Isoegomaketone exhibits potential as a new Mycobacterium abscessus inhibitor.

Although the incidence of Mycobacterium abscessus infection has recently increased significantly, treatment is difficult because this bacterium is resistant to most anti-tuberculosis drugs. In particular, M. abscessus is often resistant to available macrolide antibiotics, so therapeutic options are extremely limited. Hence, there is a pressing demand to create effective drugs or therapeutic regimens for M. abscessus infections. The aim of the investigation was to assess the capability of isoegomaketone (iEMK) as a therapeutic option for treating M. abscessus infections. We determined the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of iEMK for both reference and clinically isolated M. abscessus strains. In addition to time-kill and biofilm formation assays, we evaluated iEMK's capability to inhibit M. abscessus growth in macrophages using an intracellular colony counting assay. iEMK inhibited the growth of reference and clinically isolated M. abscessus strains in macrophages and demonstrated effectiveness at lower concentrations against macrophage-infected M. abscessus than when used to treat the bacteria directly. Importantly, iEMK also exhibited anti-biofilm properties and the potential to mitigate macrolide-inducible resistance, underscoring its promise as a standalone or adjunctive therapeutic agent. Overall, our results suggest that further development of iEMK as a clinical drug candidate is promising for inhibiting M. abscessus growth, especially considering its dual action against both planktonic bacteria and biofilms.

Differential Immune Responses and Underlying Mechanisms of Metabolic Reprogramming in Smooth and Rough Variants of Mycobacterium peregrinum Infections.

Mycobacterium peregrinum (Mpgm) is a rapidly growing mycobacteria that is classified as a nontuberculous mycobacterium (NTM) and is commonly found in environmental sources such as soil, water, and animals. Mpgm is considered an opportunistic pathogen that causes infection in immunocompromised individuals or those with underlying medical conditions. Although there have been clinical reports on Mpgm, reports of the immune response and metabolic reprogramming have not been published. Thus, we studied standard Mpgm-ATCC and two clinical strains (Mpgm-S and Mpgm-R) using macrophages and mouse bone marrow-derived cells. Mpgm has two types of colony morphologies: smooth and rough. We grew all strains on the 7H10 agar medium to visually validate the morphology. Cytokine levels were measured via ELISA and real-time PCR. The changes in mitochondrial function and glycolysis in Mpgm-infected macrophages were measured using an extracellular flux analyzer. Mpgm-S-infected macrophages showed elevated levels of inflammatory cytokines, including interleukin (IL)-6, IL-12p40, and tumor necrosis factor (TNF)-α, compared to Mpgm-ATCC- and Mpgm-R-infected macrophages. Additionally, our findings revealed metabolic changes in Mpgm-ATCC and two clinical strains (Mpgm-S and Mpgm-R) during infection; significant changes were observed in the mitochondrial respiration, extracellular acidification, and the oxygen consumption of BMDMs upon Mpgm-S infection. In summary, within the strains examined, Mpgm-S displayed greater virulence, triggered a heightened immune response, and induced more profound shifts in bioenergetic metabolism than Mpgm-ATCC and Mpgm-R. This study is the first to document distinct immune responses and metabolic reorganization following Mpgm infection. These findings lay a crucial foundation for further investigations into the pathogenesis of Mpgm.

Aconitate Decarboxylase 1 Deficiency Exacerbates Mouse Colitis Induced by Dextran Sodium Sulfate.

Ulcerative colitis is a complex inflammatory bowel disorder disease that can induce rectal and colonic dysfunction. Although the prevalence of IBD in Western countries is almost 0.5% of the general population, genetic causes are still not fully understood. In a recent discovery, itaconate was found to function as an immune-modulating metabolite in mammalian immune cells, wherein it is synthesized as an antimicrobial compound from the citric acid cycle intermediate cis-aconitic acid. However, the association between the Acod1 (Aconitate decarboxylase 1)-itaconate axis and ulcerative colitis has rarely been studied. To elucidate this, we established a DSS-induced colitis model with Acod1-deficient mice and then measured the mouse body weights, colon lengths, histological changes, and cytokines/chemokines in the colon. We first confirmed the upregulation of Acod1 RNA and protein expression levels in DSS-induced colitis. Then, we found that colitis symptoms, including weight loss, the disease activity index, and colon shortening, were worsened by the depletion of Acod1. In addition, the extent of intestinal epithelial barrier breakdown, the extent of immune cell infiltration, and the expression of proinflammatory cytokines and chemokines in Acod1-deficient mice were higher than those in wild-type mice. Finally, we confirmed that 4-octyl itaconate (4-OI) alleviated DSS-induced colitis in Acod1-deficient mice and decreased the expression of inflammatory cytokines and chemokines. To our knowledge, this study is the first to elucidate the role of the Acod1-itaconate axis in colitis. Our data clearly showed that Acod1 deletion resulted in severe DSS-induced colitis and substantial increases in inflammatory cytokine and chemokine levels. Our results suggest that Acod1 may normally play an important regulatory role in the pathogenesis of colitis, demonstrating the potential for novel therapies using 4-OI.

Comparison of Macrophage Immune Responses and Metabolic Reprogramming in Smooth and Rough Variant Infections of Mycobacterium mucogenicum.

Mycobacterium mucogenicum (Mmuc), a rapidly growing nontuberculous mycobacterium (NTM), can infect humans (posttraumatic wound infections and catheter-related sepsis). Similar to other NTM species, Mmuc exhibits colony morphologies of rough (Mmuc-R) and smooth (Mmuc-S) types. Although there are several case reports on Mmuc infection, no experimental evidence supports that the R-type is more virulent. In addition, the immune response and metabolic reprogramming of Mmuc have not been studied on the basis of morphological characteristics. Thus, a standard ATCC Mmuc strain and two clinical strains were analyzed, and macrophages were generated from mouse bone marrow. Cytokines and cell death were measured by ELISA and FACS, respectively. Mitochondrial respiration and glycolytic changes were measured by XF seahorse. Higher numbers of intracellular bacteria were found in Mmuc-R-infected macrophages than in Mmuc-S-infected macrophages. Additionally, Mmuc-R induced higher levels of the cytokines TNF-α, IL-6, IL-12p40, and IL-10 and induced more BMDM necrotic death. Furthermore, our metabolic data showed marked glycolytic and respiratory differences between the control and each type of Mmuc infection, and changes in these parameters significantly promoted glucose metabolism, extracellular acidification, and oxygen consumption in BMDMs. In conclusion, at least in the strains we tested, Mmuc-R is more virulent, induces a stronger immune response, and shifts bioenergetic metabolism more extensively than the S-type. This study is the first to report differential immune responses and metabolic reprogramming after Mmuc infection and might provide a fundamental basis for additional studies on Mmuc pathogenesis.