Nuclear receptor activity ties to TB severity and offers a therapy target

Tuberculosis remains a disease where the body’s own responses help control the bacteria but can also be turned to the pathogen’s advantage. Researchers led by Margarida Saraiva looked for signals in patients and in laboratory models that might explain how the immune system’s metabolic shifts affect disease severity. They focused on nuclear receptors, a set of proteins that control how immune cells change their metabolism during infection. In particular, the team examined the signalling by nuclear receptors (SNR) pathway and a family of nuclear receptors called liver-X-receptors (LXR). Using blood samples from people with TB and lung samples from infected mice, the researchers asked whether activation of these pathways was associated with worse disease or provided a way to limit bacterial growth. Their work aimed to find markers that reflect how severe a person’s TB is and to test whether turning on specific nuclear receptor pathways could be used as a host-directed therapy that helps the body control Mycobacterium tuberculosis without directly targeting the bacteria with antibiotics.

The study detected the signalling by nuclear receptors (SNR) pathway in whole blood from TB patients and found that its expression correlated with disease severity. In mouse experiments, the researchers tracked the activation of liver-X-receptors (LXR) in the lungs of M. tuberculosis-infected C57BL/6 and C3HeB/FeJ mice and observed that LXR pathway activation increased progressively during infection. They then used pharmacologic activation of LXR, timed specifically at the chronic stage of infection. This treatment improved infection outcomes and significantly prolonged the survival of the highly susceptible C3HeB/FeJ mice. Across both mouse models and in in vitro macrophage infections, activating LXR enhanced bacterial control and was accompanied by an increase in extracellular cholesterol levels. These findings link the SNR and LXR pathways to measurable changes in infected tissues and cells and show that pharmacologic LXR activation can alter the course of chronic M. tuberculosis infection in experimental systems.

The work suggests two practical ideas. First, the signalling by nuclear receptors (SNR) pathway could serve as a biomarker in blood to indicate tuberculosis severity, offering a way to identify patients with more advanced or difficult-to-control disease. Second, timely activation of liver-X-receptors (LXR) appears to be a promising candidate for host-directed therapy: by adjusting host metabolism, in particular cholesterol handling, LXR activation may restrict a nutrient that M. tuberculosis uses and help the immune system contain the infection during chronic stages. The authors propose that progressive LXR activation fine-tunes host cholesterol availability and thereby limits bacterial access to this resource. Taken together, the results support further investigation of SNR pathway readouts in patients and carefully timed pharmacologic LXR activation as a complementary strategy to traditional antimicrobial treatments.