Autophagy and Mitochondrial Homeostasis During Infection: A Double-Edged Sword

Mechanistic insights into the kidney injury in chickens induced by hypervirulent fowl adenovirus serotype 4

Hypervirulent fowl adenovirus serotype 4 (FAdV-4) has emerged as a significant poultry pathogen since 2015, exhibiting clinical multi-organ and multi-tissue tropism post-infection, resulting in substantial economic losses in the poultry industry. However, the molecular mechanism underlying kidney injury caused by FAdV-4 infection remains unclear. Our results indicated that FAdV-4 infection in chickens induces damage to kidney tissues, characterized by the degeneration and necrosis of kidney epithelial cells, glomerular injury, endoplasmic reticulum stress, and the activation of a robust inflammatory response in the kidney cells. Notably, autophagosome-like vesicles enclosed clusters of viral particles that were transmitted between kidney cells post-infection. There might be a novel mechanism of vesicle-mediated cell-to-cell transmission of hypervirulent FAdV-4 that hijacks autophagosome-like vesicles. We also investigated cellular autophagy in kidney cells in vivo and in vitro during early FAdV-4 infection. The autophagy-related marker proteins LC3B, ATG5, and BECN1 were upregulated post-infection, whereas SQSTM1 was downregulated, indicating that FAdV-4 infection enhances autophagic flux and induces complete autophagy. The viral structural protein Fiber 2 was also observed to colocalize with the autophagy-related marker protein LC3B and the exosome-specific marker protein CD63 in the kidney cells at 24 hpi, suggesting that FAdV-4-induced cellular autophagy promotes viral replication in kidney cells and that autophagosome-like vesicles are involved in early FAdV-4 replication in vivo in chickens. Our results offer novel insights into the pathogenesis of hypervirulent FAdV-4 from the perspective of kidney injury post-infection.

IMPORTANCE

Hypervirulent fowl adenovirus serotype 4 (FAdV-4) has become globally prevalent since 2015 as a predominant pathogen on poultry farms, leading to substantial economic losses for the poultry industry. However, the molecular mechanisms underlying kidney injury induced by FAdV-4 infection remain unclear. In this study, we primarily elucidated the mechanisms of kidney injury induced by FAdV-4 infection in chickens, utilizing both in vitro and in vivo models. Our results demonstrate that FAdV-4 infection in chickens causes degeneration and necrosis of kidney epithelial cells, glomerular injury, and expansion of the endoplasmic reticulum, while also triggering a robust inflammatory response in kidney cells. Notably, we observed the cell-to-cell transmission of virus particles delivered by autophagosome-like vesicles, and the viral infection-induced cellular autophagy facilitated viral replication in the kidney cells. These findings offer a novel perspective to understand the molecular mechanisms of FAdV-4-induced kidney injury and establish a basis for further investigation into the molecular pathogenesis of hypervirulent FAdV-4.

Propyl acetate protects intestinal barrier during parenteral nutrition in mice and Caco-2 cells

BACKGROUND

Gut microbiota dysbiosis induces intestinal barrier damage during parenteral nutrition (PN). However, the underlying mechanisms remain unclear. This study aimed to investigate gut microbiota dysbiosis, luminal short-chain fatty acids, and autophagy in a mouse model and how these short-chain fatty acids regulate autophagy.

METHODS

Eight-week-old male specific-pathogen-free mice were randomly divided into a Chow group (standard diet and intravenous normal saline infusion) and a PN group (continuous infusion of PN nutrient solution) for 7 days. Caco-2 cells were also treated with intestinal rinse solutions from Chow and PN mouse models.

RESULTS

Compared with the Chow group, the PN group exhibited increased Proteobacteria and decreased Firmicutes, correlating with decreased propyl acetate. In the PN group, intestinal tissue exhibited elevated adenosine monophosphate-activated protein kinase (AMPK) phosphorylation, LC3II protein levels, and Atg3 and Atg7 messenger RNA levels. P62 protein levels were decreased, indicating an increase of autophagy flux in the PN group. In the Caco-2 cell model, cells treated with PN solution plus propyl acetate exhibited increased Claudin-1 and occluding along with decreased interleukin-6 and tumor necrosis factor α compared with those treated with PN solution alone. Propyl acetate addition inhibited the AMPK-mammalian target of rapamycin (mTOR) pathway, mitigating the excessive autophagy induced by the PN intestinal rinse solution in Caco-2 cells.

CONCLUSION

PN led to a significant reduction in propyl acetate levels in the intestine, excessive activation of autophagy, and barrier dysfunction. Propyl acetate inhibited excessive autophagy via the AMPK/mTOR signaling pathway and protected the intestinal barrier during PN.

Novel Approach to Skin Anti-Aging: Boosting Pharmacological Effects of Exogenous Nicotinamide Adenine Dinucleotide (NAD+) by Synergistic Inhibition of CD38 Expression

Nicotinamide adenine dinucleotide (NAD+) is indispensable for the regulation of biological metabolism. Previous studies have revealed its role in aging and degenerative diseases, while crucially showing that supplementation with NAD+ or its precursors could ameliorate or reverse the progression of aging. Despite extensive evidence for the role and action of NAD+ in aging, its pharmacological activity on the skin, or even its mechanism, has not been elucidated. In this study, we established a novel approach to effectively utilize NAD+ for skin anti-aging by enhancing the pharmacological efficacy of exogenous NAD+ using a phytochemical complex consisting of quercetin, and enoxolone through inhibition of CD38. Through the comprehensive in vitro experiments based on human fibroblasts, we observed that exogenous NAD+ could exert protective effects against both extrinsic aging induced by ultraviolet light exposure and intrinsic aging. Additionally, we found that its effects were significantly boosted by quercetin and enoxolone. In this in-depth study, we demonstrated that these beneficial effects are mediated by improved sirtuin activation, autophagy, and mitochondrial functionality. Our approach is expected to verify the applicability of the topical application of NAD+ and offer more effective solutions for the unmet needs of patients and consumers who demand more effective anti-aging effects.

Regulation of Autophagy Signaling Pathways by Ginseng Saponins: A Review

Ginseng saponins (ginsenosides), bioactive compounds derived from ginseng, are widely used natural products with potent therapeutic properties in the management of various ailments, particularly tumors, cardiovascular and cerebrovascular diseases, and immune system disorders. Autophagy, a highly regulated and multistep process involving the breakdown of impaired organelles and macromolecules by autophagolysosomes and autophagy-related genes (ATGs), has gained increasing attention as a potential target for ginsenoside-mediated disease treatment. This review aims to provide a comprehensive overview of recent research advances in the understanding of autophagy-related signaling pathways and the role of ginsenoside-mediated autophagy regulation. By delving into the intricate autophagy signaling pathways underpinning the pharmacological properties of ginsenosides, we highlight their therapeutic potential in addressing various conditions. Our findings serve as a comprehensive reference for further investigation into the medicinal properties of ginseng or ginseng-related products.

Spinetoram-Induced Potential Neurotoxicity through Autophagy Mediated by Mitochondrial Damage

Spinetoram is an important semi-synthetic insecticide extensively applied in agriculture. It is neurotoxic to insects, primarily by acting on acetylcholine receptors (nAChRs). However, few studies have examined the neurotoxicity of spinetoram in human beings. In this study, various concentrations (5, 10, 15, and 20 μM) of spinetoram were employed to expose SH-SY5Y cells in order to study the neurotoxic effects of spinetoram. The results showed that spinetoram exposure markedly inhibited cell viability and induced oxidative stress. It also induced mitochondrial membrane potential collapse (ΔΨm), and then caused a massive opening of the mitochondrial permeability transition pore (mPTP), a decrease in ATP synthesis, and Ca2+ overloading. Furthermore, spinetoram exposure induced cellular autophagy, as evidenced by the formation of autophagosomes, the conversion of LC3-I into LC3-II, down-regulation of p62, and up-regulation of beclin-1. In addition, we observed that p-mTOR expression decreased, while p-AMPK expression increased when exposed to spinetoram, indicating spinetoram triggered AMPK/mTOR-mediated autophagy. Complementarily, the effect of spinetoram on neurobehavior was studied using the zebrafish model. After being exposed to different concentrations (5, 10, and 20 μg/mL) of spinetoram, zebrafish showed neurobehavioral irregularities, such as reduced frequency of tail swings and spontaneous movements. Similarly, autophagy was also observed in zebrafish. In conclusion, spinetoram exposure produced potential neurotoxicity through autophagy mediated by mitochondrial damage. The experimental data and results of the neurotoxicity study of spinetoram provided above are intended to serve as reference for its safety assessment.

Curcumin/L-OHP co-loaded HAP for cGAS-STING pathway activation to enhance the natural immune response in colorectal cancer

Insufficient immune cell infiltration into the tumor microenvironment (TME) greatly compromises the clinical application of immune-checkpoint inhibitors (ICIs)-based immunotherapy. Recent findings have shown that activation of the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway can enhance natural immunity and increase lymphocyte infiltration into the TME, which presents a promising strategy for cancer immunotherapy. In this study, we constructed hydroxyapatite nanoparticles co-loaded with curcumin and L-oxaliplatin (Cur/L-OHP@HAP NPs). We analyzed the particle-size distribution, zeta potential, spectral characteristics (Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy), and drug-release properties of the Cur/L-OHP@HAP NPs. The cellular uptake of the Cur/L-OHP@HAP NPs detected by flow cytometry and confocal laser-scanning microscopy. We comprehensively evaluated the anti-tumor properties and immune-activating effects of the NPs, both in vitro and in vivo. Physicochemical characterizations demonstrated that the Cur/L-OHP@HAP NPs were successfully synthesized and were capable of pH-dependent drug release. Notably, the Cur/L-OHP@HAP NPs efficiently entered cancer cells, after which the released L-OHP induced nuclear DNA (nDNA) damage to some extent. HAP promoted the release of intracellular Ca2+ stores in cancer cells, and curcumin inhibited Ca2+ efflux, resulting in intracellular Ca2+ overload and the release of mitochondrial DNA (mtDNA). Damage to both nDNA and mtDNA greatly stimulated the cGAS-STING pathway, thereby activating natural immunity, accompanied by immune cell recruitment to the TME. In summary, the Cur/L-OHP@HAP NPs show good prospects for improving cancer immunotherapy.

Stachydrine Relieved the Inflammation and Promoted the Autophagy in Diabetes Retinopathy Through Activating the AMPK/SIRT1 Signaling Pathway

Background

Diabetes retinopathy (DR) is a chronic, progressive, and potentially harmful retinal disease associated with persistent hyperglycemia. Autophagy is a lysosome-dependent degradation pathway that widely exists in eukaryotic cells, which has recently been demonstrated to participate in the DR development. Stachydrine (STA) is a water-soluble alkaloid extracted from Leonurus heterophyllus. This study aimed to explore the effects of STA on the autophagy in DR progression in vivo and in vitro.

Methods

High glucose-treated human retinal microvascular endothelial cells (HRMECs) and STA-treated rats were used to establish DR model. The reactive oxygen species (ROS) and inflammatory factor levels (TNF-α, IL-1β, and IL-6) were determined using corresponding kits. Additionally, the cell growth was analyzed using CCK-8 and EdU assays. Besides, LC3BII, p62, p-AMPKα, AMPKα, and SIRT1 protein levels were measured using Western blot. The LC3BII and SIRT1 expressions were also determined using immunofluorescence.

Results

The results showed that STZ decreased the ROS and inflammatory factor levels in the HG-treated HRMECs. Besides, after STA treatment, the beclin-1, LC3BII, p-AMPKα, and SIRT1 levels were increased, and p62 was decreased in the HG-treated HRMECs and the retinal tissue of STZ-treated rats.

Conclusion

In conclusion, this study demonstrated that STA effectively relieved the inflammation and promoted the autophagy in DR progression in vivo and in vitro through activating the AMPK/SIRT1 signaling pathway.

TLR4 Overexpression Aggravates Bacterial Lipopolysaccharide-Induced Apoptosis via Excessive Autophagy and NF-κB/MAPK Signaling in Transgenic Mammal Models

Gram-negative bacterial infections pose a significant threat to public health. Toll-like receptor 4 (TLR4) recognizes bacterial lipopolysaccharide (LPS) and induces innate immune responses, autophagy, and cell death, which have major impacts on the body's physiological homeostasis. However, the role of TLR4 in bacterial LPS-induced autophagy and apoptosis in large mammals, which are closer to humans than rodents in many physiological characteristics, remains unknown. So far, few reports focus on the relationship between TLR, autophagy, and apoptosis in large mammal levels, and we urgently need more tools to further explore their crosstalk. Here, we generated a TLR4-enriched mammal model (sheep) and found that a high-dose LPS treatment blocked autophagic degradation and caused strong innate immune responses and severe apoptosis in monocytes/macrophages of transgenic offspring. Excessive accumulation of autophagosomes/autolysosomes might contribute to LPS-induced apoptosis in monocytes/macrophages of transgenic animals. Further study demonstrated that inhibiting TLR4 downstream NF-κB or p38 MAPK signaling pathways reversed the LPS-induced autophagy activity and apoptosis. These results indicate that the elevated TLR4 aggravates LPS-induced monocytes/macrophages apoptosis by leading to lysosomal dysfunction and impaired autophagic flux, which is associated with TLR4 downstream NF-κB and MAPK signaling pathways. This study provides a novel TLR4-enriched mammal model to study its potential effects on autophagy activity, inflammation, oxidative stress, and cell death. These findings also enrich the biological functions of TLR4 and provide powerful evidence for bacterial infection.

Role of Ceramide Synthase 1 in Oral Leukoplakia and Oral Squamous Cell Carcinoma: A Potential Linchpin for Tumorigenesis

Background Ceramide (CER), known as a "tumor suppressor lipid," plays a crucial role in promoting apoptosis in cancer cells. Ceramide synthase 1 (CERS1), an enzyme responsible for CER synthesis, holds immense importance. Notably, studies have highlighted that reduced levels of CERS1 confer protection to oral squamous cell carcinoma (OSCC) cells against chemotherapeutic agents like cisplatin. However, there is a scarcity of literature exploring the precise role of CERS1 in OSCC. Further investigation is warranted to unravel the intricate relationship of CERS1 in malignant transformation. Aim To compare the salivary CERS1 levels in OSCC, oral leukoplakia (OLK), and healthy individuals. Materials and methods Salivary samples from 15 healthy individuals, OLK patients, and OSCC patients each were obtained and an enzyme-linked immunosorbent assay (ELISA) (MyBioSource, Inc., San Diego, CA) was performed to evaluate salivary CERS1 enzyme levels. Descriptive statistics and Kruskal-Wallis analysis were done using SPSS v23.0 software (IBM Corp., Armonk, NY). Results There was a significant decrease in salivary CERS1 enzyme levels in OSCC (2.08 +/- 0.36 ng/dl) compared to healthy individuals (6.42 +/- 0.42 ng/dl) and OLK patients (4.73 +/- 0.93 ng/dl) (p = 0.05). Conclusion In this study, it was found that CERS1 shows a steady decrease in OLK and OSCC. Further cohort studies with larger sample sizes are needed to provide a basis for the role of CERS1 in OLK and its malignant transformation to OSCC.

Natural products targeting signaling pathways associated with regulated cell death in gastric cancer: Recent advances and perspectives

Gastric cancer (GC) is one of the most serious gastrointestinal malignancies with high morbidity and mortality. The complexity of GC process lies in the multi-phenotypic linkage regulation, in which regulatory cell death (RCD) is the core link, which largely dominates the fate of GC cells and becomes a key determinant of GC development and prognosis. In recent years, increasing evidence has been reported that natural products can prevent and inhibit the development of GC by regulating RCDs, showing great therapeutic potential. In order to further clarify its key regulatory characteristics, this review focused on specific expressions of RCDs, combined with a variety of signaling pathways and their crosstalk characteristics, sorted out the key targets and action rules of natural products targeting RCD. It is highlighted that a variety of core biological pathways and core targets are involved in the decision of GC cell fate, including the PI3K/Akt signaling pathway, MAPK-related signaling pathways, p53 signaling pathway, ER stress, Caspase-8, gasdermin D (GSDMD), and so on. Moreover, natural products target the crosstalk of different RCDs by modulating above signaling pathways. Taken together, these findings suggest that targeting various RCDs in GC with natural products is a promising strategy, providing a reference for further clarifying the molecular mechanism of natural products treating GC, which warrants further investigations in this area.

Deubiquitylase PSMD14 inhibits autophagy to promote ovarian cancer progression via stabilization of LRPPRC

Autophagy is a key cellular process, which exists in many tumors and plays dual roles in tumor promotion and suppression. However, the role and mechanism of aberrant autophagy in ovarian cancer remains unclear. Ubiquitin-proteasome pathway is the most important pathway for specific protein degradation. Deubiquitinases (DUBs) have crucial roles in all the stages of tumorigenesis and progression. Herein, we explore the DUBs which contribute to aberrant autophagy in ovarian cancer. TCGA data analysis shows that the autophagy level is suppressed, and the selective autophagy receptor SQSTM1/p62 is abnormally high expressed in ovarian cancer. We screen and identify that the deubiquitinase PSMD14 negatively regulates autophagy level. Functional studies show that increased PSMD14 expression remarkably enhances ovarian cancer cells malignancy, whereas knockdown of PSMD14 has the opposite effect. Furthermore, in vivo assays show that knockdown of PSMD14 inhibits the growth, lung and abdominal metastasis of ovarian cancer. Mechanistically, PSMD14 directly interacts with LRPPRC and inhibits its ubiquitination, thereby inhibiting autophagy through LRPPRC/Beclin1-Bcl-2/SQSTM1 signaling pathway. Next, we demonstrate that PSMD14 is upregulated in ovarian cancer and high expression of PSMD14 positively correlates with LRPPRC. Taken together, we clarify the role of autophagy in regulating the ovarian cancer phenotype and provide insights into regulatory mechanism of autophagy in ovarian cancer.

Role of Enterococcus faecalis in refractory apical periodontitis: from pathogenicity to host cell response

BACKGROUND

Refractory apical periodontitis (RAP) is an oral infectious disease characterised by persistent inflammation, progressive alveolar bone destruction, and delayed bone healing. RAP has received increasing attention, because it cannot be cured after repeated root canal therapies. The aetiology of RAP is related to the complex interplay between the pathogen and its host. However, the exact pathogenesis of RAP remains unclarified and includes several factors, such as microorganism immunogenicity, host immunity and inflammation, and tissue destruction and repair. Enterococcus faecalis is the dominant pathogen involved in RAP, and has evolved multiple strategies to ensure survival, which cause persistent intraradicular and extraradicular infections.

OBJECTIVE

To review the crucial role of E. faecalis in the pathogenesis of RAP, and open new avenues for prevention and treatment of RAP.

METHODS

The PubMed and Web of Science databases were searched for pertinent publications, employing the search terms "Enterococcus faecalis", "refractory apical periodontitis", "persistent periapical periodontitis", "pathogenicity", "virulence", "biofilm formation", "dentine tubule", "immune cell", "macrophage", and "osteoblast".

RESULTS AND CONCLUSION

Besides its high pathogenicity due to various virulence mechanisms, E. faecalis modulates the macrophage and osteoblast responses, including regulated cell death, cell polarisation, cell differentiation, and inflammatory response. An in-depth understanding of the multifaceted host cell responses modulated by E. faecalis will help to design potential future therapeutic strategies and overcome the challenges of sustained infection and delayed tissue healing in RAP.

Novel Therapeutic Strategies for Ischemic Stroke: Recent Insights into Autophagy

Stroke is one of the leading causes of death and disability worldwide. Autophagy is a conserved cellular catabolic pathway that maintains cellular homeostasis by removal of damaged proteins and organelles, which is critical for the maintenance of energy and function homeostasis of cells. Accumulating evidence demonstrates that autophagy plays important roles in pathophysiological mechanisms under ischemic stroke. Previous investigations show that autophagy serves as a “double-edged sword” in ischemic stroke as it can either promote the survival of neuronal cells or induce cell death in special conditions. Following ischemic stroke, autophagy is activated or inhibited in several cell types in brain, including neurons, astrocytes, and microglia, as well as microvascular endothelial cells, which involves in inflammatory activation, modulation of microglial phenotypes, and blood-brain barrier permeability. However, the exact mechanisms of underlying the role of autophagy in ischemic stroke are not fully understood. This review focuses on the recent advances regarding potential molecular mechanisms of autophagy in different cell types. The focus is also on discussing the “double-edged sword” effect of autophagy in ischemic stroke and its possible underlying mechanisms. In addition, potential therapeutic strategies for ischemic stroke targeting autophagy are also reviewed.

Diallyl Trisulfide Enhances the Survival of Multiterritory Perforator Skin Flaps

The multiterritory perforator flap is one of the widest flap patterns used to repair tissue defects. However, flap necrosis of the distal part is still a challenging issue for plastic surgeons. Diallyl trisulfide (DATS) is an efficient ingredient extracted from garlic, exerting many important effects on different diseases. Our experiment aims to reveal whether DATS has a beneficial effect on the survival of perforator flaps and to explore its mechanism of action. The results showed that DATS enhanced angiogenesis and autophagy and reduced cell apoptosis and oxidative stress, thereby improving the survival rate of skin flaps. After co-administration with autophagy inhibitor 3-methyladenine (3MA), perforator flap survival was further improved. Mechanistically, we showed that PI3K/Akt and AMPK-HIF-1α signaling pathways in flap were activated under DATS treatment. All in all, DATS promoted the survival of multiterritory perforator flaps via the synergistic regulation of PI3K/Akt and AMPK-HIF-1α signaling pathways, and inhibition of DATS-induced autophagy further improves flap survival.