Corticosteroids protect infected cells against mycobacterial killing in vitro

Glucocorticoid alleviates hypothalamic nerve injury via remodeling HPA axis homeostasis in stressed rats

Excessive stress can exceed the adjustment ability of body and cause injury and dysfunction, while elucidation of the mechanism and prevention measures of stress-related injury are still insufficient. The present study was to observe the effect of glucocorticoid (GC) on stress-induced hypothalamic nerve injury and elucidate the potential mechanism. The present study intended to establish a chronic restraint stress rat model for follow-up study. Open field test and elevated plus maze test were used to observe behavioral changes of stress rats; Enzyme-linked immunosorbent assay (ELISA) was used to detect changes in the levels of hypothalamus-pituitary-adrenal (HPA) axis-related hormones and inflammatory factors in hypothalamus; toluidine blue staining was used to observe pathological changes of hypothalamus. The results showed that stress rats showed obvious anxiety-like behaviors, the levels of HPA axis-related hormones and inflammatory factors showed abnormal fluctuations, and morphological results showed significant nerve injury in hypothalamus. Low-dose GC treatment significantly improved behavioral changes, alleviated hypothalamic nerve injury, and restored hypothalamic levels of inflammatory factors, serum levels of GC, corticotropin-releasing hormone (CRH), and adrenocorticotropic hormone (ACTH) and GC level in adrenal cortex of stressed rats, while GC receptor (GR) inhibitor, CRH receptor inhibitor, and adrenalectomy reversed the ameliorative effects of low-dose GC. Our study clarified that low-dose GC can restore stress coping ability by reshaping the homeostasis of the HPA axis, thus alleviating behavioral abnormalities and hypothalamic nerve injury in stressed rats.

PDCD4 as a marker of mTOR pathway activation and therapeutic target in mycobacterial infections

Programmed cell death protein 4 (PDCD4) is instrumental in regulating a range of cellular processes such as translation, apoptosis, signal transduction, and inflammatory responses. There is a notable inverse correlation between PDCD4 and the mammalian target of rapamycin (mTOR) pathway, which is integral to cellular growth control. Activation of mTOR is associated with the degradation of PDCD4. Although the role of PDCD4 is well established in oncogenesis and immune response regulation, its function in mycobacterial infections and its interplay with the mTOR pathway necessitate further elucidation. This study investigates the modulation of PDCD4 expression in the context of mycobacterial infections, revealing a consistent pattern of downregulation across diverse mycobacterial species. This observation underscores the potential utility of PDCD4 as a biomarker for assessing mTOR pathway activation during such infections. Building on this finding, we employed a novel approach using PDCD4-based mTOR (Tor)-signal-indicator (TOSI) reporter cells for the high-throughput screening of FDA-approved drugs, focusing on mTOR inhibitors. This methodology facilitated the identification of several agents, inclusive of known mTOR inhibitors, which upregulated PDCD4 expression and concurrently exhibited efficacy in impeding mycobacterial proliferation within macrophages. These results not only reinforce the significance of PDCD4 as a pivotal marker in the understanding of infectious diseases, particularly mycobacterial infections, but also illuminate its potential in the identification of mTOR inhibitors, thereby contributing to the advancement of therapeutic strategies.

IMPORTANCE

This study emphasizes the critical role of the mammalian target of rapamycin (mTOR) pathway in macrophage responses to mycobacterial infections, elucidating how mycobacteria activate mTOR, resulting in PDCD4 degradation. The utilization of the (Tor)-signal-indicator (TOSI) vector for real-time monitoring of mTOR activity represents a significant advancement in understanding mTOR regulation during mycobacterial infection. These findings deepen our comprehension of mycobacteria's innate immune mechanisms and introduce PDCD4 as a novel marker for mTOR activity in infectious diseases. Importantly, this research laid the groundwork for high-throughput screening of mTOR inhibitors using FDA-approved drugs, offering the potential for repurposing treatments against mycobacterial infections. The identification of drugs that inhibit mTOR activation opens new avenues for host-directed therapies, marking a significant step forward in combating tuberculosis and other mycobacterial diseases.

Complicated Surgical Site Infection with Mycobacterium Abscessus After Liposuction and Affections of Corticosteroids in the Treatment Regimen: Three Cases Report and a Systematic Review

INTRODUCTION

Mycobacterium abscessus infection after liposuction/fat grafting is a rare complication that is hard to diagnose and treat. Misdiagnosis could result in treatment failure and prolonged hospital stays. The paradoxical reaction is another complication that rarely occurs in non-HIV patients infected with nontuberculosis mycobacteria. This study reported 3 cases infected with M. abscessus complicated by the paradoxical reaction after liposuction and fat grafting. It highlighted characteristics giving clues of the paradoxical reaction and a successful strategy. Also, a systematic review was conducted to comprehensively provide varied aspects of M. abscessus infection after liposuction and/or fat grafting.

METHODS

Three cases were retrospectively included reporting data characteristics of patients, cosmetic procedures, and treatment strategy. PubMed, Scopus, Virtual Health Library (VHL), and Global Health Library (GHL) were searched to find and include cases with M. abscessus infection after liposuction and/or fat grafting based on defined selection criteria. Relevant data were extracted and summarized. The risk of bias in included studies was assessed using JBI critical appraisal checklists.

RESULTS

Twenty-four articles were included in the systematic review. Symptoms often developed approximately 1 month after the cosmetic surgery. Culture, AFB, and PCR were common methods of diagnosis of M. abscessus after liposuction and/or fat grafting. It took about 33 days on average from the presentation to isolate and detect the pathogens. Antibiotics based on susceptibility testing results along with surgical interventions were effective methods of treatment. Our three cases which were complicated by the paradox were addressed by adding methylprednisolone for 2 weeks to the macrolide-based therapy.

CONCLUSIONS

Awareness of this disease should be widely raised among physicians for early diagnosis and proper treatments. Cultures of specimens and AFB should be repeated many times before excluding the possibility of Mycobacterium spp. A paradoxical reaction should be suspected if the symptoms were worse after the antibiotic therapy based on susceptibility testing results and proper surgical interventions, especially if patients had taken corticosteroids before being admitted.

LEVEL OF EVIDENCE III

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors   www.springer.com/00266 .

Effect of Low Doses of Dexamethasone on Experimental Pulmonary Tuberculosis

Tuberculosis (TB) is the deadliest disease caused by a bacterial agent. Glucocorticoids (GCs) have a typical anti-inflammatory effect, but recently it has been shown that they can present proinflammatory activity, mainly by increasing molecules from innate immunity. In the current study, we evaluated the effect of low doses of dexamethasone on Mycobacterium tuberculosis in vivo and in vitro. We used an established mice model of progressing tuberculosis (TB) in the in vivo studies. Intratracheal or intranasal dexamethasone therapy administered with conventional antibiotics in the late stage of the disease decreased the lung bacilli load and lung pneumonia, and increased the survival of the animals. Finally, the treatment decreased the inflammatory response in the SNC and, therefore, sickness behavior and neurological abnormalities in the infected animals. In the in vitro experiments, we used a cell line of murine alveolar macrophages infected with Mtb. Low-dose dexamethasone treatment increased the clearance capacity of Mtb by MHS macrophages, MIP-1α, and TLR2 expression, decreased proinflammatory and anti-inflammatory cytokines, and induced apoptosis, a molecular process that contributes to the control of the mycobacteria. In conclusion, the administration of low doses of dexamethasone represents a promising adjuvant treatment for pulmonary TB.

Morphology of Lymphoid Tissue in the Lungs of Guinea Pigs Infected with Mycobacterium bovis against the Background of Vaccine Immunity and the Action of Betulin and Its Derivatives

Tuberculosis caused by Mycobacterium bovis is a serious problem for animal and human health worldwide. A promising concept for the design of anti-tuberculosis drugs is the conjugation of an immunogenic fraction isolated from bacterial vaccines with a stimulating component. Taking this principle as a basis, conjugates based on BCG antigens with betulin and its derivatives (betulonic and betulinic acids) were designed. The aim of this research was to study the morphological changes in the lymphoid tissue associated with the bronchial mucosa lungs (BALT) in guinea pigs sensitized with experimental conjugates using a model of experimental tuberculosis. The results showed a significant decrease in the BALT response, expressed by a decrease in the diameter of lymphatic follicles and a decrease in their activity when exposed to conjugates based on BCG antigens with betulin and, especially, with betulonic acid, with a visually greater number of plasma cells observed in the lung tissues of guinea pigs of these groups. The absence of tuberculous foci and low BALT activity in the lungs of animals treated with betulin and betulonic acid are probably associated with the activation of humoral immunity under the action of these conjugates.

Metabolites enhance innate resistance to human Mycobacterium tuberculosis infection

To determine the mechanisms that mediate resistance to Mycobacterium tuberculosis (M. tuberculosis) infection in household contacts (HHCs) of patients with tuberculosis (TB), we followed 452 latent TB infection-negative (LTBI-) HHCs for 2 years. Those who remained LTBI- throughout the study were identified as nonconverters. At baseline, nonconverters had a higher percentage of CD14+ and CD3-CD56+CD27+CCR7+ memory-like natural killer (NK) cells. Using a whole-transcriptome and metabolomic approach, we identified deoxycorticosterone acetate as a metabolite with elevated concentrations in the plasma of nonconverters, and further studies showed that this metabolite enhanced glycolytic ATP flux in macrophages and restricted M. tuberculosis growth by enhancing antimicrobial peptide production through the expression of the surface receptor sialic acid binding Ig-like lectin-14. Another metabolite, 4-hydroxypyridine, from the plasma of nonconverters significantly enhanced the expansion of memory-like NK cells. Our findings demonstrate that increased levels of specific metabolites can regulate innate resistance against M. tuberculosis infection in HHCs of patients with TB who never develop LTBI or active TB.

α1-Antitrypsin Binds to the Glucocorticoid Receptor with Anti-Inflammatory and Antimycobacterial Significance in Macrophages

α1-Antitrypsin (AAT), a serine protease inhibitor, is the third most abundant protein in plasma. Although the best-known function of AAT is irreversible inhibition of elastase, AAT is an acute-phase reactant and is increasingly recognized to have a panoply of other functions, including as an anti-inflammatory mediator and a host-protective molecule against various pathogens. Although a canonical receptor for AAT has not been identified, AAT can be internalized into the cytoplasm and is known to affect gene regulation. Because AAT has anti-inflammatory properties, we examined whether AAT binds the cytoplasmic glucocorticoid receptor (GR) in human macrophages. We report the finding that AAT binds to GR using several approaches, including coimmunoprecipitation, mass spectrometry, and microscale thermophoresis. We also performed in silico molecular modeling and found that binding between AAT and GR has a plausible stereochemical basis. The significance of this interaction in macrophages is evinced by AAT inhibition of LPS-induced NF-κB activation and IL-8 production as well as AAT induction of angiopoietin-like 4 protein, which are, in part, dependent on GR. Furthermore, this AAT-GR interaction contributes to a host-protective role against mycobacteria in macrophages. In summary, this study identifies a new mechanism for the gene regulation, anti-inflammatory, and host-defense properties of AAT.

Low-cost anti-mycobacterial drug discovery using engineered E. coli

Whole-cell screening for Mycobacterium tuberculosis (Mtb) inhibitors is complicated by the pathogen's slow growth and biocontainment requirements. Here we present a synthetic biology framework for assaying Mtb drug targets in engineered E. coli. We construct Target Essential Surrogate E. coli (TESEC) in which an essential metabolic enzyme is deleted and replaced with an Mtb-derived functional analog, linking bacterial growth to the activity of the target enzyme. High throughput screening of a TESEC model for Mtb alanine racemase (Alr) revealed benazepril as a targeted inhibitor, a result validated in whole-cell Mtb. In vitro biochemical assays indicated a noncompetitive mechanism unlike that of clinical Alr inhibitors. We establish the scalability of TESEC for drug discovery by characterizing TESEC strains for four additional targets.

Review of the Effectiveness of Various Adjuvant Therapies in Treating Mycobacterium tuberculosis

Tuberculosis disease is caused by the bacterium Mycobacterium tuberculosis. It is estimated that 10 million people have developed tuberculosis disease globally, leading to 1.4 million deaths in 2019. Treatment of tuberculosis has been especially challenging due to the rise of multidrug-resistant (MDR-TB) and extensive drug-resistant (XDR-TB) tuberculosis. In addition to drug-resistant genotypes, the standard treatment of tuberculosis by first-line agents is also challenging due to toxicity and costs. In the last four decades, there have only been two new anti-tuberculosis agents—bedaquiline and delamanid. Therefore, shorter, safer, and more cost-effective therapies are needed to adequately treat tuberculosis. In this review, we explore various adjuvants such as glutathione, everolimus, vitamin D, steroid, aspirin, statin, and metformin and their usefulness in reducing the burden of tuberculosis. Glutathione, everolimus, aspirin, and metformin showed the most promise in alleviating the burden of tuberculosis. Despite their potential, more clinical trials are needed to unequivocally establish the effectiveness of these adjuvants as future clinical therapies. Methods: The journals for this review were selected by conducting a search via PubMed, Google Scholar, and The Lancet. Our first search included keywords such as “tuberculosis” and “adjuvant therapy.” From the search, we made a list of adjuvants associated with tuberculosis, and this helped guide us with our second online database search. Using the same three online databases, we searched “tuberculosis” and “respective therapy.” The adjuvants included in the paper were selected based on the availability of sufficient research and support between the therapy and tuberculosis. Adjuvants with minimal research support were excluded. There were no specific search criteria regarding the timing of publication, with our citations ranging between 1979 to 2021.