Vitamin D enhances IL-1 beta secretion and restricts growth of Mycobacterium tuberculosis in macrophages from TB patients

The emergence of multidrug-resistant strains of Mycobacterium tuberculosis [MTB], the bacterium responsible for tuberculosis [TB], has rekindled the interest in the role of nutritional supplementation of micronutrients, such as vitamin D, as adjuvant treatment. Here, the growth of virulent MTB in macrophages obtained from the peripheral blood of patients with and without TB was studied. The H37Rv strain genetically modified to express Vibrio harveyi luciferase was used to determine the growth of MTB by luminometry in the human monocyte-derived macrophages [hMDMs] from study subjects. Determination of cytokine levels in culture supernatants was performed using a flow cytometry-based bead array technique. No differences in intracellular growth of MTB were observed between the different study groups. However, stimulation with 100 nM 1,25-dihydroxyvitamin D significantly enhanced the capacity of hMDMs isolated from TB patients to control the infection. This effect was not observed in hMDMs from the other groups. The interleukin [IL]-1 beta and IL-10 release by hMDMs was clearly increased upon stimulation with 1,25-dihydroxyvitamin D. Furthermore, the 1,25-dihydroxyvitamin D stimulation also led to elevated levels of TNF-alpha [tumor necrosis factor-alpha] and IL-12p40. It was concluded that vitamin D triggers an inflammatory response in human macrophages with enhanced secretion of cytokines, as well as enhancing the capacity of hMDMs from patients with active TB to restrict mycobacterial growth

Tentative susceptibility testing breakpoint for the neuroleptic drug thioridazine, a treatment option for multiband extensively drug resistant tuberculosis

New drugs against multi-[MDR] and extensively drug [XDR] resistant tuberculosis are urgently needed. While new candidate drugs are being developed, reinvestigation of already approved drugs available for other indications could be of value. The objective of this study is to determine tentative drug susceptibility testing strategies and breakpoints for thioridazine, a well-known and well-tolerated neuroleptic drug, which has been shown to be effective against drug resistant tuberculosis both in vitro and in vivo. By testing the minimal inhibitory concentration [MIC] on Middlebrook 7H10 media, the wild-type distribution of thioridazine was established for Mycobacterium tuberculosis [n = 51] and this distribution was compared to the MICs of M/XDR strains [n = 67]. A tentative epidemiological cut off [ECOFF] of thioridazine at 16 mg/L was suggested. Even though such concentrations are not clinically achievable in serum, thioridazine is concentrated intracellularly and concentrations of only 0.1 mg/L has been shown to kill M. tuberculosis residing inside cells. MICs above the wild-type [MIC > 16 mg/L] were found in 4/67 [6%] of the M/XDR strains suggesting that resistance mechanisms against thioridazine may already be present in resistant clinical strains. In view of the difficulties obtaining clinical outcome data for single drugs in the case of tuberculosis since combination therapy is mandatory, the tentative ECOFF may be considered a tentative clinical breakpoint, but the findings should be validated by others. The data from this study strengthens the use of thioridazine as a treatment option for M/XDR tuberculosis, although its proper place in the therapeutic arsenal should ideally be confirmed in clinical trials.