Autophagy gene ATG5 knockdown upregulates apoptotic cell death during Candida albicans infection in human vaginal epithelial cells

Autophagy and LC3-associated phagocytosis contribute negatively to the killing capability of THP-1-derived macrophages against Candida albicans at the mid-stage

In innate immunity, macrophages play critical roles in defending against pathogens via the lysosomal degradation function of autophagy. Two distinct autophagy pathways have been identified in decades: canonical autophagy (referred to as autophagy) and LC3-associated phagocytosis (LAP). Since several conflicting findings about the anti-Candida capability of autophagy (or LAP) have been reported, they serve as the foe or friend for Candida survival is still unclearly. The current study showed that the fungicidal process of THP-1-derived macrophages (THP-1-MФ) against Candida albicans is divided into three stages as follows, the early stage (the first 12 h, increasing in the killing capability), the mid-stage (12-24 h, no change in killing capability), and the late stage (24-48 h, decreasing of the killing capability). Autophagic protein LC3B-II reached the peak in THP-1-MФ after 24 h inoculated either with C.albicans or whole glucan particles (WGP). Thus, both anti-Candida roles of autophagy and the LAP pathway have been detected at the mid-stage. For autophagy, after 24 h inoculation with C.albicans, ULK1 increased, but p-ATG13(s318) decreased obviously in THP-1-MФ, and the killing assay showed that autophagy is unhelpful for Candida killing capability. For the LAP pathway, Rubicon and ROS raised significantly in THP-1-MФ after 24 h inoculated with C.albicans; each inhibition would sharply cut down the LC3B-II accumulation, which indicated that LAP had been induced. However, mCherry-GFP-LC3 fluorescent assay exhibited that LAP phago-lysosomal fusion has been blocked, and Rubicon knockdown facilitated the Candida killing activity. These data indicated that autophagy presented as redundant to Candida defense, and LAP phago-lysosomal fusion obstruction impairs the Candida killing capability of THP-1-MФ at the mid-stage. That may explain the no change in Candida killing capability at the mid-stage.

Autophagy-mediated immune system regulation in reproductive system and pregnancy-associated complications

Autophagy lysosomal degradation is the main cell mechanism in cellular, tissue and organismal homeostasis and is controlled by autophagy-related genes (ATG). Autophagy has important effects in cellular physiology, including adaptation to metabolic stress, removal of dangerous cargo (such as protein aggregates, damaged organelles, and intracellular pathogens), regeneration during differentiation and development, and prevention of genomic damage in general. Also, it has been found that autophagy is essential for pre-implantation, development, and maintaining embryo survival in mammals. Under certain conditions, autophagy may be detrimental through pro-survival effects such as cancer progression or through possible cell death-promoting effects. Hormonal changes and environmental stress can initiate autophagy in reproductive physiology. The activity of autophagy can be upregulated under conditions like a lack of nutrients, inflammation, hypoxia, and infections. In this regard the dysregulation of autophagy involved in some pregnancy complications such as preeclampsia (PE) and pregnancy loss, and has a major impact on reproductive outcomes. Therefore, we aimed to discuss the relationship between autophagy and the female reproductive system, with a special focus on the immune system, and its role in fetal and maternal health.

The roles of autophagy and mitophagy in corneal pathology: current knowledge and future perspectives

The cornea is the clear dome that covers the front portion of the globe. The primary functions of the cornea are to promote the refraction of light and to protect the eye from invading pathogens, both of which are essential for the preservation of vision. Homeostasis of each cellular layer of the cornea requires the orchestration of multiple processes, including the ability to respond to stress. One mechanism whereby cells respond to stress is autophagy, or the process of "self-eating." Autophagy functions to clear damaged proteins and organelles. During nutrient deprivation, amino acids released from protein breakdown via autophagy are used as a fuel source. Mitophagy, a selective form of autophagy, functions to clear damaged mitochondria. Thus, autophagy and mitophagy are important intracellular degradative processes that sustain tissue homeostasis. Importantly, the inhibition or excessive activation of these processes result in deleterious effects on the cell. In the eye, impairment or inhibition of these mechanisms have been associated with corneal disease, degenerations, and dystrophies. This review summarizes the current body of knowledge on autophagy and mitophagy at all layers in the cornea in both non-infectious and infectious corneal disease, dystrophies, and degenerations. It further highlights the critical gaps in our understanding of mitochondrial dysfunction, with implications for novel therapeutics in clinical practice.

Autophagy and Skin Diseases

Autophagy is a highly conserved lysosomal degradation system that involves the creation of autophagosomes, which eventually fuse with lysosomes and breakdown misfolded proteins and damaged organelles with their enzymes. Autophagy is widely known for its function in cellular homeostasis under physiological and pathological settings. Defects in autophagy have been implicated in the pathophysiology of a variety of human diseases. The new line of evidence suggests that autophagy is inextricably linked to skin disorders. This review summarizes the principles behind autophagy and highlights current findings of autophagy's role in skin disorders and strategies for therapeutic modulation.

Membrane protective role of autophagic machinery during infection of epithelial cells by Candida albicans

Candida albicans (C. albicans) is an opportunistic pathogen causing infections ranging from superficial to life-threatening disseminated infections. In a susceptible host, C. albicans is able to translocate through the gut barrier, promoting its dissemination into deeper organs. C. albicans hyphae can invade human epithelial cells by two well-documented mechanisms: epithelial-driven endocytosis and C. albicans-driven active penetration. One mechanism by which host cells protect themselves against intracellular C. albicans is termed autophagy. The protective role of autophagy during C. albicans infection has been investigated in myeloid cells; however, far less is known regarding the role of this process during the infection of epithelial cells. In the present study, we investigated the role of autophagy-related proteins during the infection of epithelial cells, including intestinal epithelial cells and gut explants, by C. albicans. Using cell imaging, we show that key molecular players of the autophagy machinery (LC3-II, PI3P, ATG16L1, and WIPI2) were recruited at Candida invasion sites. We deepened these observations by electron microscopy analyses that reveal the presence of autophagosomes in the vicinity of invading hyphae. Importantly, these events occur during active penetration of C. albicans into host cells and are associated with plasma membrane damage. In this context, we show that the autophagy-related key proteins ATG5 and ATG16L1 contribute to plasma membrane repair mediated by lysosomal exocytosis and participate in protecting epithelial cells against C. albicans-induced cell death. Our findings provide a novel mechanism by which epithelial cells, forming the first line of defense against C. albicans in the gut, can react to limit C. albicans invasion.

Ethyl Extract of Blaps rynchopetera Fairmaire Ameliorates Experimental Aerobic Vaginitis by Inhibiting Autophagy Activation

To investigate the therapeutic effects of Blaps rynchopetera Fairmaire (BRF) extracts on the autophagy activation in a rat model of aerobic vaginitis (AV), forty-eight adult female SD rats of the AV model were divided into five groups according to different treatments with the cream matrix, antibiotics (clindamycin phosphate, 20 mg/g), low-concentration extracts (100 mg/g), medium-concentration extracts (200 mg/g), or high-concentration extracts (300 mg/g). Two weeks after treatment, we conducted a series of assays, including measuring the improved Donders score and pH value of vaginal secretions, H&E staining, immunohistochemical (IHC) staining, western blotting, and ELISA, for evaluating the protein expression of autophagy biomarkers Beclin1 and LC3B. In vitro, BRF ethyl extracts had the lowest minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). After administration in AV rats, the improved Donders score, pH value, and vaginal histopathology score of vaginal secretions in the model and low-concentration groups were not statistically different from those in the normal group. In contrast, these indicators improved significantly in other treatment groups, especially in the high-concentration group. Additionally, when compared to the normal group, IHC, western blot, and ELISA revealed no statistically significant difference in the expressions of Beclin1 and LC3B in the model and low-concentration groups, but decreased to varying degrees in the clindamycin, medium-concentration, and high-concentration groups, with no correlation between Beclin1 and LC3B. Medium- and high-concentration BRF ethyl extracts effectively treated AV in rats by inhibiting excessive autophagy activation and could be applied in the clinic future.

In vitro infection models to study fungal-host interactions

Fungal infections (mycoses) affect over a billion people per year. Approximately, two million of these infections are life-threatening, especially for patients with a compromised immune system. Fungi of the genera Aspergillus, Candida, Histoplasma and Cryptococcus are opportunistic pathogens that contribute to a substantial number of mycoses. To optimize the diagnosis and treatment of mycoses, we need to understand the complex fungal-host interplay during pathogenesis, the fungal attributes causing virulence and how the host resists infection via immunological defenses. In vitro models can be used to mimic fungal infections of various tissues and organs and the corresponding immune responses at near-physiological conditions. Furthermore, models can include fungal interactions with the host-microbiota to mimic the in vivo situation on skin and mucosal surfaces. This article reviews currently used in vitro models of fungal infections ranging from cell monolayers to microfluidic 3D organ-on-chip (OOC) platforms. We also discuss how OOC models can expand the toolbox for investigating interactions of fungi and their human hosts in the future.

Isoquercitrin induces apoptosis and autophagy in hepatocellular carcinoma cells via AMPK/mTOR/p70S6K signaling pathway

Hepatocellular carcinoma (HCC) is an aggressive malignancy with high rates of metastasis and relapse. Isoquercitrin (ISO), a natural flavonoid present in the Chinese bayberry and other plant species, reportedly exerts notable inhibitory effects on tumor cell proliferation, though the mechanism is unknown. In the present study, we exposed HepG2 and Huh7 human liver cancer cells to ISO and examined the roles of autophagy and apoptosis in ISO-mediated cell death. We found that ISO exposure inhibited cell viability and colony growth, activated apoptotic pathway, and triggered dysregulated autophagy by activating the AMPK/mTOR/p70S6K pathway. Autophagy inhibition using 3-methyladenine (3-MA) or Atg5-targeted siRNA decreased the Bax/Bcl-2 ratio, caspase-3 activation, and PARP cleavage and protected cells against ISO-induced apoptosis. Moreover, autophagy inhibition reversed the upregulation of AMPK phosphorylation and downregulation of mTOR and p70S6K phosphorylation elicited by ISO. By contrast, application of a broad-spectrum caspase inhibitor failed to inhibit autophagy in ISO-treated cells. These data indicate that ISO simultaneously induced apoptosis and autophagy, and abnormal induction of autophagic flux contributed to ISO-triggered caspase-3-dependent apoptosis.

Design and Synthesis of 4(1H)-quinolone Derivatives as Autophagy Inducing Agents by Targeting ATG5 Protein

Background:

Quinolines have been characterized as a class of potential antitumor agents, and a large number of natural and synthetic quinolines acting as antitumor agents were reported.

Methods:

A series of 7-chloro-4(1H)-quinolone derivatives were synthesized. The antiproliferative effect of these compounds was evaluated by MTT assay against five human tumor cell lines. The mechanism of action of the selected compound 7h was also investigated.

Results and Discussion:

Most of the compounds had more potent antiproliferative activities than the lead compound 7-chloro-4(1H)-quinolone 6b. Compound 7h was found to be the most potent antiproliferative agent against human tumor cell lines. Further investigation demonstrated that compound 7h triggered ATG5-dependent autophagy of colorectal cancer cells by promoting the functions of LC3 proteins.

Conclusion:

These results were useful for designing and discovering more potent novel antitumor agents endowed with better pharmacological profiles.

Overexpression of miR‑30c‑5p reduces cellular cytotoxicity and inhibits the formation of kidney stones through ATG5

MicroRNAs (miRNAs or miRs) are critical regulators in various diseases. In the current study, the role of miR-30c-5p in the formation of sodium oxalate-induced kidney stones was investigated. For this purpose, human renal tubular epithelial cells (HK-2 cells) were incubated with sodium oxalate at the concentrations of 100, 250, 500, 750 and 1,000 µM. Cell viability and the miR-30c-5p expression level were respectively measured by CCK-8 assay and RT-qPCR. After separately transfecting miR-30c-5p mimic and inhibitor into the HK-2 cells, the cell apoptotic rate, the levels of mitochondrial membrane potential (MMP) and ROS were determined by flow cytometry. The levels of oxidative stress indicators [lactate dehydrogenase (LDH), malondialdehyde (MDA), superoxide dismutase (SOD) and catalase (CAT)] were determined using commercial kits. Crystal-cell adhesion assay was performed to evaluate the crystal adhesion capacity in vitro. miR-30c-5p binding at autophagy related 5 (ATG5) was predicted by TargetScan7.2 and further verified by dual-luciferase reporter assay. Rescue experiments were performed to confirm the molecular mechanisms underlying sodium oxalate-induced kidney formation in HK-2 cells. The results revealed that sodium oxalate decreased the viability of HK-2 cells in a concentration-dependent manner, and that miR-30c-5p expression was significantly downregulated by exposure to 750 µM sodium oxalate. In addition, the increase in cell apoptosis and crystal number, and the upregulated levels of LDH, MDA and ROS were reversed by the overexpression of miR-30c-5p. Moreover, the overexpression of miR-30c-5p upregulated the levels of SOD, CAT and MMP induced by sodium oxalate. ATG5 was directly regulated by miR-30c-5p, and the inhibition of cell cytotoxicity and crystal-cell adhesion induced by miR-30c-5p mimic was blocked by ATG5. These data indicated that the overexpression of miR-30c-5p alleviated cell cytotoxicity and crystal-cell adhesion induced by sodium oxalate through ATG5. Thus, the current study provides a better understanding of the role of miR-30c-5p in sodium oxalate-induced kidney stones.

Autophagy is essential for the endothelial differentiation of breast cancer stem‑like cells

Blood vessels serve an important role in tumor growth and metastasis, and recent studies have shown that certain tumor cancer stem cells may differentiate into endothelial cells and contribute to angiogenesis. In the present study, vascular endothelial growth factor (VEGF) was used to induce endothelial differentiation of breast cancer stem‑like cells (BCSLCs), and methods including flow cytometry, western blotting and immunofluorescence were used to study the relationship between autophagy and the endothelial differentiation of BCSLCs. The results showed that BCSLCs could differentiate into endothelial cells under the induction of VEGF in vitro. Subsequently, the role of autophagy in the endothelial differentiation of BCSLCs was examined. Autophagic activity was measured during endothelial differentiation of BCSLCs, and the association between autophagy and endothelial differentiation was investigated using autophagy activators, autophagy inhibitors and autophagy related 5 (Atg5)‑knockdown BCSLCs. Autophagy was increased during endothelial differentiation of BCSLCs, and there was a positive association between autophagy and endothelial differentiation. The ability of cells to undergo endothelial differentiation was reduced in BCSLCs with Atg5 knockdown. Therefore, autophagy was essential for endothelial differentiation of BCSLCs, and the findings of the present study may highlight novel potential avenues for reducing angiogenesis and improving treatment of breast cancer.

Contribution of Epithelial Cells to Defense Mechanisms in the Human Vagina

PURPOSE OF REVIEW

The vaginal milieu in women differs from that of other mammals, including non-human primates, in composition of secretions, the endogenous microbiota, and level of acidity. These changes apparently reflect evolutionary variations that maximized productive responses to a uniquely human vaginal environment. This review will highlight recent findings on properties of human vaginal epithelial cells that contribute to maintenance of a healthy vaginal environment.

RECENT FINDINGS

Vaginal epithelial cells are responsive to the composition of the vaginal microbiome even in women who are in apparently good health and do not exhibit any adverse physical symptoms. This is especially important during pregnancy when immune defenses are modified and an effective epithelial cell-derived anti-microbial activity is essential to prevent the migration to the uterus of bacteria potentially harmful to pregnancy progression. When Lactobacillus crispatus numerically predominates in the vagina, epithelial cell activity is low. Conversely, predominance of Lactobacillus iners, Gardnerella vaginalis, or other non-Lactobacilli evokes production and release of a large variety of compounds to minimize the potentially negative consequences of an altered microbiome. The extent of autophagy in vaginal epithelial cells, a basic process that functions to maintain intracellular homeostasis and engulf microbial invaders, is also sensitive to the external microbial environment Vaginal epithelial cells bind and release norepinephrine and upregulate their anti-microbial activity in response to external stress. Vaginal epithelial cells in women are responsive to local conditions that are unique to humans and, thereby, contribute to maintenance of a healthy milieu.