Immunomodulatory effect of Premna odorata volatile oils in Mycobacterium tuberculosis by inhibiting TLR4/NF-κB pathway

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Introduction: The development of multi drug resistant (MDR) tuberculosis (TB) and extensively drug resistant (XDR) TB, increased the interest in the usage of medicinal plants that are complementary to antibiotics to improve anti-TB efficacy. The present study aimed to confirm the anti-TB efficacy of volatile oils (VOs) isolated from different parts of Premna odorata in vivo, and moreover, to test the possible involvement of TLR4/NF-κB signaling pathway in its anti-TB efficacy. Methods: Thirty mice were divided into six equal groups. Group 1: healthy mice (negative control). Groups 2-6 were injected intravenously with a positive TB solution of purified MeDiPro Mycobacterium tuberculosis (MTB) antigen for 7 days to induce tuberculosis. Group 3-6: TB-injected mice treated respectively with leaves VO (300 μL/d), young stems VO (300 μL/d), flowers VO and a combination of the three essential VOs (1:1:1). Various immunologic factors and antioxidant activity were evaluated and compared in the groups. Results: TB-infected mice showed a significant increase in the serum levels of tumor necrosis factor-α (TNF-α), interferon-gamma (IFN-γ), interleukin (IL) 1-β and the mRNA expression levels of toll-like receptor 4 (TLR-4) & nuclear factor-κB (NF-κB) and a decrease in IL-10 & total antioxidant capacity (TAC). While pretreatment with VOs extracted from leaves, flowers, young stems and a combination of the three oils reversed these effects. Conclusion: The immunomodulatory effects of VOs extracted from different parts of P. odorata against TB infection involve the TLR-4/NFκB signaling pathway as well as, antioxidant effects, recommending that the use of this plant may help TB infected patients.