Tumor-repopulating cells evade ferroptosis via PCK2-dependent phospholipid remodeling.

Whether stem-cell-like cancer cells avert ferroptosis to mediate therapy resistance remains unclear. In this study, using a soft fibrin gel culture system, we found that tumor-repopulating cells (TRCs) with stem-cell-like cancer cell characteristics resist chemotherapy and radiotherapy by decreasing ferroptosis sensitivity. Mechanistically, through quantitative mass spectrometry and lipidomic analysis, we determined that mitochondria metabolic kinase PCK2 phosphorylates and activates ACSL4 to drive ferroptosis-associated phospholipid remodeling. TRCs downregulate the PCK2 expression to confer themselves on a structural ferroptosis-resistant state. Notably, in addition to confirming the role of PCK2-pACSL4(T679) in multiple preclinical models, we discovered that higher PCK2 and pACSL4(T679) levels are correlated with better response to chemotherapy and radiotherapy as well as lower distant metastasis in nasopharyngeal carcinoma cohorts.

Mitigating phospholipid peroxidation of macrophages in stress-induced tumor microenvironment by natural ALOX15/PEBP1 complex inhibitors.

BACKGROUND: The intricate interactions between chronic psychological stress and susceptibility to breast cancer have been recognized, yet the underlying mechanisms remain unexplored. Danzhi Xiaoyao Powder (DZXY), a traditional Chinese medicine (TCM) formula, has found clinical utility in the treatment of breast cancer. Macrophages, as the predominant immune cell population within the tumor microenvironment (TME), play a pivotal role in orchestrating tumor immunosurveillance. Emerging evidence suggests that lipid oxidation accumulation in TME macrophages, plays a critical role in breast cancer development and progression. However, a comprehensive understanding of the pharmacological mechanisms and active components of DZXY related to its clinical application in the treatment of stress-aggravated breast cancer remains elusive. PURPOSE: This study sought to explore the plausible regulatory mechanisms and identify the key active components of DZXY contributing to its therapeutic efficacy in the context of breast cancer. METHODS: Initially, we conducted an investigation into the relationship between the phagocytic capacity of macrophages damaged by psychological stress and phospholipid peroxidation using flow cytometry and LC-MS/MS-based phospholipomics. Subsequently, we evaluated the therapeutic efficacy of DZXY based on the results of the tumor size, tumor weight, the phospholipid peroxidation pathway and phagocytosis of macrophage. Additionally, the target-mediated characterization strategy based on binding of arachidonate 15-lipoxygenase (ALOX15) to phosphatidylethanolamine-binding protein-1 (PEBP1), including molecular docking analysis, microscale thermophoresis (MST) assay, co-immunoprecipitation analysis and activity verification, has been further implemented to reveal the key bio-active components in DZXY. Finally, we evaluated the therapeutic efficacy of isochlorogenic acid C (ICAC) based on the results of tumor size, tumor weight, the phospholipid peroxidation pathway, and macrophage phagocytosis in vivo. RESULTS: The present study demonstrated that phospholipid peroxides, as determined by LC-MS/MS-based phospholipidomics, triggered in macrophages, which in turn compromised their capacity to eliminate tumor cells through phagocytosis. Furthermore, we elucidate the mechanism behind stress-induced PEBP1 to form a complex with ALOX15, thereby mediating membrane phospholipid peroxidation in macrophages. DZXY, demonstrates potent anti-breast cancer therapeutic effects by disrupting the ALOX15/PEBP1 interaction and inhibiting phospholipid peroxidation, ultimately enhancing macrophages' phagocytic capability towards tumor cells. Notably, ICAC emerged as a promising active component in DZXY, which can inhibit the ALOX15/PEBP1 interaction, thereby mitigating phospholipid peroxidation in macrophages. CONCLUSION: Collectively, our findings elucidate stress increases the susceptibility of breast cancer by driving lipid peroxidation of macrophages and suggest the ALOX15/PEBP1 complex as a promising intervention target for DZXY.

A ferroptosis-targeting ceria anchored halloysite as orally drug delivery system for radiation colitis therapy.

Radiation colitis is the leading cause of diarrhea and hematochezia in pelvic radiotherapy patients. This work advances the pathogenesis of radiation colitis from the perspective of ferroptosis. An oral Pickering emulsion is stabilized with halloysite clay nanotubes to alleviate radiation colitis by inhibiting ferroptosis. Ceria nanozyme grown in situ on nanotubes can scavenge reactive oxygen species, and deferiprone was loaded into the lumen of nanotubes to relieve iron stress. These two strategies effectively inhibit lipid peroxidation and rescue ferroptosis in the intestinal microenvironment. The clay nanotubes play a critical role as either a medicine to alleviate colitis, a nanocarrier that targets the inflamed colon by electrostatic adsorption, or an interfacial stabilizer for emulsions. This ferroptosis-based strategy was effective in vitro and in vivo, providing a prospective candidate for radiotherapy protection via rational regulation of specific oxidative stress.

Reducing lipid peroxidation attenuates stress-induced susceptibility to herpes simplex virus type 1.

Psychological stress increases the susceptibility to herpes simplex virus type 1 (HSV-1) infection. There is no effective intervention due to the unknown pathogenesis mechanisms. In this study we explored the molecular mechanisms underlying stress-induced HSV-1 susceptibility and the antiviral effect of a natural compound rosmarinic acid (RA) in vivo and in vitro. Mice were administered RA (11.7, 23.4 mg·kg-1·d-1, i.g.) or acyclovir (ACV, 206 mg·kg-1·d-1, i.g.) for 23 days. The mice were subjected to restraint stress for 7 days followed by intranasal infection with HSV-1 on D7. At the end of RA or ACV treatment, mouse plasma samples and brain tissues were collected for analysis. We showed that both RA and ACV treatment significantly decreased stress-augmented mortality and alleviated eye swelling and neurological symptoms in HSV-1-infected mice. In SH-SY5Y cells and PC12 cells exposed to the stress hormone corticosterone (CORT) plus HSV-1, RA (100 µM) significantly increased the cell viability, and inhibited CORT-induced elevation in the expression of viral proteins and genes. We demonstrated that CORT (50 µM) triggered lipoxygenase 15 (ALOX15)-mediated redox imbalance in the neuronal cells, increasing the level of 4-HNE-conjugated STING, which impaired STING translocation from the endoplasmic reticulum to Golgi; the abnormality of STING-mediated innate immunity led to HSV-1 susceptibility. We revealed that RA was an inhibitor of lipid peroxidation by directly targeting ALOX15, thus RA could rescue stress-weakened neuronal innate immune response, thereby reducing HSV-1 susceptibility in vivo and in vitro. This study illustrates the critical role of lipid peroxidation in stress-induced HSV-1 susceptibility and reveals the potential for developing RA as an effective intervention in anti-HSV-1 therapy.

GPX4 deficiency-dependent phospholipid peroxidation drives motor deficits of ALS.

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterized by oxidative stress that triggers motor neurons loss in the brain and spinal cord. However, the mechanisms underlying the exact role of oxidative stress in ALS-associated neural degeneration are not definitively established. Oxidative stress-generated phospholipid peroxides are known to have extensive physiological and pathological consequences to tissues. Here, we discovered that the deficiency of glutathione peroxidase 4 (GPX4), an essential antioxidant peroxidase, led to the accumulation of phospholipid peroxides and resulted in a loss of motor neurons in spinal cords of ALS mice. Mutant human SOD1G93A transgenic mice were intrathecally injected with neuron-targeted adeno-associated virus (AAV) expressing GPX4 (GPX4-AAV) or phospholipid peroxidation inhibitor, ferrostatin-1. The results showed that impaired motor performance and neural loss induced by SOD1G93A toxicity in the lumbar spine were substantially alleviated by ferrostatin-1 treatment and AAV-mediated GPX4 delivery. In addition, the denervation of neuron-muscle junction and spinal atrophy in ALS mice were rescued by neural GPX4 overexpression, suggesting that GPX4 is essential for the motor neural maintenance and function. In comparison, conditional knockdown of Gpx4 in the spinal cords of Gpx4fl/fl mice triggered an obvious increase of phospholipid peroxides and the occurrence of ALS-like motor phenotype. Altogether, our findings underscore the importance of GPX4 in maintaining phospholipid redox homeostasis in the spinal cord and presents GPX4 as an attractive therapeutic target for ALS treatment.

Tripeptide Leu-Pro-Phe from Corn Protein Hydrolysates Attenuates Hyperglycemia-Induced Neural Tube Defect in Chicken Embryos.

Neural tube defect (NTD) is the most common and severe embryopathy causing embryonic malformation and even death associated with gestational diabetes mellitus (GDM). Leu-Pro-Phe (LPF) is an antioxidative tripeptide isolated from hydrolysates of corn protein. However, the biological activity of LPF in vivo and in vitro remains unclear. This study is aimed at investigating the protective effects of tripeptide LPF against NTD in the high glucose exposure condition and delineate the underlying biological mechanism. We found that LPF alleviated NTD in the high glucose-exposed chicken embryo model. In addition, DF-1 chicken embryo fibroblast was loaded with high glucose for induction of oxidative stress and abnormal O-GlcNAcylation in vitro. LPF significantly decreased accumulation of reactive oxygen species and content of malondialdehyde in DF-1 cells but increased the ratio of reduced glutathione and oxidized glutathione in chick embryo. Oxygen radical absorbance capacity results showed that LPF itself had good free radical scavenging capacity and could enhance antioxidant activity of the cell content. Mechanistic studies suggested that the resistance of LPF to oxidative damage may be related to promotion of NRF2 expression and nuclear translocation. LPF alleviated the overall O-GlcNAcylation level of cellular proteins under high glucose conditions and restored the level of Pax3 protein. Collectively, our findings indicate that LPF peptide could act as a nutritional supplement for the protection of development of embryonic neural tube affected by GDM.

Phospholipid peroxidation inhibits autophagy via stimulating the delipidation of oxidized LC3-PE.

Phospholipid peroxidation of polyunsaturated fatty acids at the bis-allylic position drives ferroptosis. Here we identify a novel role for phospholipid peroxidation in the inhibition of autophagy. Using in vitro and in vivo models, we report that phospholipid peroxidation induced by glutathione peroxidase-4 inhibition and arachidonate 15-lipoxygenase overexpression leads to overload of peroxidized phospholipids and culminate in inhibition of autophagy. Functional and lipidomics analysis further demonstrated that inhibition of autophagy was associated with an increase of peroxidized phosphatidylethanolamine (PE) conjugated LC3. We further demonstrate that autophagy inhibition occurred due to preferential cleavage of peroxidized LC3-PE by ATG4B to yield delipidated LC3. Mouse models of phospholipid peroxidation and autophagy additionally supported a role for peroxidized PE in autophagy inhibition. Our results agree with the recognized role of endoplasmic reticulum as the primary source for autophagosomal membranes. In summary, our studies demonstrated that phospholipid peroxidation inhibited autophagy via stimulating the ATG4B-mediated delipidation of peroxidized LC3-PE.

Cyclo(-Phe-Phe) alleviates chick embryo liver injury via activating the Nrf2 pathway.

Excessive reactive oxygen species (ROS) accumulation is involved in the pathogenesis of liver fibrosis and damage, specifically in the developing embryo that is extremely sensitive to oxidative stress. Herein, a liver injury model in chick embryo was established by using 2,2-azobis (2-amidinopropane) dihydrochloride (AAPH), which was used to investigate the effect of cyclo(-Phe-Phe) (CPP), a natural dipeptide found in foods and beverages. The results showed that CPP significantly alleviated AAPH-induced liver pathological damage, hepatic dysfunction and inhibited the excessive production of ROS in both chick embryo liver and HepG2 cells. Additionally, CPP increased the antioxidative activity of glutathione peroxidase (GPx) and superoxide dismutase (SOD), as well as elevated the level of glutathione (GSH), suggesting that CPP combating liver injury probably depends on its antioxidant capability. Mechanistically, CPP upregulated the mRNA and protein expression of heme oxyense-1 (HO-1) and NADPH quinone oxidoreductase 1 (NQO1) in vivo and in vitro, along with promoting the translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) while inhibiting its degradation through binding with Kelch-like ECH-associated protein 1 (Keap1). In conclusion, this study proposes a potential peptide drug for the treatment of hepatic damage induced by oxidative stress and also unravels its mechanism of action.

The disbalance of LRP1 and SIRPα by psychological stress dampens the clearance of tumor cells by macrophages.

The relationship between chronic psychological stress and tumorigenesis has been well defined in epidemiological studies; however, the underlying mechanism remains underexplored. In this study, we discovered that impaired macrophage phagocytosis contributed to the psychological stress-evoked tumor susceptibility, and the stress hormone glucocorticoid (GC) was identified as a principal detrimental factor. Mechanistically, GC disturbed the balance of the "eat me" signal receptor (low-density lipoprotein receptor-related protein-1, LRP1) and the "don't eat me" signal receptor (signal regulatory protein alpha, SIRPα). Further analysis revealed that GC led to a direct, glucocorticoid receptor (GR)-dependent trans-repression of LRP1 expression, and the repressed LRP1, in turn, resulted in the elevated gene level of SIRPα by down-regulating miRNA-4695-3p. These data collectively demonstrate that stress induces the imbalance of the LRP1/SIRPα axis and entails the disturbance of tumor cell clearance by macrophages. Our findings provide the mechanistic insight into psychological stress-evoked tumor susceptibility and indicate that the balance of LRP1/SIRPα axis may serve as a potential therapeutic strategy for tumor treatment.

Successive High-Resolution (H2O)n-GCIB and C60-SIMS Imaging Integrates Multi-Omics in Different Cell Types in Breast Cancer Tissue.

The temporo-spatial organization of different cells in the tumor microenvironment (TME) is the key to understanding their complex communication networks and the immune landscape that exists within compromised tissues. Multi-omics profiling of single-interacting cells in the native TME is critical for providing further information regarding the reprograming mechanisms leading to immunosuppression and tumor progression. This requires new technologies for biomolecular profiling of phenotypically heterogeneous cells on the same tissue sample. Here, we developed a new methodology for comprehensive lipidomic and metabolomic profiling of individual cells on frozen-hydrated tissue sections using water gas cluster ion beam secondary ion mass spectrometry ((H2O)n-GCIB-SIMS) (at 1.6 µm beam spot size), followed by profiling cell-type specific lanthanide antibodies on the same tissue section using C60-SIMS (at 1.1 µm beam spot size). We revealed distinct variations of distribution and intensities of >150 key ions (e.g., lipids and important metabolites) in different types of the TME individual cells, such as actively proliferating tumor cells as well as infiltrating immune cells. The demonstrated feasibility of SIMS imaging to integrate the multi-omics profiling in the same tissue section at the single-cell level will lead to new insights into the role of lipid reprogramming and metabolic response in normal regulation or pathogenic discoordination of cell-cell interactions in a variety of tissue microenvironments.

Theacrine, a Potent Antidepressant Purine Alkaloid from a Special Chinese Tea, Promotes Adult Hippocampal Neurogenesis in Stressed Mice.

Daily intake of tea has been known to relate to a low risk of depression. In this study, we report that a special variety of tea in China, Camellia assamica var. kucha (kucha), possesses antidepressant effects but with less adverse effects as compared to traditional tea Camellia sinensis. This action of kucha is related to its high amount of theacrine, a purine alkaloid structurally similar to caffeine. We investigated the antidepressant-like effects and mechanisms of theacrine in chronic water immersion restraint stress and chronic unpredictable mild stress mice models. PC12 cells and primary hippocampal neural stem cells were treated with stress hormone corticosterone (CORT) to reveal the potential antidepression mechanism of theacrine from the perspective of adult hippocampus neurogenesis. Results of behavioral and neurotransmitter analysis showed that intragastric administration of theacrine significantly counteracted chronic stress-induced depression-like disorders and abnormal 5-hydroxytryptamine (5-HT) metabolism with less central excitability. Further investigation from both in vivo and in vitro experiments indicated that the antidepressant mechanism of theacrine was associated with promoting adult hippocampal neurogenesis, via the modulation of the phosphodiesterase-4 (PDE4)/cyclic adenosine monophosphate (cAMP)/cAMP response-element binding (CREB)/brain-derived neurotrophic factor (BDNF)/tropomyosin-related kinase B (TrkB) pathway. Collectively, our findings could promote the prevalence of kucha as a common beverage with uses for health care and contribute to the development of theacrine as a potential novel antidepressant medicine.

Direct Mapping of Phospholipid Ferroptotic Death Signals in Cells and Tissues by Gas Cluster Ion Beam Secondary Ion Mass Spectrometry (GCIB-SIMS).

Peroxidized phosphatidylethanolamine (PEox) species have been identified by liquid chromatography mass spectrometry (LC-MS) as predictive biomarkers of ferroptosis, a new program of regulated cell death. However, the presence and subcellular distribution of PEox in specific cell types and tissues have not been directly detected by imaging protocols. By applying gas cluster ion beam secondary ion mass spectrometry (GCIB-SIMS) imaging with a 70 keV (H2 O)n+ (n>28 000) cluster ion beam, we were able to map PEox with 1.2 µm spatial resolution at the single cell/subcellular level in ferroptotic H9c2 cardiomyocytes and cortical/hippocampal neurons after traumatic brain injury. Application of this protocol affords visualization of physiologically relevant levels of very low abundance (20 pmol µmol-1 lipid) peroxidized lipids in subcellular compartments and their accumulation in disease conditions.

Oxygenated phosphatidylethanolamine navigates phagocytosis of ferroptotic cells by interacting with TLR2.

During cancer therapy, phagocytic clearance of dead cells plays a vital role in immune homeostasis. The nonapoptotic form of cell death, ferroptosis, exhibits extraordinary potential in tumor treatment. However, the phagocytosis mechanism that regulates the engulfment of ferroptotic cells remains unclear. Here, we establish a novel pathway for phagocytic clearance of ferroptotic cells that is different from canonical mechanisms by using diverse ferroptosis models evoked by GPX4 dysfunction/deficiency. We identified the oxidized phospholipid, 1-steaoryl-2-15-HpETE-sn-glycero-3-phosphatidylethanolamine (SAPE-OOH), as a key eat-me signal on the ferroptotic cell surface. Enriching the plasma membrane with SAPE-OOH increased the efficiency of phagocytosis of ferroptotic cells by macrophage, a process that was suppressed by lipoprotein-associated phospholipase A2. Ligand fishing, lipid blotting, and cellular thermal shift assay screened and identified TLR2 as a membrane receptor that directly recognized SAPE-OOH, which was further confirmed by TLR2 inhibitors and gene silencing studies. A mouse mammary tumor model of ferroptosis verified SAPE-OOH and TLR2 as critical players in the clearance of ferroptotic cells in vivo. Taken together, this work demonstrates that SAPE-OOH on ferroptotic cell surface acts as an eat-me signal and navigates phagocytosis by targeting TLR2 on macrophages.

Selective autophagy of intracellular organelles: recent research advances.

Macroautophagy (hereafter called autophagy) is a highly conserved physiological process that degrades over-abundant or damaged organelles, large protein aggregates and invading pathogens via the lysosomal system (the vacuole in plants and yeast). Autophagy is generally induced by stress, such as oxygen-, energy- or amino acid-deprivation, irradiation, drugs, etc. In addition to non-selective bulk degradation, autophagy also occurs in a selective manner, recycling specific organelles, such as mitochondria, peroxisomes, ribosomes, endoplasmic reticulum (ER), lysosomes, nuclei, proteasomes and lipid droplets (LDs). This capability makes selective autophagy a major process in maintaining cellular homeostasis. The dysfunction of selective autophagy is implicated in neurodegenerative diseases (NDDs), tumorigenesis, metabolic disorders, heart failure, etc. Considering the importance of selective autophagy in cell biology, we systemically review the recent advances in our understanding of this process and its regulatory mechanisms. We emphasize the 'cargo-ligand-receptor' model in selective autophagy for specific organelles or cellular components in yeast and mammals, with a focus on mitophagy and ER-phagy, which are finely described as types of selective autophagy. Additionally, we highlight unanswered questions in the field, helping readers focus on the research blind spots that need to be broken.

Autophagy-dependent removal of α-synuclein: a novel mechanism of GM1 ganglioside neuroprotection against Parkinson's disease.

GM1 ganglioside is particularly abundant in the mammalian central nervous system and has shown beneficial effects on neurodegenerative diseases. In this study, we investigated the therapeutic effect of GM1 ganglioside in experimental models of Parkinson's disease (PD) in vivo and in vitro. Mice were injected with MPTP (30 mg·kg-1·d-1, i.p.) for 5 days, resulting in a subacute model of PD. PD mice were treated with GM1 ganglioside (25, 50 mg·kg-1·d-1, i.p.) for 2 weeks. We showed that GM1 ganglioside administration substantially improved the MPTP-induced behavioral disturbance and increased the levels of dopamine and its metabolites in the striatal tissues. In the MPP+-treated SH-SY5Y cells and α-synuclein (α-Syn) A53T-overexpressing PC12 (PC12α-Syn A53T) cells, treatment with GM1 ganglioside (40 µM) significantly decreased α-Syn accumulation and alleviated mitochondrial dysfunction and oxidative stress. We further revealed that treatment with GM1 ganglioside promoted autophagy, evidenced by the autophagosomes that appeared in the substantia nigra of PD mice as well as the changes of autophagy-related proteins (LC3-II and p62) in the MPP+-treated SH-SY5Y cells. Cotreatment with the autophagy inhibitor 3-MA or bafilomycin A1 abrogated the in vivo and in vitro neuroprotective effects of GM1 ganglioside. Using GM1 ganglioside labeled with FITC fluorescent, we observed apparent colocalization of GM1-FITC and α-Syn as well as GM1-FITC and LC3 in PC12α-Syn A53T cells. GM1 ganglioside significantly increased the phosphorylation of autophagy regulatory proteins ATG13 and ULK1 in doxycycline-treated PC12α-Syn A53T cells and the MPP+-treated SH-SY5Y cells, which was inhibited by 3-MA. Taken together, this study demonstrates that the anti-PD role of GM1 ganglioside resulted from activation of autophagy-dependent α-Syn clearance.

Celastrol ameliorates Propionibacterium acnes/LPS-induced liver damage and MSU-induced gouty arthritis via inhibiting K63 deubiquitination of NLRP3.

BACKGROUND: Celastrol, a pentacyclic triterpenoid quinonemethide isolated from several spp. of Celastraceae family, exhibits anti-inflammatory activities in a variety of diseases including arthritis. PURPOSE: This study aims to investigate whether the inhibition of NLRP3 inflammasome is engaged in the anti-inflammatory activities of celastrol and delineate the underlying mechanism. METHODS: The influence of celastrol on NLRP3 inflammasome activation was firstly studied in lipopolysaccharide (LPS)-primed mouse bone marrow-derived macrophages (BMDMs) and phorbol 12-myristate 13-acetate (PMA)-primed THP-1 cells treated with nigericin. Reconstituted inflammasome was also established by co-transfecting NLRP3, ASC, pro-caspase-1 and pro-IL-1ß in HEK293T cells. The changes of inflammasome components including NLRP3, ASC, pro-caspase-1/caspase-1 and pro-IL-1ß/IL-1ß were examined by enzyme-linked immunosorbent assay (ELISA), western blotting and immunofluorescence. Furthermore, Propionibacterium acnes (P. acnes)/LPS-induced liver injury and monosodium urate (MSU)-induced gouty arthritis in mice were employed in vivo to validate the inhibitory effect of celastrol on NLRP3 inflammasome. RESULTS: Celastrol significantly suppressed the cleavage of pro-caspase-1 and pro-IL-1ß, while not affecting the protein expressions of NLRP3, ASC, pro-caspase-1 and pro-IL-1ß in THP-1 cells, BMDMs and HEK293T cells. Celastrol suppressed NLRP3 inflammasome activation and alleviated P. acnes/LPS-induced liver damage and MSU-induced gouty arthritis. Mechanism study revealed that celastrol could interdict K63 deubiquitination of NLRP3, which may concern interaction of celastrol and BRCA1/BRCA2-containing complex subunit 3 (BRCC3), and thereby prohibited the formation of NLRP3, ASC and pro-caspase-1 complex to block the generation of mature IL-1ß. CONCLUSION: Celastrol suppresses NLRP3 inflammasome activation in P. acnes/LPS-induced liver damage and MSU-induced gouty arthritis via inhibiting K63 deubiquitination of NLRP3, which presents a novel insight into inhibition of celastrol on NLRP3 inflammasome and provides more evidences for its application in the therapy of inflammation-related diseases.

Inhibitory effects of baicalein against herpes simplex virus type 1.

Herpes simplex virus type 1 (HSV-1) is a ubiquitous and widespread human pathogen, which gives rise to a range of diseases, including cold sores, corneal blindness, and encephalitis. Currently, the use of nucleoside analogs, such as acyclovir and penciclovir, in treating HSV-1 infection often presents limitation due to their side effects and low efficacy for drug-resistance strains. Therefore, new anti-herpetic drugs and strategies should be urgently developed. Here, we reported that baicalein, a naturally derived compound widely used in Asian countries, strongly inhibited HSV-1 replication in several models. Baicalein was effective against the replication of both HSV-1/F and HSV-1/Blue (an acyclovir-resistant strain) in vitro. In the ocular inoculation mice model, baicalein markedly reduced in vivo HSV-1/F replication, receded inflammatory storm and attenuated histological changes in the cornea. Consistently, baicalein was found to reduce the mortality of mice, viral loads both in nose and trigeminal ganglia in HSV-1 intranasal infection model. Moreover, an ex vivo HSV-1-EGFP infection model established in isolated murine epidermal sheets confirmed that baicalein suppressed HSV-1 replication. Further investigations unraveled that dual mechanisms, inactivating viral particles and inhibiting IκB kinase beta (IKK-ß) phosphorylation, were involved in the anti-HSV-1 effect of baicalein. Collectively, our findings identified baicalein as a promising therapy candidate against the infection of HSV-1, especially acyclovir-resistant strain.

Autophagic degradation of PML promotes susceptibility to HSV-1 by stress-induced corticosterone.

Rationale: Herpes simplex virus type 1 (HSV-1) is a neurotropic virus that can cause a variety of clinical syndromes including mucocutaneous disease and HSV-1 encephalitis (HSE). Here, we characterize the molecular mechanisms underlying the susceptibility to HSV-1 under stressful conditions. Methods: Restraint stress and corticosterone (CORT, a primary stress hormone) were respectively used to establish HSV-1 susceptible model in vivo and in vitro. Viral titers were determined by plaque assay. Western blotting, immunofluorescence, transmission electron microscopy (TEM), qRT-PCR, H&E staining, IHC staining and flow cytometry were employed to evaluate virus-related protein expressions and detect the activation of autophagy. Loss- and gain-function assays, co-immunoprecipitation (co-IP) technique and autophagy agonist/antagonist treatments were applied in mechanistic experiments. Results: Restraint stress increased the susceptibility of mouse brain to HSV-1. Similarly, CORT treatment enhanced the susceptibility of neural cells to HSV-1. Furthermore, PML protein level in HSV-1 infected brain tissues and neural cells was remarkably decreased by stress treatment in vivo or CORT treatment in vitro, while its transcriptional level was not affected. Notably, a striking decline in protein expressions of ICP27 and gB was observed in PML-overexpressing cells, which was reversed by CORT treatment. By contrast, protein expression of gB was increased by knockdown with si-PML in virus-infected SH-SY5Y cells. We further discovered that CORT-driven PML degradation was dependent on the activation of autophagy in a ULK1-independent manner, rather than proteasome pathway. Bafilomycin A1 (BaF1) attenuated the augmentation effect of CORT on HSV-1 infection. The expressions of viral proteins were reduced in LC3-depleted cells, and the degradation of PML by CORT-induced autophagy was prevented in cells with LC3 knockdown by RNAi. Interestingly, PML was revealed to interact with the autophagic cargo receptor P62 and the autophagic effector protein LC3. Additionally, CORT failed to increase gB protein level when PML was silenced, providing direct evidence linking autophagic degradation of PML and CORT-induced virus susceptibility. Conclusion: Our results revealed that restraint stress/CORT increased HSV-1 susceptibility by delivering PML into autolysosomes for degradation. The results obtained from in vitro and in vivo models not only demonstrated the adverse effects of stress on HSV-1 infection, but also systematically investigated the underlying molecular mechanisms. These discoveries broaden our understanding of the interplay between host and viruses, and a comprehensive understanding of the role of autophagy in viral infection will provide information for future development of innovative drugs against viral infection.

Mitochondrial Sirtuin 3: New emerging biological function and therapeutic target.

Sirtuin 3 (SIRT3) is one of the most prominent deacetylases that can regulate acetylation levels in mitochondria, which are essential for eukaryotic life and inextricably linked to the metabolism of multiple organs. Hitherto, SIRT3 has been substantiated to be involved in almost all aspects of mitochondrial metabolism and homeostasis, protecting mitochondria from a variety of damage. Accumulating evidence has recently documented that SIRT3 is associated with many types of human diseases, including age-related diseases, cancer, heart disease and metabolic diseases, indicating that SIRT3 can be a potential therapeutic target. Here we focus on summarizing the intricate mechanisms of SIRT3 in human diseases, and recent notable advances in the field of small-molecule activators or inhibitors targeting SIRT3 as well as their potential therapeutic applications for future drug discovery.