RESUMO
The treatment for tuberculosis (TB), especially multidrug-resistant TB (MDR-TB), has a prolonged cycle which can last up to a year. This is partially due to the lack of effective therapies. The development of novel anti-TB drugs from the perspective of host immune regulation can provide an important supplement for conventional treatment strategies. Salidroside (SAL), a bioactive component from the Tibetan medicine Rhodiola rosea, has been used in the treatment of TB, although its mechanism remains unclear. Here, the bacteriostatic effect of SAL in vivo was first demonstrated using a zebrafish-M. marinum infection model. To further investigate the underlying mechanism, we then examined the impact of SAL on immune cell recruitment during wound and infection. Increased macrophage and neutrophil infiltrations were found both in the vicinity of the wound and infection sites after SAL treatment compared with control, which might be due to the elevated chemokine expression levels after SAL treatment. SAL treatment alone was also demonstrated to improve the survival of infected zebrafish larvae, an effect that was amplified when combining SAL treatment with isoniazid or rifampicin. Interestingly, the reduced bacterial burden and improved survival rate under SAL treatment were compromised in tnfα-deficient embryos which suggests a requirement of Tnfα signaling on the anti-mycobacterial effects of SAL. In summary, this study provides not only the cellular and molecular mechanisms for the host anti-mycobacterial effects of the Tibetan medicine SAL but also proof of concept that combined application of SAL with traditional first-line anti-TB drugs could be a novel strategy to improve treatment efficacy.
RESUMO
BACKGROUND: A defined Microbial Ecosystem Therapeutic (MET-1, or "RePOOPulate") derived from the feces of a healthy volunteer can cure recurrent C. difficile infection (rCDI) in humans. The mechanisms of action whereby healthy microbiota protect against rCDI remain unclear. Since C. difficile toxins are largely responsible for the disease pathology of CDI, we hypothesized that MET-1 exerts its protective effects by inhibiting the effects of these toxins on the host. METHODS: A combination of in vivo (antibiotic-associated mouse model of C. difficile colitis, mouse ileal loop model) and in vitro models (FITC-phalloidin staining, F actin Western blots and apoptosis assay in Caco2 cells, transepithelial electrical resistance measurements in T84 cells) were employed. RESULTS: MET-1 decreased both local and systemic inflammation in infection and decreased both the cytotoxicity and the amount of TcdA detected in stool, without an effect on C. difficile viability. MET-1 protected against TcdA-mediated damage in a murine ileal loop model. MET-1 protected the integrity of the cytoskeleton in cells treated with purified TcdA, as indicated by FITC-phalloidin staining, F:G actin assays and preservation of transepithelial electrical resistance. Finally, co-incubation of MET-1 with purified TcdA resulted in decreased detectable TcdA by Western blot analysis. CONCLUSIONS: MET-1 intestinal microbiota confers protection against C. difficile and decreases C. difficile-mediated inflammation through its protective effects against C. difficile toxins, including enhancement of host barrier function and degradation of TcdA. The effect of MET-1 on C. difficile viability seems to offer little, if any, contribution to its protective effects on the host.