite-induced malaria pathogenesis by...

Malaria, characterised by inflammation and multi-organ complications, needs novel chemotherapeutics due to the rise of drug-resistant malaria parasites, which is a serious health issue. Naringin (NGN), a flavanone glycoside (naringenin 7-O-neohesperidose), has a broad spectrum of pharmacological activities but its effect against malaria, alone and in combination, was not deeply investigated.

To assess the pharmacological efficacy of NGN alone and in combination with chloroquine (CQ) against a Plasmodium strain resistant to CQ and to elucidate its potential mode of action.

The anti-inflammatory potential of NGN was assessed in mouse microglial cells stimulated with hemozoin by analyzing inflammatory cytokines production. The anti-plasmodial potential of NGN was subsequently tested alone and in combination with CQ against the K1 strain of Plasmodium using the fixed ratio combination method. Further, we evaluated NGN's antimalarial efficacy against the CQ-resistant Plasmodium yoelii nigeriensis N67 strain (P. yoelii), both alone and in combination with CQ, by measuring parasitemia and survival rates. To comprehend the impact of NGN on malaria-induced inflammation in mice, we measured pro-inflammatory cytokines elevated by activated NF-кB signalling. These findings were supported by mRNA and immunohistochemical analyses of malaria-infected mice's liver and brain tissues.

Our study demonstrated that NGN displayed anti-plasmodial activity, which was further augmented when combined with CQ. At 50 µM, NGN significantly reduced the elevation of pro-inflammatory cytokines in synthetic hemozoin-stimulated microglial cells. Compared to P. yoelii-infected mice, NGN (12.5 mg kg^-1) significantly reduced parasitemia in mice, resulting in a survival period of up to 13 days. Survival improved by up to 20 days when NGN and CQ were given in combination. NGN, as revealed by immunohistochemical examination of brain and liver tissues, interfered with the NF-кB pathway, potentially reducing the elevation of pro-inflammatory cytokines (TNF-α, IL-1β, IL-18, IFN-γ, and IL-6). This was supported by the overexpression of inflammation-regulatory genes (TGFβ, Nrf2, HO-1, and iNOS) and the downregulation of inflammation-stimulating genes (NF-κB, NLRP3, and caspase-1). Histopathological analysis demonstrated the potential of NGN to restore liver and brain tissues to normal. The substantial decrease in the expression and production of ICAM-1 protein in the brain tissue implies the beneficial effects of NGN, pointing towards its potential for mitigating brain pathology.

The findings of this study revealed NGN as a promising drug-like candidate for the management of CQ-resistant parasite-induced malaria pathogenesis for adjunctive therapy in combination with standard antimalarial drugs through its modulation of the NF-κB-mediated inflammation.