The role of the PI3K/mTOR signaling pathway in Staphylococcus epidermidis small colony variants intracellular survival

Autophagy-related signaling pathways in non-small cell lung cancer

Lung cancer is one of the most prevalent causes of morbidity and mortality in both men and women across the globe. The disease has a quiet phenotype at first, which leads to chronic tumor development. Non-small cell lung cancer (NSCLC) is the most common kind of lung cancer, accounting for 85 percent of all lung malignancies. Autophagy has been described as an intracellular "recycle bin" where damaged proteins and molecules are degraded. Autophagy regulation is mainly dependent on signaling pathways such as phosphoinositide 3-kinases (PI3K), AKT, and the mammalian target of rapamycin (mTOR). In the context of NSCLC, studies on these signaling pathways are inconsistent, but our literature review suggests that the inhibition of mTOR, PI3K/AKT, and epidermal growth factor receptor signaling pathways by different medications can active autophagy and inhibit NSCLC progression. In conclusion, signaling pathways related to autophagy are effective therapeutic approaches for the treatment of NSCLC.

MicroRNA hsa-let-7a facilitates staphylococcal small colony variants survival in the THP-1 macrophages by reshaping inflammatory responses

Recent studies have provided emerging evidence of the critical involvement of microRNAs in host immune defence against bacterial infection and that likewise the expression of the miRNAs is profoundly impacted by a variety of pathogens to subvert the immune response. Here, we report the role of hsa-let-7a miRNA in response to Staphylococcus epidermidis Small Colony Variants infection. We also assessed whether the expression levels of inflammatory cytokines associated with the hsa-let-7a are manipulated by the pathogen and the effect of the IFN-γ priming on the expression of hsa-let-7a and the fate of SCVs/WTs in infected macrophages. A striking observation was the downregulation of the let-7a miRNA upon challenge of the THP-1 activated cells with the SCV isolates while no significant changes in expression were noticed after the infection of macrophages with their WT counterparts. Staphylococcus epidermidis WT and SCV strains were found to invade and survive in macrophages. A significant reduction in bacterial load for both phenotypes was observed in macrophages treated with let-7a mimic compared to untreated ones. Survival of WTs was augmented in cells treated with the inhibitor in 4 out of 5 strains as compared to the number of bacteria recovered from non-transfected cells. At the same time, let-7a inhibitor did not influence on the survival of SCVs in macrophages as their number was comparable to number recovered from non-transfected cells. When the ratio of both let-7a cytokine targets was compared, anti-inflammatory IL-10 cytokine was induced by SCVs predominantly, while the macrophage challenge with WTs was characterized by the inflammatory cytokine profile with high IL-6 and low IL-10 production. Moreover, the balance between pro-inflammatory and anti-inflammatory cytokines has been expectedly retrieved when macrophages were transfected with let-7a mimic before infection with WT or SCV strains. The results also show that IFN-γ likely regulates the macrophage environment contributing to the inflammatory response and elimination of bacteria from intracellular milieu by augmenting the synthesis of pro-inflammatory cytokines and supressing the anti-inflammatory IL-10. Our work has shown that SCVs have the potential to regulate the let-7a miRNA to balance the pro-inflammatory IL-6 with anti-inflammatory IL-10 and this mechanism is one of the ways in a complex regulatory network adopted by SCVs to promote their survival.

The roles, controversies, and combination therapies of autophagy in lung cancer

Lung cancer is one of the leading causes of death among men and women worldwide. The disease initially has a silent phenotype, which leads to the progression of the disease and ultimately the lack of proper response to routine treatments. Autophagy, known as an intracellular "recycle bin" for the degradation of defective proteins and molecules, is one of the mechanisms that has been considered in the context of cancer in recent years. This study aims to provide a comprehensive review of published articles on autophagy in the context of lung cancer to have a complete view of the role of autophagy in lung cancer and its possible treatments. PubMed, Scopus, and Google Scholar were searched until June 15 to find related articles. No specific search filters or restrictions were applied. The results were entered into reference management software for aggregation and management. The full text of all articles was screened and studied. In conclusion, studies on the exact function of autophagy in lung cancer are contradictory, but what can be concluded from a review of literature on lung cancer is that targeting autophagy combined with traditional routine therapies such as chemotherapy, especially in advanced stages of lung cancer, can be an effective anticancer approach.

The road to success of coagulase-negative staphylococci: clinical significance of small colony variants and their pathogenic role in persistent infections

Bacterial small colony variants represent an important aspect of bacterial variability. They are naturally occurring microbial subpopulations with distinctive phenotypic and pathogenic traits, reported for many clinically important bacteria. In clinical terms, SCVs tend to be associated with persistence in host cells and tissues and are less susceptible to antibiotics than their wild-type (WT) counterparts. The increased tendency of SCVs to reside intracellularly where they are protected against the host immune responses and antimicrobial drugs is one of the crucial aspects linking SCVs to recurrent or chronic infections, which are difficult to treat. An important aspect of the SCV ability to persist in the host is the quiescent metabolic state, reduced immune response and expression a changed pattern of virulence factors, including a reduced expression of exotoxins and an increased expression of adhesins facilitating host cell uptake. The purpose of this review is to describe in greater detail the currently available data regarding CoNS SCV and, in particular, their clinical significance and possible mechanisms by which SCVs contribute to the pathogenesis of the chronic infections. It should be emphasized that in spite of an increasing clinical significance of this group of staphylococci, the number of studies unraveling the mechanisms of CoNS SCVs formation and their impact on the course of the infectious process is still scarce, lagging behind the studies on S. aureus SCVs.

Berberine Attenuates Cardiac Hypertrophy Through Inhibition of mTOR Signaling Pathway

PURPOSE

Berberine was reported to exert beneficial effects on cardiac hypertrophy. However, its cellular and molecular mechanisms still remained unclear.

METHODS

Cardiac hypertrophy was induced in male Sprague-Dawley (SD) rats by transverse aorta constriction (TAC), with or without 6-week treatment of berberine. Echocardiography was performed to evaluate cardiac function. Rats were then sacrificed for histological assay, with detection for proteins and mRNA. H9c2 cells were pretreated with berberine of different concentrations (0, 1 μM, and 10 μM), followed by treatment with 2 μM norepinephrine (NE). Cells of different groups were measured for cell surface area, with mRNA detected by qRT-PCR and proteins by western blot.

RESULTS

Compared with the sham group, rats of the TAC group showed significantly increased cardiac hypertrophy and fibrosis, which could be ameliorated by treatment with berberine. Western blot showed that mammalian target of rapamycin (mTOR) signaling-related protein expressions, including phospho-mTOR, phospho-4EBP1, and phospho-p70 S6K (Thr389), but not phospho-p70 S6K (Ser371), were significantly increased in the TAC group, which were inhibited by berberine treatment. H9c2 cells were treated with NE to induce hypertrophy with increased cell surface area and mRNA expressions of anp and bnp. Berberine of 10 μM, but not 1 μM, significantly ameliorated NE-induced hypertrophy and inhibited protein expressions of mTOR signaling pathway similar to those in the rat model.

CONCLUSIONS

Berberine can exert cardioprotective effects on both pressure-overloaded cardiac hypertrophy and failure in vivo and NE-induced hypertrophy in vitro. Our results suggest berberine could be a potential treatment for patients with cardiac hypertrophy and failure.

The central role of the SOS DNA repair system in antibiotics resistance: A new target for a new infectious treatment strategy

Bacteria have a considerable ability and potential to acquire resistance against antimicrobial agents by acting diverse mechanisms such as target modification or overexpression, multidrug transporter systems, and acquisition of drug hydrolyzing enzymes. Studying the mechanisms of bacterial cell physiology is mandatory for the development of novel strategies to control the antimicrobial resistance phenomenon, as well as for the control of infections in clinics. The SOS response is a cellular DNA repair mechanism that has an essential role in the bacterial biologic process involved in resistance to antibiotics. The activation of the SOS network increases the resistance and tolerance of bacteria to stress and, as a consequence, to antimicrobial agents. Therefore, SOS can be an applicable target for the discovery of new antimicrobial drugs. In the present review, we focus on the central role of SOS response in bacterial resistance mechanisms and its potential as a new target for control of resistant pathogens.

The Controversial Role of Autophagy in Tumor Development: A Systematic Review

Autophagy is a natural regulatory mechanism of the cell that eliminates unnecessary and dysfunctional cellular components to maintain homeostasis. Several authors have demonstrated that this mechanism can be induced by pathological conditions as cancer. However, their role in tumor development is still a controversial issue in cancer research. Here, we discussed the most relevant findings concerning autophagy in tumor development. In this critical review performed with studies published between 2002 and 2018, we found that the main pathway involved in the autophagy process is the PI3K/AKT/mTOR intracellular signaling pathway. Regarding their role in cancer development, breast cancer is the main study target, followed by lung, prostate and colon cancer. In these issues, 46% of the works consulted suggesting that autophagy inhibits tumor progression by favor a better antitumor response, 4% suggest that favors growth and tumor progression and, 50% of the authors failed to establish whether autophagy inhibits or favors tumor development. Herein, we concluded that depending on the study model, autophagy may favor or inhibits growth and cancer progression.

Intraphagolysosomal conditions predispose to Staphylococcus epidermidis small colony variants persistence in macrophages

Staphylococcus epidermidis small colony variants can survive inside macrophages and their survival has been proposed as a pivotal process in the pathogenesis of biomaterial associated infections. In the present study the intracellular location of clinical isolates of SCV and parental wild type strains inside macrophages was determined. Furthermore, the effect of IFN-γ and rapamycin on the level of SCV/WT as well as lysosomes colocalisation and iNOS induction in THP-activated macrophages in response to WT and SCV strains of Staphylococcus epidermidis were examined. It was demonstrated that SCV strain of S. epidermidis can survive and persist inside macrophages and its intracellular survival is supported by the induction of phagosomal acidification. The ability to reduce the high proportion of LysoTracker positive SCV containing phagosomes was exclusively found when IFN-γ was used. The findings suggest that IFN-γ mediates SCV killing via two distinct mechanisms, phagosome alkalisation and an increased iNOS synthesis, so the cytokine may control S. epidermidis WT and SCV infection in macrophages. Staphylococcus epidermidis SCV is a less potent stimulus of iNOS than the WT strain and the feature may help SCV to persist in hostile environment of macrophages. Rapamycin treatment did not influence the iNOS synthesis but reduced the percentage of both bacterial strains within acidic organelles. However, the percentage of SCV within LysoTracker positive organelles, even though reduced comparing to non-primed cells, was higher than in the WT strain indicating that Staphylococcus epidermidis possesses unique metabolic features allowing SCV to survive within macrophages.

Survival of Staphylococcus epidermidis in Fibroblasts and Osteoblasts

Staphylococcus epidermidis is a leading cause of infections associated with indwelling medical devices, including prosthetic joint infection. While biofilm formation is assumed to be the main mechanism underlying the chronic infections S. epidermidis causes, we hypothesized that S. epidermidis also evades immune killing, contributing to its pathogenesis. Here, we show that prosthetic joint-associated S. epidermidis isolates can persist intracellularly within human fibroblasts and inside human and mouse osteoblasts. We also show that the intracellularly persisting bacteria reside primarily within acidic phagolysosomes and that over the course of infection, small-colony variants are selected for. Moreover, upon eukaryotic cell death, these bacteria, which can outlive their host, can escape into the extracellular environment, providing them an opportunity to form biofilms on implant surfaces at delayed time points in implant-associated infection. In summary, the acidic phagolysosomes of fibroblasts and osteoblasts serve as reservoirs for chronic or delayed S. epidermidis infection.