Statins as Adjunctive Therapy Against Tuberculosis (TB): The Balance Between Statin-Induced Anti-TB Effect and Trained Immunity Suppression

The effect of statins on the risk of anti-tuberculosis drug-induced liver injury among patients with active tuberculosis: A cohort study

BACKGROUND

Tuberculosis (TB) remains prevalent worldwide, and anti-TB drugs are associated with drug-induced liver injury (DILI). Statins have pleiotropic effects which may decrease inflammation and achieve immunomodulation. However, few studies have investigated the pleiotropic effects of statins on the risk of DILI. The purpose of this study was to investigate whether statins prevent anti-tuberculosis DILI among active TB patients on standard anti-TB drug therapy.

METHODS

We conducted a hospital-based retrospective cohort study using claims data from the Integrated Medical Database of National Taiwan University Hospital (NTUH-iMD). Patients with a positive TB culture were included. The use of statins was defined as a daily equivalent dose >0.5 mg of pitavastatin. Deterioration in liver function was evaluated according to elevated liver enzyme levels. The primary and secondary endpoints were the DILI and the severe DILI. The prognostic value of statins was evaluated by Kaplan-Meier analysis, and Cox proportional hazards models.

RESULTS

A total of 1312 patients with a diagnosis of TB and receiving anti-TB treatment were included. During the study period, 193 patients had the DILI and 140 patients had the severe DILI. Kaplan-Meier analysis showed a significant difference between the usual statin users and controls in the DILI. In multivariable Cox proportional hazards analysis, statins showed a protective effect against the primary and secondary endpoints. In addition, the protective effect of statins showed a dose-response relationship against the DILI.

CONCLUSION

Statin treatment had a protective effect against the risk of anti-TB DILI with a positive dose-response relationship.

Further insights into to the role of statins against active tuberculosis: systematic review and meta-analysis

OBJECTIVES

Tuberculosis is a major cause of global morbidity and mortality. Statins could be associated with a lower risk of some infectious diseases, including tuberculosis. Statins could reduce the risk of latent tuberculosis infection and active tuberculosis, acting as an adjuvant in treating tuberculosis. This study aimed to determine if statins reduce the risk of active tuberculosis.

METHODS

We systematically analyzed 8 databases from inception to December 2021. We included articles without language restriction if they met our inclusion and exclusion criteria and the PECO strategy (Population: adults without active pulmonary tuberculosis; Exposure: treatment with any statin; Comparator: no use of statins; Outcome: active tuberculosis). Odds Ratios (ORs) with 95% confidence intervals (CIs) were pooled using random- effects models regardless of heterogeneity quantified by Cochran's Q and I² statistics. We performed subgroup analyses according to the participants' diabetic status and follow-up length (≤10 years or >10 years).

RESULTS

Twelve articles reporting observational studies involving 3.038.043 participants, including at least 32.668 cases of active tuberculosis. Eight reported retrospective cohort studies, three nested case-control study, and one was a case control study.According to our meta-analysis, statins may reduce the risk of active tuberculosis, in the general population (OR 0.66; 95% CI, 0.54-0.81), in non-diabetic (OR 0.66; 95% CI, 0.54-0.80) and in diabetic patients (OR 0.65; 95% CI, 0.49-0.87). This protective effect did not differ according to the participants' diabetic status nor follow-up length (test for subgroup differences I²=0). We found significant clinical and methodological heterogeneity. Similarly, the forest plot, and the I² and Chi² statistics suggested considerable statistical heterogeneity (I²=95%, p<0.05, respectively). Of the 12 included studies, 9 were at low risk of bias and 3 were at high risk of bias. Similarly, according to the funnel plot, it is very likely that there are important publication biases.

CONCLUSION

Statin use may significantly reduce the risk of tuberculosis in the general population, diabetic and non-diabetic patients. Nevertheless, caution should be exercised when interpreting these conclusions, due to the quality of the evidence, the heterogeneity of the studies, the presence of bias, and the difficulty in extrapolating these results to populations of other races and ethnicities.

Platelets mediate trained immunity against bone and joint infections in a mouse model

AIMS

Trained immunity confers non-specific protection against various types of infectious diseases, including bone and joint infection. Platelets are active participants in the immune response to pathogens and foreign substances, but their role in trained immunity remains elusive.

METHODS

We first trained the innate immune system of C57BL/6 mice via intravenous injection of two toll-like receptor agonists (zymosan and lipopolysaccharide). Two, four, and eight weeks later, we isolated platelets from immunity-trained and control mice, and then assessed whether immunity training altered platelet releasate. To better understand the role of immunity-trained platelets in bone and joint infection development, we transfused platelets from immunity-trained mice into naïve mice, and then challenged the recipient mice with Staphylococcus aureus or Escherichia coli.

RESULTS

After immunity training, the levels of pro-inflammatory cytokines (tumour necrosis factor alpha (TNF-α), interleukin (IL)-17A) and chemokines (CCL5, CXCL4, CXCL5, CXCL7, CXCL12) increased significantly in platelet releasate, while the levels of anti-inflammatory cytokines (IL-4, IL-13) decreased. Other platelet-secreted factors (e.g. platelet-derived growth factor (PDGF)-AA, PDGF-AB, PDGF-BB, cathepsin D, serotonin, and histamine) were statistically indistinguishable between the two groups. Transfusion of platelets from trained mice into naïve mice reduced infection risk and bacterial burden after local or systemic challenge with either S. aureus or E. coli.

CONCLUSION

Immunity training altered platelet releasate by increasing the levels of inflammatory cytokines/chemokines and decreasing the levels of anti-inflammatory cytokines. Transfusion of platelets from immunity-trained mice conferred protection against bone and joint infection, suggesting that alteration of platelet releasate might be an important mechanism underlying trained immunity and may have clinical implications. Cite this article: Bone Joint Res 2022;11(2):73-81.

The Prospect of Repurposing Immunomodulatory Drugs for Adjunctive Chemotherapy against Tuberculosis: A Critical Review

Tuberculosis (TB) remains a global health emergency, with an estimated 2 billion people infected across the world, and 1.4 million people dying to this disease every year. Many aspects of the causative agent, Mycobacterium tuberculosis, make this disease difficult for healthcare and laboratory researchers to fight against, such as unique pathophysiology, latent infection and long and complex treatment regimens, thus causing patient non-compliance with the treatment. Development of new drugs is critical for tackling these problems. Repurposing drugs is a promising strategy for generating an effective drug treatment whilst circumventing many of the challenges of conventional drug development. In this regard, the incorporation of immunomodulatory drugs into the standard regimen to potentiate frontline drugs is found to be highly appealing. Drugs of diverse chemical classes and drug categories are increasingly being evidenced to possess antitubercular activity, both in vitro and in vivo. This article explores and discusses the molecular entities that have shown promise in being repurposed for use in anti-TB adjunctive therapy and aims to provide the most up-to-date picture of their progress.

Does Training Innate Immunity Confer Broad-spectrum Protection Against Bone and Joint Infection in a Mouse Model?

BACKGROUND

The innate immune system can recall previous immunologic challenges and thus respond more effectively to subsequent unrelated challenges, a phenomenon called trained immunity. Training the innate immune system before surgery might be a potential option to prevent bone and joint infection.

QUESTIONS/PURPOSES

(1) Does the training process cause adverse effects such as fever or organ injury? (2) Does training the innate immune system confer broad-spectrum protection against bone and joint infection in a mouse model? (3) Does trained immunity remain effective for up to 8 weeks in this mouse model?

METHODS

After randomization and group information blinding, we trained the innate immune system of C57BL/6 mice (n = 20 for each group) by intravenously injecting them with either 0.1 mg of zymosan (a toll-like receptor 2 agonist), 0.1 mg of lipopolysaccharide (a toll-like receptor 4 agonist), or normal saline (control). For assessing the host response and possible organ injury after training and infection challenge, we monitored rectal temperature, collected blood to determine leukocyte counts, and performed biochemical and proinflammatory cytokine analyses. After 2 weeks, we then assessed whether trained immunity could prevent infections in an intraarticular implant model subjected to a local or systemic challenge with a broad spectrum of bacterial species (Staphylococcus aureus, Escherichia coli, Enterococcus faecalis, Streptococcus pyogenes, or Pseudomonas aeruginosa) in terms of culture-positive rate and colony counts. The proportion of culture-positive joint samples from trained and control groups were compared after 4 weeks. Finally, we increased the interval between training and bacterial challenge up to 8 weeks to assess the durability of training efficacies.

RESULTS

Training with zymosan and lipopolysaccharide caused mild and transient stress in host animals in terms of elevated rectal temperature and higher blood urea nitrogen, creatinine, alanine aminotransferase, and aspartate aminotransferase levels. Trained mice had fewer culture-positive joint samples after local inoculation with S. aureus (control: 100% [20 of 20]; zymosan: 55% [11 of 20], relative risk 0.55 [95% CI 0.37 to 0.82]; p = 0.001; lipopolysaccharide: 60% [12 of 20], RR 0.60 [95% CI 0.42 to 0.86]; p = 0.003) and systemic challenge with S. aureus (control: 70% [14 of 20]; zymosan: 15% [3 of 20], RR 0.21 [95% CI 0.07 to 0.63]; p = 0.001; lipopolysaccharide: 15% [3 of 20], RR 0.21 [95% CI 0.07 to 0.63]; p = 0.001) than controls. We observed similar patterns of enhanced protection against local and systemic challenge of E. coli, E. faecalis, S. pyogenes, and P. aeruginosa. Zymosan-trained mice were more effectively protected against both local (control: 20 of 20 [100%], zymosan: 14 of 20 [70%], RR 0.70 [95% CI 0.53 to 0.93]; p = 0.02) and systemic (control: 70% [14 of 20]; zymosan: 30% [6 of 20], RR 0.43 [95% CI 0.21 to 0.89]; p = 0.03) challenge with S. aureus for up to 8 weeks than controls.

CONCLUSIONS

Trained immunity confers mild stress and broad-spectrum protection against bone and joint infection in a mouse model. The protection conferred by immunity training lasted up to 8 weeks in this mouse model. The results of the current research support further study of this presurgical strategy to mitigate bone and joint infection in other large animal models.

CLINICAL RELEVANCE

If large animal models substantiate the efficacy and safety of presurgical immunity training-based strategies, clinical trials would be then warranted to translate this strategy into clinical practice.

Neutrophils in Tuberculosis-Associated Inflammation and Lung Pathology

Protective immunity to Mycobacterium tuberculosis (Mtb)—the causative agent of tuberculosis (TB)—is not fully understood but involves immune responses within the pulmonary airways which can lead to exacerbated inflammation and immune pathology. In humans, this inflammation results in lung damage; the extent of which depends on specific host pro-inflammatory processes. Neutrophils, though increasingly linked to the development of inflammatory disorders, have been less well studied in relation to TB-induced lung pathology. Neutrophils mode of action and their specialized functions can be directly linked to TB-specific lung tissue damage observed on patient chest X-rays at diagnosis and contribute to long-term pulmonary sequelae. This review discusses aspects of neutrophil activity associated with active TB, including the resulting inflammation and pulmonary impairment. It highlights the significance of neutrophil function on TB disease outcome and underlines the necessity of monitoring neutrophil function for better assessment of the immune response and severity of lung pathology associated with TB. Finally, we propose that some MMPs, ROS, MPO, S100A8/A9 and Glutathione are neutrophil-related inflammatory mediators with promising potential as targets for developing host-directed therapies for TB.