In Vivo Anti-Inflammatory Activity, Safety and Effect on Gene Expression Profiles of Selected Medicinal Plants against Rheumatoid Arthritis in a Mouse Model

Abstract

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease. Current RA treatments aim to alleviate symptoms, slow disease progression, and improve quality of life. However, these treatments are often associated with adverse side effects. Consequently, traditional herbal remedies are being investigated as potential alternatives due to their perceived lower toxicity and suitability for long-term use. This study evaluated the safety and efficacy of aqueous and organic extracts from Carissa edulis, Withania somnifera, Prunus africana, and Rhamnus prinoides in managing RA, a practice prevalent in Kenyan local communities. Inflammation was induced in Mice with Lambda IV Carrageenan and the anti-inflammatory activity was determined by calculating the percentage inhibition. Gene expression of IL-6, TNF-α, and IL-4 was quantified using Real-Time Polymerase Chain Reaction. Acute oral and sub-acute toxicity were assessed in Swiss albino mice, and phytochemical constituents were analyzed qualitatively. Acute toxicity studies showed no mortality or significant changes in body weight and behavioral parameters at a 2000 mg/kg dose. Sub-acute toxicity confirmed the absence of toxic effects, as evidenced by stable weekly body weights compared to the untreated group (P≥0.05). Both aqueous and organic extracts exhibited dose-dependent anti-inflammatory activity. At 50 mg/kg, the percentage inhibition for aqueous extracts ranged from 42.19% to 45.59%, while organic extracts demonstrated higher inhibition, ranging from 44.53% to 55.60%. At 100 mg/kg, organic extracts showed consistently higher inhibition, with W. somnifera and R. prinoides exhibiting the highest values (58.23% and 58.13%, respectively). Gene expression analysis revealed that organic extracts significantly downregulated pro-inflammatory cytokines IL-6 and TNF-α. At 100 mg/kg, W. somnifera and C. edulis showed the lowest relative fold changes for IL-6 (0.16) and TNF-α (0.13), respectively, indicating potent suppression. All extracts also upregulated the anti-inflammatory cytokine IL-4. Aqueous extracts also downregulated IL-6 and TNF-α, albeit to a lesser extent than organic extracts, and upregulated IL-4 (P≤0.05). These findings suggest that extracts from C. edulis, W. somnifera, P. africana, and R. prinoides, particularly the organic extracts, possess significant anti-inflammatory and immunomodulatory properties, supporting their potential application in RA management and as leads for novel RA drug development