Caspase Inhibition Prevents Tumor Necrosis Factor-α-Induced Apoptosis and Promotes Necrotic Cell Death in Mouse Hepatocytes in Vivo and in Vitro

The Ways to Die: Cell Death in Liver Pathophysiology

Liver diseases are closely associated with various cell death mechanisms, including apoptosis, necroptosis, autophagy, pyroptosis, and ferroptosis. Each process contributes uniquely to the pathophysiology of liver injury and repair. Importantly, these mechanisms are not limited to hepatocytes; they also significantly involve nonparenchymal cells. This review examines the molecular pathways and regulatory mechanisms underlying these forms of cell death in hepatocytes, emphasizing their roles in several liver diseases, such as ischemia-reperfusion injury, metabolic dysfunction-associated steatotic liver disease, drug-induced liver injury, and alcohol-associated liver disease. Recent insights into ferroptosis and pyroptosis may reveal novel therapeutic targets for managing liver diseases. This review aims to provide a comprehensive overview of these cell death mechanisms in the context of liver diseases, detailing their molecular signaling pathways and implications for potential treatment strategies.

Converting suspension-type human primary hepatocytes to be plateable-type for use as an in vitro pharmacokinetics model

Preclinical animal models cannot precisely predict medication failures in clinical trials. Human primary hepatocytes (HPHs) are the gold standard for in vitro culture systems that recapitulate in vivo human liver characteristics. Consequently, demand for HPHs is rising despite their high cost, batch-to-batch variability, and inadequate supply. Existing commercial HPHs are plateable (pHPHs) and suspension (sHPHs) using same isolation and cryopreservation technique. The sHPHs cannot be cultured on the plate surface or cannot efficiently relocalize efflux transporters. They can also have a life of maximum of 2-4 h. Therefore, they are unsuitable for assays requiring well-organized efflux transporters or long-term studies, such as enzyme induction or metabolic assays for low-turnover drugs. We aim to develop a novel pharmacokinetic model of converted sHPHs to be attached like pHPHs. We successfully cultured sHPHs as 2D sandwich-cultured sHPHs for use as a promising, reproducible, and affordable in vitro model for efflux trans-porter assays, cytochrome P450 induction, and metabolic studies. The sHPHs successfully attached, converted to be plateable, similar morphology, and mRNA expression as pHPHs, as well as detectable metabolic activity and extended lifespan. Overall, this study is the first to culture functional 2D sandwich sHPHs as a novel in vitro pharmacokinetic model.

Mechanistic Understanding of Dexamethasone-Mediated Protection against Remdesivir-Induced Hepatotoxicity

Remdesivir (RDV), a broad-spectrum antiviral agent, is often used together with dexamethasone (DEX) for hospitalized COVID-19 patients requiring respiratory support. Potential hepatic adverse drug reaction is a safety concern associated with the use of RDV. We previously reported that DEX cotreatment effectively mitigates RDV-induced hepatotoxicity and reduces elevated serum alanine aminotransferase and aspartate aminotransferase levels in cultured human primary hepatocytes (HPH) and hospitalized COVID-19 patients, respectively. Yet, the precise mechanism behind this protective drug-drug interaction remains largely unknown. Here, we show that through the activation of p38, c-Jun N-terminal kinase (JNK), and extracellular signal-regulated kinases 1 and 2 (ERK1/2) signaling, RDV induces apoptosis (cleavage of caspases 8, 9, and 3), autophagy (increased autophagosome and LC3-II), and mitochondrial damages (decreased membrane potential, respiration, ATP levels, and increased expression of Bax and the released cytosolic cytochrome C) in HPH. Importantly, cotreatment with DEX partially reversed RDV-induced apoptosis, autophagy, and cell death. Mechanistically, DEX deactivates/dephosphorylates p38, JNK, and ERK1/2 signaling by enhancing the expression of dual specificity protein phosphatase 1 (DUSP1), a mitogen-activated protein kinase (MAPK) phosphatase, in a glucocorticoid receptor (GR)-dependent manner. Knockdown of GR in HPH attenuates DEX-mediated DUSP1 induction, MAPK dephosphorylation, as well as protection against RDV-induced hepatotoxicity. Collectively, our findings suggest a molecular mechanism by which DEX modulates the GR-DUSP1-MAPK regulatory axis to alleviate the adverse actions of RDV in the liver. SIGNIFICANCE STATEMENT: The research uncovers the molecular mechanisms by which dexamethasone safeguards against remdesivir-associated liver damage in the context of COVID-19 treatment.

The mitochondrial genome-encoded peptide MOTS-c interacts with Bcl-2 to alleviate nonalcoholic steatohepatitis progression

Nonalcoholic steatohepatitis (NASH) is a metabolism-associated fatty liver disease with accumulated mitochondrial stress, and targeting mitochondrial function is a potential therapy. The mitochondrial genome-encoded bioactive peptide MOTS-c plays broad physiological roles, but its effectiveness and direct targets in NASH treatment are still unclear. Here, we show that long-term preventive and short-term therapeutic effects of MOTS-c treatments alleviate NASH-diet-induced liver steatosis, cellular apoptosis, inflammation, and fibrosis. Mitochondrial oxidative capacity and metabolites profiling analysis show that MOTS-c significantly reverses NASH-induced mitochondrial metabolic deficiency. Moreover, we identify that MOTS-c directly interacts with the BH3 domain of antiapoptotic B cell lymphoma-2 (Bcl-2), increases Bcl-2 protein stability, and suppresses Bcl-2 ubiquitination. By using a Bcl-2 inhibitor or adeno-associated virus (AAV)-mediated Bcl-2 knockdown, we further confirm that MOTS-c improves NASH-induced mitochondrial dysfunction, inflammation, and fibrosis, which are dependent on Bcl-2 function. Therefore, our findings show that MOTS-c is a potential therapeutic agent to inhibit the progression of NASH.

The role of hepatocyte mitochondrial DNA in liver injury

Hepatocytes, the predominant cellular constituents of the liver, exhibit the highest mitochondrial density within the human body. Remarkably, experimental insights from the latter part of the previous century involving extracellular injection of mitochondrial DNA (mtDNA) elucidated its potential to incite autoimmune disorders. Consequently, in instances of liver injury, the substantial release of mtDNA has the potential to trigger the activation of the innate immune response, thereby inducing sustained pathogenic consequences within the organism. This article provides a comprehensive retrospective analysis of recent literature pertaining to the impact of mtDNA release on various hepatic cell populations, elucidating its role and potential mechanisms in liver injury. The findings underscore the central role of mtDNA in modulating the immune system, primarily through the orchestration of a cytokine storm, further exacerbating the occurrence of liver injury.

Network pharmacology, a promising approach to reveal the pharmacology mechanism of Chinese medicine formula

ETHNOPHARMACOLOGICAL RELEVANCE

Network pharmacology is a new discipline based on systems biology theory, biological system network analysis, and multi-target drug molecule design specific signal node selection. The mechanism of action of TCM formula has the characteristics of multiple targets and levels. The mechanism is similar to the integrity, systematization and comprehensiveness of network pharmacology, so network pharmacology is suitable for the study of the pharmacological mechanism of Chinese medicine compounds.

AIM OF THE STUDY

The paper summarizes the present application status and existing problems of network pharmacology in the field of Chinese medicine formula, and formulates the research ideas, up-to-date key technology and application method and strategy of network pharmacology. Its purpose is to provide guidance and reference for using network pharmacology to reveal the modern scientific connotation of Chinese medicine.

MATERIALS AND METHODS

Literatures in this review were searched in PubMed, China National Knowledge Infrastructure (CNKI), Web of Science, ScienceDirect and Google Scholar using the keywords "traditional Chinese medicine", "Chinese herb medicine" and "network pharmacology". The literature cited in this review dates from 2002 to 2022.

RESULTS

Using network pharmacology methods to predict the basis and mechanism of pharmacodynamic substances of traditional Chinese medicines has become a trend.

CONCLUSION

Network pharmacology is a promising approach to reveal the pharmacology mechanism of Chinese medicine formula.

Apoptotic cell death in disease-Current understanding of the NCCD 2023

Apoptosis is a form of regulated cell death (RCD) that involves proteases of the caspase family. Pharmacological and genetic strategies that experimentally inhibit or delay apoptosis in mammalian systems have elucidated the key contribution of this process not only to (post-)embryonic development and adult tissue homeostasis, but also to the etiology of multiple human disorders. Consistent with this notion, while defects in the molecular machinery for apoptotic cell death impair organismal development and promote oncogenesis, the unwarranted activation of apoptosis promotes cell loss and tissue damage in the context of various neurological, cardiovascular, renal, hepatic, infectious, neoplastic and inflammatory conditions. Here, the Nomenclature Committee on Cell Death (NCCD) gathered to critically summarize an abundant pre-clinical literature mechanistically linking the core apoptotic apparatus to organismal homeostasis in the context of disease.

A comparative study between angiotensin receptor neprilysin inhibitor (thiorphan/irbesartan) with each of nitrate and carvedilol in a rat model of myocardial ischemic reperfusion injury

The combined angiotensin receptor neprilysin inhibitor is a promising cardioprotective pharmacological agent. This study investigated the beneficial effects of thiorphan (TH)/irbesartan (IRB), in myocardial ischemia-reperfusion (IR) injury, compared to each of nitroglycerin and carvedilol. Male Wistar rats were divided into five groups (10 rats/group): Sham, untreated I/R, TH/IRB + IR (0.1/10 mg/kg), nitroglycerin + IR (0.2 mg/kg), and carvedilol + IR (10 mg/kg). Mean arterial blood pressure, cardiac functions and arrhythmia incidence, duration and score were assessed. Cardiac levels of creatine kinase-MB (CK-MB), oxidative stress, endothelin-1, ATP, Na⁺ /K⁺ ATPase pump activity and mitochondria complexes activities were measured. Histopathological examination, Bcl/Bax immunohistochemistry studies and electron microscopy examination of left ventricle were performed. TH/IRB preserved the cardiac functions and mitochondrial complexes activities, mitigated cardiac damage, reduced oxidative stress and arrhythmia severity, improved the histopathological changes and decreased cardiac apoptosis. TH/IRB showed a comparable effect to each of nitroglycerin and carvedilol in alleviating the IR injury consequences. TH/IRB showed significant preservation of mitochondrial complexes activity I and II compared to nitroglycerin. TH/IRB significantly increased LVdP/dtmax and decreased oxidative stress, cardiac damage and endothelin-1 along with increasing the ATP content, Na⁺ /K⁺ ATPase pump activity and mitochondrial complexes activity when compared to carvedilol. TH/IRB showed a cardioprotective effect in reducing IR injury that is comparable to each of nitroglycerin and carvedilol that could be explained in part by its ability to preserve mitochondrial function, increase ATP, decrease oxidative stress as well as endothelin 1.

Angiotensin receptor-neprilysin inhibitor (thiorphan/irbesartan) improved cardiac function in a rat model of myocardial ischemic reperfusion injury

Mitochondria-mediated apoptosis plays a critical role in myocardial ischemia reperfusion (IR) injury and causes a negative impact on cardiac efficiency and function. The combined angiotensin receptor-neprilysin inhibitor (ARNI) is a promising cardioprotective pharmacological agent that could rescue the heart from IR injury. This study investigated the cardioprotective effect of thiorphan (TH) in combination with three different doses of irbesartan (IRB) on myocardial IR injury and detected the most effective dose combination. Male Wistar rats were used and divided into five groups (10 rats/group): (I) Sham, (II) ischemia-reperfusion I/R, (III) TH/IRB + IR (0.1/5 mg/kg), (IV) TH/IRB + IR (0.1/10 mg/kg), and (V) TH/IRB + IR (0.1/15 mg/kg) groups. Thiorphan and irbesartan were injected intraperitoneally 15 min before IR induction. Mean arterial blood pressure, left ventricular end diastolic pressure (LVEDP), left ventricular maximum rate of pressure (LVdp/dt_max ), and cardiac levels of creatine kinase-MB, malondialdehyde, superoxide dismutase, and endothelin-1 were measured. Cardiac mitochondria complexes activities, histopathological examination of myocardial tissues, immunohistochemistry studies for myocardial apoptosis (Bax and Bcl-2), and electron microscopy examination of left ventricle were performed. TH/IRB combination preserved cardiac functions and mitochondria complex activities and mitigated cardiac damage, oxidative stress, and apoptosis following IR. Also, there was an evident improvement in histopathological changes and electron microscopy examination of left ventricle compared with I/R group. TH/IRB in a dose of 0.1/10 mg/kg showed significant improvement compared with the other treated groups. Thiorphan/irbesartan improved cardiac functions following IR injury. This could be explained by the reported improvement of mitochondria complex activities and reduction of oxidative stress, endothelin-1, and apoptosis.

E-prostanoid 3 receptor deficiency on myeloid cells protects against ischemic acute kidney injury via breaking the auto-amplification loop of necroinflammation

Necroinflammation plays an important role in disease settings such as acute kidney injury (AKI). We and others have elucidated that prostaglandins, which are critically involved in inflammation, may activate E-prostanoid 3 receptor (EP3) at low concentrations. However, how EP3 blockade interacts with regulated cell death and affects AKI remains unknown. In this study, AKI was induced by ischemia-reperfusion (30 minutes/24 hours) in Ep3 knockout (Ep3-/-), bone marrow chimeric, myeloid conditional EP3 knockout and corresponding control mice. The production of prostaglandins E2 and I2 was markedly increased after ischemia-reperfusion, and either abrogation or antagonism of EP3 ameliorated the injury. EP3 deficiency curbed inflammatory cytokine release, neutrophil infiltration and serum high-mobility group box 1 levels, but additional TLR4 inhibition with TAK-242 did not offer further protection against the injury and inflammation. The protection of Ep3-/- was predominantly mediated by suppressing Mixed Lineage Kinase domain-Like-dependent necroptosis, resulting from the inhibition of cytokine generation and the switching of cell death modality from necroptosis to apoptosis through caspase-8 up-regulation, in part due to the restraint of IL-6/JAK2/STAT3 signaling. EP3 deficiency failed to further alleviate the injury when necroptosis was inhibited. Ep3-/- in bone marrow-derived cells, particularly that in myeloid cells, protected kidneys to the same extent as that of global EP3 deletion. Thus, our results demonstrate that EP3 deficiency especially that on myeloid cells, ameliorates ischemic AKI via curbing inflammation and breaking the auto-amplification loop of necroinflammation. Hence, EP3 may be a promising target for the prevention and/or treatment of AKI.

New Therapeutics Targeting Arterial Media Calcification: Friend or Foe for Bone Mineralization?

The presence of arterial media calcification, a highly complex and multifactorial disease, puts patients at high risk for developing serious cardiovascular consequences and mortality. Despite the numerous insights into the mechanisms underlying this pathological mineralization process, there is still a lack of effective treatment therapies interfering with the calcification process in the vessel wall. Current anti-calcifying therapeutics may induce detrimental side effects at the level of the bone, as arterial media calcification is regulated in a molecular and cellular similar way as physiological bone mineralization. This especially is a complication in patients with chronic kidney disease and diabetes, who are the prime targets of this pathology, as they already suffer from a disturbed mineral and bone metabolism. This review outlines recent treatment strategies tackling arterial calcification, underlining their potential to influence the bone mineralization process, including targeting vascular cell transdifferentiation, calcification inhibitors and stimulators, vascular smooth muscle cell (VSMC) death and oxidative stress: are they a friend or foe? Furthermore, this review highlights nutritional additives and a targeted, local approach as alternative strategies to combat arterial media calcification. Paving a way for the development of effective and more precise therapeutic approaches without inducing osseous side effects is crucial for this highly prevalent and mortal disease.

The role of MLKL in Hepatic Ischemia-Reperfusion Injury of Alcoholic Steatotic Livers

Alcohol-related liver disease (ALD) and non-alcoholic fatty liver disease (NAFLD) are the primary causes of chronic liver disease in western countries. Liver transplantation is currently one of the most efficient approaches to save patients with liver failure, which is often associated with hepatic ischemia-reperfusion (IR) injury. IR injury is exacerbated by hepatic steatosis, yet the mechanism remains elusive. Necroptosis is a form of regulated cell death mediated by receptor-interacting protein kinase 1 (RIP1), RIP3 and mixed lineage kinase domain-like (MLKL) protein, which has been implicated in the pathogenesis of ALD and NAFLD. Though necroptosis plays an important role in IR injury of high fat diet - induced steatotic livers, the role of necroptosis in IR injury of ethanol - induced steototic livers has not been investigated. In the present study, we used chronic plus binge alcohol (Gao-binge) feeding followed by IR surgery to investigate IR liver injury with ethanol-associated steatosis. We found that the levels of key necroptotic proteins MLKL and RIP3 increased in alcohol-fed mouse livers. Moreover, we observed increased liver injury after IR in control diet-fed mice, which was further exacerbated by alcohol feeding based on serum alanine aminotransferase (ALT) levels and TUNEL staining of necrotic cells. Hepatic neutrophil infiltration also increased in alcohol-fed mice after IR surgery. However, deletion of Mlkl did not protect against IR liver injury in alcohol-fed mice compared with matched wild-type mice. In conclusion, alcoholic steatosis promotes IR injury, which seems to be independent of MLKL-mediated necroptosis.

Lipopolysaccharide/D-galactosamine-induced acute liver injury could be attenuated by dopamine receptor agonist rotigotine via regulating NF-κB signaling pathway

The pathological of lipopolysaccharide (LPS)/D-galactosamine (D-Gal)-induced acute liver injury is similar to what is seen clinically, and be mediated by the release of pro-inflammatory mediators. A growing body of studies have shown that dopamine (DA) and DA receptor agonist are associated with inflammation and immune response. Rotigotine, a non-ergoline dopamine receptor agonist, is a drug for the treatment of Parkinson's disease. Rotigotine-loaded microspheres (RoMS) is an intramuscular extended-release agent, which can steadily release rotigotine for more than 7 days after a single administration. The present study aimed to investigate the effects of rotigotine and RoMS on inflammation and acute liver injury induced by LPS/D-Gal in mice. The LPS/D-Gal-induced liver injury was evidenced by increases of serum aminotransferases activities and liver histological lesions. Pretreatment with rotigotine or RoMS not only ameliorated the liver histologic lesions, but also reduced the activities of serum aminotransferases and the production of TNF-α. It also showed that rotigotine and RoMS increased DA receptor 2 (DRD2) expression in LPS/D-Gal-exposed mice. Rotigotine and RoMS activated β-arrestin 2, inhibited the phosphorylation of Akt, IκB and the transposition of NF-κB. In line with the above findings, the protective effects of rotigotine and RoMS were abrogated by haloperidol, a DA receptor antagonist. In conclusion, dopamine receptor agonist can regulate NF-κB inflammatory signaling pathway and exert protective effects in LPS/D-Gal-induced liver injury.

Vitexin Mitigates Myocardial Ischemia/Reperfusion Injury in Rats by Regulating Mitochondrial Dysfunction via Epac1-Rap1 Signaling

Revascularization is an effective therapy for rescuing myocardial tissue after ischemic events. However, the process of reperfusion can lead to more severe cardiomyocyte damage, called myocardial ischemia-reperfusion (I/R) injury (MIRI). We have previously shown that vitexin (VT) (a flavonoid compound derived from natural products) protects against MIRI; however, the exact mechanisms underpinning this effect require further elucidation. This study is aimed at elucidating the protective mechanism of VT in inhibiting ischemic myocardial mitochondrial dysfunction and reducing cardiomyocyte apoptosis by regulating Epac1-Rap1 signaling. Isolated rat hearts were subjected to MIRI in a Langendorff perfusion system, and H9c2 cells were subjected to hypoxia/reoxygenation (H/R) in vitro. Our analyses show that during I/R, Epac1 expression was upregulated, left ventricular dysfunction deteriorated, mitochondrial dynamics were disrupted, and both myocardial cells and tissues exhibited apoptosis. Furthermore, administration of 8-CPT (an Epac agonist) exacerbated cardiomyocyte injury and mitochondrial dysfunction. Interestingly, suppressing the function of Epac1 through VT or ESI-09 (an Epac inhibitor) treatment during I/R reduced the myocardial infarct size, cardiomyocyte apoptosis, and reactive oxygen species production; alleviated mitochondrial dysfunction by increasing mitochondrial membrane potential; elevated MFN2 expression; and inhibited Drp1 expression. To our knowledge, our results reveal, for the first time, the mechanisms underlying the protective effect of VT in the myocardium of rats with MIRI. Moreover, we provide a new target and theoretical basis for VT in the treatment of ischemic heart disease.

Necroptosis triggered by ROS accumulation and Ca2+ overload, partly explains the inflammatory responses and anti-cancer effects associated with 1Hz, 100 mT ELF-MF in vivo

Whereas the anti-neoplastic activity of extremely low frequency magnetic fields (ELF-EMF) is well-documented in literature, little is known about its underlying anti-cancer mechanisms and induced types of cell death. Here, for the first time, we reported induction of necroptosis, a specific type of programed necrotic cell death, in MC4-L2 breast cancer cell lines following a 2 h/day exposure to a 100 Hz, 1 mT ELF-EMF for five days. For in vivo assessment, inbred BALB/c mice bearing established MC-4L2 tumors were exposed to 100 mT, 1 Hz ELF-EMF 2 h daily for a period of 28-day, following which tumors were dissected and fixed for evaluation of tumor biomarkers expression and types of cell death induced using TUNEL assay, Immunohistochemistry and H&E staining. Peripheral blood samples were also collected for assessing pro-inflammatory cytokine profile following exposure. An exaggerated proinflammatory response evident form enhancement of IFN-γ (4.8 ± 0.24 folds) and TNF-α (3.1 ± 0.19 folds) and number of tumors infiltrating lymphocytes (TILs), specially CD8⁺ T_h cells (~20 folds), proposed occurrence of necroptosis in vivo. Meanwhile, exposure could effectively suppress tumor growth and expression of Ki-67, CD31, VEGFR2 and MMP-9. In vitro studies on ELF-EMF exposed MC-4L2 cells demonstrated a meaningful increase in phosphorylation of RIPK1/RIPK3/MLKL proteins and cleavage of caspase-9/caspase-3, confirming occurrence of both necroptosis and apoptosis. Complementary in vitro studies by treating ELF-EMF exposed MC-4L2 cells with verapamil (a calcium channel inhibitor), N-acetyl cysteine (a ROS scavenger) or calcium chloride confirmed the role of elevated intracellular calcium and ROS levels in ELF-EMF induced necroptosis.

Can carbon nanofibers affect anurofauna? Study involving neotropical Physalaemus cuvieri (Fitzinger, 1826) tadpoles

Although carbon nanotubes' (CNTs) toxicity in different experimental systems (in vivo and in vitro) is known, little is known about the toxic effects of carbon nanofibers (CNFs) on aquatic vertebrates. We herein investigated the potential impact of CNFs (1 and 10 mg/L) by using Physalaemus cuvieri tadpoles as experimental model. CNFs were able to induce nutritional deficit in animals after 48-h exposure to them, and this finding was inferred by reductions observed in body concentrations of total soluble carbohydrates, total proteins, and triglycerides. The increased production of hydrogen peroxide, reactive oxygen species and thiobarbituric acid reactive substances in tadpoles exposed to CNFs has suggested REDOX homeostasis change into oxidative stress. This process was correlated to the largest number of apoptotic and necrotic cells in the blood of these animals. On the other hand, the increased superoxide dismutase and catalase activity has suggested that the antioxidant system of animals exposed to CNFs was not enough to maintain REDOX balance. In addition, CNFs induced increase in acetylcholinesterase and butyrylcholinesterase activity, as well as changes in the number of neuromasts evaluated on body surface (which is indicative of the neurotoxic effect of nanomaterials on the assessed model system). To the best of our knowledge, this is the first report on the impact of CNFs on amphibians; therefore, it broadened our understanding about ecotoxicological risks associated with their dispersion in freshwater ecosystems and possible contribution to the decline in the populations of anurofauna species.

Kupffer Cell-Derived TNF-α Triggers the Apoptosis of Hepatic Stellate Cells through TNF-R1/Caspase 8 due to ER Stress

Purpose

To investigate the roles of ER stress in Kupffer cells (KCs) and KC-derived TNF-α in the apoptosis of hepatic stellate cells (HSCs).

Methods

A rat model of liver fibrosis was established. Liver and blood serum samples were collected. Liver function assays, Masson staining, Sirius Red staining, ELISAs, and TUNEL and immunohistochemical staining were performed. Liver function, liver fibrosis, KC phenotype, inflammatory factors, and number of active HSCs were investigated. KCs were isolated, treated with tunicamycin, and then, cocultured with primary hepatic stellate cells. ELISAs, immunofluorescence staining, flow cytometry, and Western blotting were performed. KC phenotype, inflammatory factors, HSC apoptosis, and TNF-R1/caspase 8 pathway activity were examined.

Result

s. ER stress in KCs reduced the levels of liver function markers, reduced the degree of liver fibrosis, and increased the number of KCs with the M1 phenotype and the expression of TNF-α. The increase in KC-derived TNF-α reduced the number of active HSCs and increased the activity of TNF-R1/caspase 8. Furthermore, ER stress in KCs promoted the polarization of KCs towards the M1 phenotype and increased the expression of TNF-α. The increase in KC-derived TNF-α triggered the apoptosis of HSCs and the activation of TNF-R1/caspase 8 in vitro, which was consistent with the in vivo results.

Conclusion

ER stress in KCs promotes the polarization of these cells towards the M1 phenotype and increases the expression of TNF-α. Then, the increase in KC-derived TNF-α triggers the apoptosis of HSCs through TNF-R1/caspase 8.

Caspase inhibitor z-VAD-FMK increases the survival of hair cells after Actinomycin-D-induced damage in vitro

Actinomycin-D (Act-D) is a highly effective chemotherapeutic agent that induces apoptosis in systemic tissues. Act-D combined with other chemotherapeutic agents exhibits ototoxic effects and causes hearing impairment. To investigate the potential toxic effects of Act-D in the inner ear, we treated cochlear organotypic cultures with varying concentrations of Act-D for different durations. For the first time, we found that Act-D specifically induced HC loss and apoptosis in a dose- and time-dependent manner but not neuronal degeneration. Co-treatment with benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (z-VAD-FMK), a pan cysteine protease inhibitor, significantly reduced HC loss and apoptosis induced by Act-D, indicating increased cell survival. Taken together, Act-D exposure has ototoxic effects on the auditory system, while z-VAD-FMK prevents Act-D-induced hair cell damage.

[Endoplasmic reticulum stress enhances tumor necrosis factor-α expression in rat Kupffer cells to trigger hepatic stellate apoptosis cell through TNFR/caspase-8 pathway]

OBJECTIVE

To investigate the role of endoplasmic reticulum (ER)-stress of Kupffer cells (KCs) and KCs-derived tumor necrosis factor-α (TNF-α) in medicating apoptosis of hepatic stellate cell (HSC).

METHODS

Sixty male SD rats were randomized into control group, model group, ER- stress group, depletion group and KCs block group (n=15). The 4 groups of rats were given intraperitoneal injections (twice a week for 8 weeks) of normal saline (2 mg/kg); 40% CCl4 solution (in peanut oil, 2 mg/kg); 40% CCl4 solution (2 mg/kg) and tunicamycin (1 mg/kg); and 40% CCl4 solution (2 mg/kg) and tunicamycin (1 mg/kg) followed by clodronate liposomes (50 mg/kg), respectively. After the treatments, samples of the liver tissue and serum were collected from the rats from the 4 groups to isolate KC cells, which were co-cultured with LX2 cells. In the depletion group, the rats were injected with anti-rat TNFR mAb (0.35 mg/kg) via the portal vein before isolating the KCs. Liver function examination, Eirius red staining, ELISA, immuno- histochemical staining, and RT-PCR were performed to assess the liver function, liver fibrosis, KC phenotypes, expression of the in fl ammatory factors, and the number of active HSC was detected. The isolated KCs were treated with tunicamycin before co-culture with LX2 cells, and ELISA, RT-PCR and Western blot were performed to examine KC phenotypes, in fl ammatory factors, LX2 cell apoptosis and TNFR/caspase8 pathway activity.

RESULTS

Compared with the rats in the control group, the rats in the model group had significantly increased ALT and AST levels, Sirius red staining-positive area, and Desmin-positive cells (activated HSCs) (P < 0.05) with significantly lowered number of CD16-positive KCs (M1), and TNF-α protein and mRNA expression (P < 0.05). Compared with those in the model group, the rats in ER-stress group showed significantly decreased ALT and AST levels, Sirius red staining positivity and Desmin-positive cells (P < 0.05) and increased number of CD16-positive KCs and TNF-α expressions (P < 0.05). In the depletion group, compared with the ER-stress group, the rats had significantly increased ALT and AST levels of, Sirius red staining positivity and Desmin-positive cells (P < 0.05) and reduced CD16- positive KCs and TNF-αexpressions (P < 0.05). In the cell co-culture experiment, the model group showed significantly reduced TUNEL-positive LX2 cells, CD16-positive cells, and expressions of TNFR1, cleaved caspase- 8 and cleaved caspase- 3 in the KCs (P < 0.05) with increased Desmin-positive LX2 cells (P < 0.05). Compared with the model group, the ER- stress group exhibited significantly increased TUNEL-positive LX2 cells, CD16-positive cells and expressions of TNFR, cleaved caspase-8 and cleaved caspase-3 in the KCs (P < 0.05) and decreased Desmin-positive LX2 cells (P < 0.05). In the depletion group, blocking TNFR resulted in significantly decreased expressions of cleaved caspase-8 and cleaved caspase-3 compared with those in ER- stress group (P < 0.05) although there was no significant changed in TNFR expression.

CONCLUSIONS

ER stress of KCs promotes the transformation of KCs towards M1 phenotype and increases the expression of TNF-α, which triggers the apoptosis of HSCs through the TNFR/caspase-8 pathway.

hnRNPU/TrkB Defines a Chromatin Accessibility Checkpoint for Liver Injury and Nonalcoholic Steatohepatitis Pathogenesis

BACKGROUND AND AIMS

Nonalcoholic steatohepatitis (NASH) is a progressive liver disease that is characterized by liver injury, inflammation, and fibrosis. NASH pathogenesis is linked to reprogramming of chromatin landscape in the liver that predisposes hepatocytes to stress-induced tissue injury. However, the molecular nature of the putative checkpoint that maintains chromatin architecture and preserves hepatocyte health remains elusive.

APPROACH AND RESULTS

Here we show that heterogeneous nuclear ribonucleoprotein U (hnRNPU), a nuclear matrix protein that governs chromatin architecture and gene transcription, is a critical factor that couples chromatin disruption to NASH pathogenesis. RNA-seq and chromatin immunoprecipitation-seq studies revealed an extensive overlap between hnRNPU occupancy and altered gene expression during NASH. Hepatocyte-specific inactivation of hnRNPU disrupted liver chromatin accessibility, activated molecular signature of NASH, and sensitized mice to diet-induced NASH pathogenesis. Mechanistically, hnRNPU deficiency stimulated the expression of a truncated isoform of TrkB (TRKB-T1) that promotes inflammatory signaling in hepatocytes and stress-induced cell death. Brain-derived neurotrophic factor treatment reduced membrane TRKB-T1 protein and protected mice from diet-induced NASH.

CONCLUSIONS

These findings illustrate a mechanism through which disruptions of chromatin architecture drive the emergence of disease-specific signaling patterns that promote liver injury and exacerbate NASH pathogenesis.

Vitexin attenuates myocardial ischemia/reperfusion injury in rats by regulating mitochondrial dysfunction induced by mitochondrial dynamics imbalance

Vitexin (VT) is a main bioactive flavonoid compound derived from the dried leaf of hawthorn (Crataegus pinnatifida), a widely used Chinese traditional folk medicine. Recent studies have shown that vitexin presents cardioprotective effects in vivo and in vitro. Mitochondrial dysfunction is a salient feature of myocardial ischemia/reperfusion (I/R) injury (MIRI), but the potential mechanism is still unclear. This study investigated the cardioprotective effect of vitexin against MIRI and its possible mechanism. Isolated SD rat hearts were subjected to MIRI in a Langendorff perfusion system, and H9c2 cells were subjected to hypoxia/reoxygenation (H/R) in vitro. Ex vivo experiments showed improved left ventricular function and reduced infarct size in the vitexin group. Transmission electron microscopy showed that I/R caused outer mitochondrial membrane rupture, cristae disappearance and vacuolation, while vitexin reduced mitochondrial damage and ultimately reduced cardiomyocyte apoptosis. In vitro, vitexin protected H9c2 cells from H/R-induced mitochondrial dysfunction, significantly reducing ROS levels; improving mitochondrial activity, mitochondrial membrane potential and ATP content; markedly increasing MFN2 expression and reducing the recruitment of Drp1 in mitochondria. These results suggest a new protective mechanism of vitexin for ischemic heart disease treatment.

Impaired TFEB-mediated lysosomal biogenesis promotes the development of pancreatitis in mice and is associated with human pancreatitis

Impaired macroautophagy/autophagy has been implicated in experimental and human pancreatitis. However, the transcriptional control governing the autophagy-lysosomal process in pancreatitis is largely unknown. We investigated the role and mechanisms of TFEB (transcription factor EB), a master regulator of lysosomal biogenesis, in the pathogenesis of experimental pancreatitis. We analyzed autophagic flux, TFEB nuclear translocation, lysosomal biogenesis, inflammation and fibrosis in GFP-LC3 transgenic mice, acinar cell-specific tfeb knockout (KO) and tfeb and tfe3 double-knockout (DKO) mice as well as human pancreatitis samples. We found that cerulein activated MTOR (mechanistic target of rapamycin kinase) and increased the levels of phosphorylated TFEB as well as pancreatic proteasome activities that led to rapid TFEB degradation. As a result, cerulein decreased the number of lysosomes resulting in insufficient autophagy in mouse pancreas. Pharmacological inhibition of MTOR or proteasome partially rescued cerulein-induced TFEB degradation and pancreatic damage. Furthermore, genetic deletion of tfeb specifically in mouse pancreatic acinar cells increased pancreatic edema, necrotic cell death, infiltration of inflammatory cells and fibrosis in pancreas after cerulein treatment. tfeb and tfe3 DKO mice also developed spontaneous pancreatitis with increased pancreatic trypsin activities, edema and infiltration of inflammatory cells. Finally, decreased TFEB nuclear staining was associated with human pancreatitis. In conclusion, our results indicate a critical role of impaired TFEB-mediated lysosomal biogenesis in promoting the pathogenesis of pancreatitis. Abbreviations: AC: acinar cell; AMY: amylase; ATP6V1A: ATPase, H+ transporting, lysosomal V1 subunit A; ATP6V1B2: ATPase, H+ transporting, lysosomal V1 subunit B2; ATP6V1D: ATPase, H+ transporting, lysosomal V1 subunit D; ATP6V1H: ATPase, H+ transporting, lysosomal V1 subunit H; AV: autophagic vacuole; CDE: choline-deficient, ethionine-supplemented; CLEAR: coordinated lysosomal expression and regulation; CQ: chloroquine; EIF4EBP1: eukaryotic translation initiation factor 4E binding protein 1; EM: electron microscopy; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GFP: green fluorescent protein; H & E: hematoxylin and eosin; KO: knockout; LAMP1: lysosomal-associated membrane protein 1; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MAPK1/ERK2: mitogen-activated protein kinase 1; MTORC1: mechanistic target of rapamycin kinase complex 1; ND: normal donor; NEU: neutrophil; PPARGC1A/PGC1α: peroxisome proliferator-activated receptor, gamma, coactivator 1 alpha; RIPA: radio-immunoprecipitation; RPS6: ribosomal protein S6; SQSTM1/p62: sequestosome 1; TFEB: transcription factor EB; TM: tamoxifen; WT: wild-type; ZG: zymogen granule.

Endoplasmic Reticulum Stress Activates Unfolded Protein Response Signaling and Mediates Inflammation, Obesity, and Cardiac Dysfunction: Therapeutic and Molecular Approach

Obesity has been implicated as a risk factor for insulin resistance and cardiovascular diseases (CVDs). Although the association between obesity and CVD is a well-established phenomenon, the precise mechanisms remain incompletely understood. This has led to a relative paucity of therapeutic measures for the prevention and treatment of CVD and associated metabolic disorders. Recent studies have shed light on the pivotal role of prolonged endoplasmic reticulum stress (ERS)-initiated activation of the unfolded protein response (UPR), the ensuing chronic low-grade inflammation, and altered insulin signaling in promoting obesity-compromised cardiovascular system (CVS). In this aspect, potential ways of attenuating ERS-initiated UPR signaling seem a promising avenue for therapeutic interventions. We review intersecting role of obesity-induced ERS, chronic inflammation, insulin resistance, and oxidative stress in the discovery of targeted therapy. Moreover, this review highlights the current progress and strategies on therapeutics being explored in preclinical and clinical research to modulate ERS and UPR signaling.

A Comprehensive Review of Autophagy and Its Various Roles in Infectious, Non-Infectious, and Lifestyle Diseases: Current Knowledge and Prospects for Disease Prevention, Novel Drug Design, and Therapy

Autophagy (self-eating) is a conserved cellular degradation process that plays important roles in maintaining homeostasis and preventing nutritional, metabolic, and infection-mediated stresses. Autophagy dysfunction can have various pathological consequences, including tumor progression, pathogen hyper-virulence, and neurodegeneration. This review describes the mechanisms of autophagy and its associations with other cell death mechanisms, including apoptosis, necrosis, necroptosis, and autosis. Autophagy has both positive and negative roles in infection, cancer, neural development, metabolism, cardiovascular health, immunity, and iron homeostasis. Genetic defects in autophagy can have pathological consequences, such as static childhood encephalopathy with neurodegeneration in adulthood, Crohn's disease, hereditary spastic paraparesis, Danon disease, X-linked myopathy with excessive autophagy, and sporadic inclusion body myositis. Further studies on the process of autophagy in different microbial infections could help to design and develop novel therapeutic strategies against important pathogenic microbes. This review on the progress and prospects of autophagy research describes various activators and suppressors, which could be used to design novel intervention strategies against numerous diseases and develop therapeutic drugs to protect human and animal health.

Necroptotic Cell Death in Liver Transplantation and Underlying Diseases: Mechanisms and Clinical Perspective

Cell death is a natural process for the turnover of aged cells, but it can also arise as a result of pathological conditions. Cell death is recognized as a key feature in both acute and chronic hepatobiliary diseases caused by drug, alcohol, and fat uptake; by viral infection; or after surgical intervention. In the case of chronic disease, cell death can lead to (chronic) secondary inflammation, cirrhosis, and the progression to liver cancer. In liver transplantation, graft preservation and ischemia/reperfusion injury are associated with acute cell death. In both cases, so-called programmed cell death modalities are involved. Several distinct types of programmed cell death have been described of which apoptosis and necroptosis are the most well known. Parenchymal liver cells, including hepatocytes and cholangiocytes, are susceptible to both apoptosis and necroptosis, which are triggered by distinct signal transduction pathways. Apoptosis is dependent on a proteolytic cascade of caspase enzymes, whereas necroptosis induction is caspase-independent. Moreover, different from the "silent" apoptotic cell death, necroptosis can cause a secondary inflammatory cascade, so-called necroinflammation, triggered by the release of various damage-associated molecular patterns (DAMPs). These DAMPs activate the innate immune system, leading to both local and systemic inflammatory responses, which can even cause remote organ failure. Therapeutic targeting of necroptosis by pharmacological inhibitors, such as necrostatin-1, shows variable effects in different disease models.

Receptor-Interacting Serine/Threonine-Protein Kinase 3 (RIPK3)-Mixed Lineage Kinase Domain-Like Protein (MLKL)-Mediated Necroptosis Contributes to Ischemia-Reperfusion Injury of Steatotic Livers

Increased hepatic ischemia-reperfusion (IR) injury in steatotic livers is a major reason for rejecting the use of fatty livers for liver transplantation. Necroptosis is implicated in the pathogenesis of fatty liver diseases. Necroptosis is regulated by three key proteins: receptor-interacting serine/threonine-protein kinase (RIPK)-1, RIPK3, and mixed-lineage kinase domain-like protein (MLKL). Here, we found that marked steatosis of the liver was induced when a Western diet was given in mice; steatosis was associated with the inhibition of hepatic proteasome activities and with increased levels of key necroptosis-related proteins. Mice fed a Western diet had more severe liver injury, as demonstrated by increases in serum alanine aminotransferase and necrotic areas of liver, after IR than did mice fed a control diet. Although hepatic steatosis was not different between Mlkl knockout mice and wild-type mice, Mlkl knockout mice had decreased hepatic neutrophil infiltration and inflammation and were protected from hepatic IR injury, irrespective of diet. Intriguingly, Ripk3 knockout or Ripk3 kinase-dead knock-in mice were protected against IR injury at the late phase but not the early phase, irrespective of diet. Overall, our findings indicate that liver steatosis exacerbates hepatic IR injury via increased MLKL-mediated necroptosis. Targeting MLKL-mediated necroptosis may help to improve outcomes in steatotic liver transplantation.

FADD-deficient mouse embryonic fibroblasts undergo RIPK1-dependent apoptosis and autophagy after NB-UVB irradiation

Sun or therapy-related ultraviolet B (UVB) irradiation induces different cell death modalities such as apoptosis, necrosis/necroptosis and autophagy. Understanding of mechanisms implicated in regulation and execution of cell death program is imperative for prevention and treatment of skin diseases. An essential component of death-inducing complex is Fas-associated protein with death domain (FADD), involved in conduction of death signals of different death modalities. The purpose of this study was to enlighten the role of FADD in the selection of cell death mode after narrow-band UVB (NB-UVB) irradiation using specific cell death inhibitors (carbobenzoxy-valyl-alanyl-aspartyl-[O-methyl]- fluoromethylketone (zVAD-fmk), Necrostatin-1 and 3-Methyladenine) and FADD-deficient (FADD^-/-) mouse embryonic fibroblasts (MEFs) and their wild type (wt) counterparts. The results imply that lack of FADD sensitized MEFs to induction of receptor-interacting protein 1 (RIPK1)-dependent apoptosis by the generation of reactive oxygen species (ROS), but without activation of the proteins p53, Bax and Bcl-2 as well as without the enrolment of calpain-2. Autophagy was established as a contributing factor to NB-UVB-induced death execution. By contrast, wt cells triggered intrinsic apoptotic pathway that was resistant to the inhibition by zVAD-fmk and Necrostatin-1 pointing to the mechanism overcoming the cell survival. These findings support the role of FADD in prevention of autophagy-dependent apoptosis.

Senecavirus A 3C Protease Mediates Host Cell Apoptosis Late in Infection

Senecavirus A (SVA), an oncolytic picornavirus used for cancer treatment in humans, has recently emerged as a vesicular disease (VD)-causing agent in swine worldwide. Notably, SVA-induced VD is indistinguishable from foot-and-mouth disease (FMD) and other high-consequence VDs of pigs. Here we investigated the role of apoptosis on infection and replication of SVA. Given the critical role of the nuclear factor-kappa B (NF-κB) signaling pathway on modulation of cell death, we first assessed activation of NF-κB during SVA infection. Results here show that while early during infection SVA induces activation of NF-κB, as evidenced by nuclear translocation of NF-κB-p65 and NF-κB-mediated transcription, late in infection a cleaved product corresponding to the C-terminus of NF-κB-p65 is detected in infected cells, resulting in lower NF-κB transcriptional activity. Additionally, we assessed the potential role of SVA 3C protease (3Cpro) in SVA-induced host-cell apoptosis and cleavage of NF-κB-p65. Transient expression of SVA 3Cpro was associated with cleavage of NF-κB-p65 and Poly (ADP-ribose) polymerase (PARP), suggesting its involvement in virus-induced apoptosis. Most importantly, we showed that while cleavage of NF-κB-p65 is secondary to caspase activation, the proteolytic activity of SVA 3Cpro is essential for induction of apoptosis. Experiments using the pan-caspase inhibitor Z-VAD-FMK confirmed the relevance of late apoptosis for SVA infection, indicating that SVA induces apoptosis, presumably, as a mechanism to facilitate virus release and/or spread from infected cells. Together, these results suggest an important role of apoptosis for SVA infection biology.

Caspase Inhibition Reduces Hepatic Tissue Factor-Driven Coagulation In Vitro and In Vivo

Tissue factor (TF) is the primary activator of the blood coagulation cascade. Liver parenchymal cells (ie, hepatocytes) express TF in a molecular state that lacks procoagulant activity. Hepatocyte apoptosis is an important feature of acute and chronic liver diseases, and Fas-induced apoptosis increases hepatocyte TF procoagulant activity in vitro. We determined the impact of a pan-caspase inhibitor, IDN-7314, on hepatocyte TF activity in vitro and TF-mediated coagulation in vivo. Treatment of primary mouse hepatocytes with the Fas death receptor ligand (Jo2, 0.5 μg/ml) for 8 h increased hepatocyte TF procoagulant activity and caused release of TF-positive microvesicles. Pretreatment with 100 nM IDN-7314 abolished Jo2-induced caspase-3/7 activity and significantly reduced hepatocyte TF procoagulant activity and release of TF-positive microvesicles. Treatment of wild-type C57BL/6 mice with a sublethal dose of Jo2 (0.35 mg/kg) for 4.5 h increased coagulation, measured by a significant increase in plasma thrombin-antithrombin and TF-positive microvesicles. Total plasma microvesicle-associated TF activity was reduced in mice lacking hepatocyte TF; suggesting TF-positive microvesicles are released from the apoptotic liver. Fibrin(ogen) deposition increased in livers of Jo2-treated wild-type mice and colocalized primarily with cleaved caspase-3-positive hepatocytes. Pretreatment with IDN-7314 reduced caspase-3 activation, prevented the procoagulant changes in Jo2-treated mice, and reduced hepatocellular injury. Overall, the results indicate a central role for caspase activity in TF-mediated activation of coagulation following apoptotic liver injury. Moreover, the results suggest that liver-selective caspase inhibition may be a putative strategy to limit procoagulant and prothrombotic changes in patients with chronic liver disease.

Advances in therapeutic options for portal hypertension

Portal hypertension represents one of the major clinical consequences of chronic liver disease, having a deep impact on patients' prognosis and survival. Its pathophysiology defines a pathological increase in the intrahepatic vascular resistance as the primary factor in its development, being subsequently aggravated by a paradoxical increase in portal blood inflow. Although extensive preclinical and clinical research in the field has been developed in recent decades, no effective treatment targeting its primary mechanism has been defined. The present review critically summarizes the current knowledge in portal hypertension therapeutics, focusing on those strategies driven by the disease pathophysiology and underlying cellular mechanisms.

Tear Luminex Analysis in Dry Eye Patients

Background

The purpose of this study was to analyze tear inflammatory cytokines of different subclasses of dry eye disease (DED) patients using Luminex technology.

Material/Methods

Forty-five DED patients including 20 Sjogren syndrome aqueous tear deficiency (SS-ATD) patients, 20 non-Sjogren syndrome aqueous tear deficiency (NSS-ATD) patients, 15 meibomian gland dysfunction (MGD) patients, and 15 normal participants were enrolled in this study. Concentrations of 11 inflammatory cytokines in tear samples of study participants were measured by Luminex assay; ELISA assay was further applied for validation.

Results

The levels of cytokines were mostly increased (TNF-α, IL-1α, IL-1β, IL-6, IL-8, IL-12P70, IL-13, IFN-γ, and MIP-1α) in DED patients compared with normal participants. And the levels of TNF-α, IL-6, IL-8, and IL-12P70 were significantly elevated in tears of the patient groups compared to tears of participants in the normal group (P<0.05). Statistical differences were also observed among the patient groups (SS-ATD, NSS-ATD, and MGD) for the level of IL-8 and TNF-α. The results of ELISA assay demonstrated the consistence with Luminex assay, confirming the practicality of Luminex technology for the analysis of multiple cytokines in DED patient tears.

Conclusions

The levels of inflammatory cytokines were mostly elevated in DED patients, and statistical differences of some cytokines were also found between SS-ATD, NSS-ATD, and MGD groups, suggesting that inflammatory cytokines could be potential supplements for the diagnosis of DED subclasses and therapeutic targets for DED patients.

Modulation of the Immune System for the Treatment of Glaucoma

Background:

At present intraocular pressure (IOP) lowering therapies are the only approach to treat glaucoma. Neuroprotective strategies to protect the retinal ganglion cells (RGC) from apoptosis are lacking to date. Substantial amount of research concerning the role of the immune system in glaucoma has been performed in the recent years. This review aims to analyse changes found in the peripheral immune system, as well as selected local changes of retina immune cells in the glaucomatous retina.

Methods:

By dividing the immune system into the innate and the adaptive immune system, a systematic literature research was performed to find recent approaches concerning the modulation of the immune system in the context of glaucoma. Also ClinicalTrials.gov was assessed to identify studies with a translational context.

Results:

We found that some aspects of the immune system, such as changes in antibody levels, changes in toll like receptor signalling, T cells and retinal microglial cells, experience more research activity than other areas such as changes in dendritic cells or macrophages. Briefly, results from clinical studies revealed altered immunoreactivities against retinal and optic nerve antigens in sera and aqueous humor of glaucoma patients and point toward an autoimmune involvement in glaucomatous neurodegeneration and RGC death. IgG accumulations along with plasma cells were found localised in human glaucomatous retinae in a pro-inflammatory environment possibly maintained by microglia. Animal studies show that antibodies (e.g. anti- heat shock protein 60 and anti-myelin basic protein) elevated in glaucoma patients provoke autoaggressive RGC loss and are associated with IgG depositions and increased microglial cells. Also, studies addressing changes in T lymphocytes, macrophages but also local immune responses in the retina have been performed and also hold promising results.

Conclusions:

This recapitulation of recent literature demonstrates that the immune system definitely plays a role in the pathogenesis of glaucoma. Multiple changes in the peripheral innate as well as adaptive immune system have been detected and give room for further research concerning valuable therapeutic targets. We conclude that there still is a great need to bring together the results derived from basic research analysing different aspects of the immune system in glaucoma to understand the immune context of the disease. Furthermore local immune changes in the retina of glaucoma patients still leave room for further therapeutic targets

Comparing the effects of different cell death programs in tumor progression and immunotherapy

Our conception of programmed cell death has expanded beyond apoptosis to encompass additional forms of cell suicide, including necroptosis and pyroptosis; these cell death modalities are notable for their diverse and emerging roles in engaging the immune system. Concurrently, treatments that activate the immune system to combat cancer have achieved remarkable success in the clinic. These two scientific narratives converge to provide new perspectives on the role of programmed cell death in cancer therapy. This review focuses on our current understanding of the relationship between apoptosis and antitumor immune responses and the emerging evidence that induction of alternate death pathways such as necroptosis could improve therapeutic outcomes.

Non-apoptotic Caspase regulation of stem cell properties

The evolutionarily conserved family of proteins called caspases are the main factors mediating the orchestrated programme of cell suicide known as apoptosis. Since this protein family was associated with this essential biological function, the majority of scientific efforts were focused towards understanding their molecular activation and function during cell death. However, an emerging body of evidence has highlighted a repertoire of non-lethal roles within a large variety of cell types, including stem cells. Here we intend to provide a comprehensive overview of the key role of caspases as regulators of stem cell properties. Finally, we briefly discuss the possible pathological consequences of caspase malfunction in stem cells, and the therapeutic potential of caspase regulation applied to this context.

RIPK1-RIPK3-MLKL-Associated Necroptosis Drives Leishmania infantum Killing in Neutrophils

Necroptosis is a pro-inflammatory cell death, which happens in the context of caspase-8 inhibition, allowing activation of the receptor interacting protein kinase 1-receptor interacting protein kinase 3-mixed lineage kinase domain-like (RIPK1-RIPK3-MLKL) axis. Recently, necroptosis has emerged as a key component of resistance against pathogens including infected macrophage by Leishmania infantum, the ethiologic agent of Visceral leishmaniasis (VL). VL is the most severe form of Leishmaniasis, characterized by systemic inflammation and neutropenia. However, the role of neutrophil cell death in VL has not been characterized. Here, we showed that VL patients exhibited increased lactate dehydrogenase levels in the serum, a hallmark of cell death and tissue damage. We investigated the effect of necroptosis in neutrophil infection in vitro. Human neutrophils pretreated with zVAD-fmk (pan-caspase inhibitor) and zIETD-fmk (caspase-8 inhibitor) increased reactive oxygen species (ROS) level in response to Leishmania infection, which is associated with necroptotic cell death. MLKL, an important effector molecule downstream of necroptosis pathway, was also required for Leishmania killing. Moreover, in absence of caspases-8, murine neutrophils displayed loss of membrane integrity, higher levels of ROS, and decreased L. infantum viability. Pharmacological inhibition of RIPK1 or RIPK3 increased parasite survival when caspase-8 was blocked. Electron microscopy assays revealed morphological features associated with necroptotic death in L. infantum infected-neutrophils pretreated with caspase inhibitor, whereas infected cells pretreated with RIPK1 and RIPK3 inhibitors did not show ultra-structural alterations in membrane integrity and presented viable Leishmania within parasitophorous vacuoles. Taken together, these findings suggest that inhibition of caspase-8 contributes to elimination of L. infantum in neutrophils by triggering necroptosis. Thus, targeting necroptosis may represent a new strategy to control Leishmania replication.

Caspases in metabolic disease and their therapeutic potential

Caspases, a family of cysteine-dependent aspartate-specific proteases, are central to the maintenance of cellular and organismal homoeostasis by functioning as key mediators of the inflammatory response and/or apoptosis. Both metabolic inflammation and apoptosis play a central role in the pathogenesis of metabolic disease such as obesity and the progression of nonalcoholic steatohepatisis (NASH) to more severe liver disease. Obesity and nonalcoholic fatty liver disease (NAFLD) are the leading global health challenges associated with the development of numerous comorbidities including insulin resistance, type-2 diabetes and early mortality. Despite the high prevalence, current treatment strategies including lifestyle, dietary, pharmaceutical and surgical interventions, are often limited in their efficacy to manage or treat obesity, and there are currently no clinical therapies for NAFLD/NASH. As mediators of inflammation and cell death, caspases are attractive therapeutic targets for the treatment of these metabolic diseases. As such, pan-caspase inhibitors that act by blocking apoptosis have reached phase I/II clinical trials in severe liver disease. However, there is still a lack of knowledge of the specific and differential functions of individual caspases. In addition, cross-talk between alternate cell death pathways is a growing concern for long-term caspase inhibition. Evidence is emerging of the important cell-death-independent, non-apoptotic functions of caspases in metabolic homoeostasis that may be of therapeutic value. Here, we review the current evidence for roles of caspases in metabolic disease and discuss their potential targeting as a therapeutic strategy.

Immune-related proteins detected through iTRAQ-based proteomics analysis of intestines from Apostichopus japonicus in response to tussah immunoreactive substances

Apostichopus japonicus is a species of sea cucumber that is extensively bred as a marine delicacy because of its high nutritive and medicinal value. Immunostimulants are usually used to enhance the immunity of sea cucumber against diseases, but the physiological function of immunostimulants is poorly understood. In this study, we fed A. japonicus individuals with a diet supplemented with different concentrations of tussah immunoreactive substances (TIS), and then subjected their intestines to iTRAQ-based proteomic analysis. A total of 51 differentially expressed proteins were detected in response to TIS, 13 proteins were upregulated, while 38 proteins were reduced. These proteins are involved in phagocytosis, tissue protection, cell apoptosis and energy metabolism. Among these 51 proteins, 7 proteins (GLO2, ACOX, CTTN, MARK, FADD, CSTA and CASP6) related to immunity with functional annotation in sea cucumber were further analyzed. In addition, the upregulated expression of 4 immune-related proteins (GLO2, ACOX, CTTN and MARK) was validated by qRT-PCR. The findings of this study gave further insight into the mechanism by which TIS might enhance the immunity of A. japonicus.

FOXO3-dependent apoptosis limits alcohol-induced liver inflammation by promoting infiltrating macrophage differentiation

Alcohol consumption is generally well tolerated by the liver but in some individuals it results in persistent inflammation and liver disease. The mechanisms that regulate alcohol-induced liver inflammation are poorly understood. The transcription factor FOXO3 has previously been shown to be involved in suppressing alcohol-induced liver injury. In this study we demonstrate that in response to alcohol, approximately 10% of mouse hepatic macrophages undergo FOXO3-dependent apoptosis. By 3 days of alcohol exposure total hepatic macrophage numbers declined by 30% but these were restored to normal after 10 days of continued exposure. Whole body or myeloid specific Foxo3^-/- mice failed to show this apoptotic response. After 10 days of alcohol exposure, Foxo3^−/− mice had an increased basal inflammatory phenotype and an increase in the proportion of pro-inflammatory CD11b⁺, Ly6C⁺ infiltrating macrophages (IMs) infiltrating. This led to marked sensitivity to LPS with a 5-fold ALT elevation and liver injury after LPS challenge in Foxo3^−/− but not WT mice. Restoring the early macrophage apoptosis burst with a pulse of intravenous GdCl₃ at day 2 had no effect on the day 10 phenotype of WT mice but it corrected the hyper-inflammatory phenotype in Foxo3^−/− mice. In conclusion, FOXO3-dependent hepatic macrophage apoptosis in response to ethanol serves to promote differentiation of infiltrating macrophages thus limiting the magnitude of the inflammatory response to ethanol.

In vivo assessment of the hepatotoxicity of a new Nostoc isolate from the Nile River: Nostoc sp. strain NRI

Nostoc sp. is one of the most widely distributed cyanobacterial genera that produce potentially protein phosphatase (PP) inhibitor; microcystins (MCs). MCs have posed a worldwide concern due to predominant hepatotoxicity to human health. We have previously isolated a Nostoc strain (NR1) from the Nile River (the main water supply in Egypt) and this strain exerted production of rare and highly toxic MC; demethylated microcystin-LR. There is no data concerning risk factors of liver diseases for human and animal exposure to NR1-contaminated drinking water yet. It is thus important to evaluate acute (LD₅₀ dose), subacute (0.01% and 10% of LD₅₀ dose) and subchronic (0.01% and 10% of LD₅₀ dose) hepatotoxicity's NR1 extract using experimental mice. Mice groups, who orally received 0.01% LD₅₀, represented a permissible concentration of the World Health Organization (WHO) for MC in drinking water. Several parameters were detected, including hepatotoxicity (i.e. PP activity, liver function, oxidative stress markers and DNA fragmentation), pro-inflammatory cytokine (TNF-α) and liver histopathology. Our results demonstrated LD₅₀ of NR1 extract was at 15,350 mg/kg body weight and caused hepatotoxicity that attributed to PP inhibition and a significant increase of hepatic damage biomarkers with lipid accumulation. Moreover, NR1 extract induced hepatic oxidative damage that may have led to DNA fragmentation and production of TNF-α. As demonstrated from the histopathological study, NR1 extract caused a severe collapse of cytoskeleton with subsequent focal degeneration of hepatocytes, necroinflammation and steatosis. The grade of hepatotoxicity in subacute (10% of LD₅₀) group was higher than that in the subchronic (10% of LD₅₀ and 0.01% of LD₅₀, WHOch, respectively) groups. No significant hepatotoxicity was detectable for subacute (0.01% of LD₅₀, WHOac) group. NR1 is therefore considered as one of the harmful and life-threatening cyanobacteria for Egyptian people being exposed to dose above WHO guideline. Thus, biological indicators and thresholds for water treatment are extremely needed.

AMP-activated protein kinase agonist N6-(3-hydroxyphenyl)adenosine protects against fulminant hepatitis by suppressing inflammation and apoptosis

Both AMP-activated protein kinase (AMPK) agonist and inhibitor have been reported to protect against fulminant hepatitis, implying that AMPK may play a complicated role in the development of fulminant hepatitis. In this study, we exploited whether the novel AMPK agonist N₆-(3-hydroxyphenyl)adenosine (named as M1) exerted protective effects on fulminant hepatitis and whether its beneficial effects were AMPK-dependent. Results showed that intraperitoneal injection of M1 improved liver function, ameliorated liver injury and finally raised the survival rate in d-galactosamine/lipopolysaccharide (GalN/LPS)-treated mice. These beneficial effects of M1 may attribute to the suppression of pro-inflammatory cytokines production and the prevention of hepatocyte apoptosis. Furthermore, M1 pretreatment mitigated LPS-stimulated TLR4 expression and NFκB activation in murine peritoneal macrophages and prevented actinomycin D (Act D)/tumor necrosis factor α (TNFα)-induced apoptosis by promoting protective autophagy in primary hepatocytes. Additionally, M1-induced AMPK activation was responsible both for its anti-inflammatory action in macrophages and for its anti-apoptotic action in hepatocytes. To our surprise, compared with the control AMPKα1^lox/lox/AMPKα2^lox/lox mice, liver-specific AMPKα1 knockout (AMPKα1_LS^−/−) mice were more sensitive to GalN/LPS administration but not AMPKα2_LS^−/−mice, and the beneficial effects of M1 on acute liver failure and the production of pro-inflammatory factors were dampened in AMPKα1_LS^−/− mice. Therefore, our study may prove that M1 could be a promising therapeutic agent for fulminant hepatitis, and targeting AMPK may be useful therapeutically in the control of LPS-induced hepatotoxicity.

Pretreatment with dihydroquercetin, a dietary flavonoid, protected against concanavalin A-induced immunological hepatic injury in mice and TNF-α/ActD-induced apoptosis in HepG2 cells

We have previously demonstrated the hepatoprotective effect of dihydroquercetin (DHQ) against concanavalin A (Con A)-induced immunological hepatic injury in mice.

Hepatic neuregulin 4 signaling defines an endocrine checkpoint for steatosis-to-NASH progression

Nonalcoholic steatohepatitis (NASH) is characterized by progressive liver injury, inflammation, and fibrosis; however, the mechanisms that govern the transition from hepatic steatosis, which is relatively benign, to NASH remain poorly defined. Neuregulin 4 (Nrg4) is an adipose tissue-enriched endocrine factor that elicits beneficial metabolic effects in obesity. Here, we show that Nrg4 is a key component of an endocrine checkpoint that preserves hepatocyte health and counters diet-induced NASH in mice. Nrg4 deficiency accelerated liver injury, fibrosis, inflammation, and cell death in a mouse model of NASH. In contrast, transgenic expression of Nrg4 in adipose tissue alleviated diet-induced NASH. Nrg4 attenuated hepatocyte death in a cell-autonomous manner by blocking ubiquitination and proteasomal degradation of c-FLIPL, a negative regulator of cell death. Adeno-associated virus-mediated (AAV-mediated) rescue of hepatic c-FLIPL expression in Nrg4-deficent mice functionally restored the brake for steatosis to NASH transition. Thus, hepatic Nrg4 signaling serves as an endocrine checkpoint for steatosis-to-NASH progression by activating a cytoprotective pathway to counter stress-induced liver injury.

Stellate Cells Orchestrate Concanavalin A-Induced Acute Liver Damage

Concanavalin A (ConA) causes immune cell-mediated liver damage, but the contribution of resident nonparenchymal cells (NPCs) is also evident. Hepatic stellate cells (HSCs) induce hepatic inflammation and immunological reactions; we therefore investigated their role in ConA-induced liver injury. ConA was administered i.v. to control or HSC-depleted mice; hepatic histopathology and cytokines/chemokines were determined after 6 hours. In vitro, effects of ConA-conditioned HSC medium on hepatocytes were determined. ConA induced inflammation, sinusoidal congestion, and extensive midzonal hepatocyte death in control mice, which were strongly minimized in HSC-depleted mice. CD4 and natural killer T cells and neutrophils were markedly reduced in ConA-treated HSC-depleted mice compared with control mice. The increase in cytokines/chemokines of hepatic injury was much higher in ConA-treated control mice than in HSC-depleted mice. ConA-treated HSCs showed increased expression of interferon-β, tumor necrosis factor-α, and CXCL1, induced oxidative stress in hepatocytes, and caused hepatocyte apoptosis. ConA induced nuclear translocation of interferon-regulatory factor-1 (IRF1) in hepatocytes in vivo, and ConA/HSC induced a similar effect in cultured hepatocytes. IRF1-knockout mice were resistant to ConA-induced liver damage, and anti-interferon β antibody mitigated ConA/HSC-induced injury. In HSC-NPC co-culture, ConA-induced expression of inflammatory cytokines/chemokines was significantly augmented compared with NPCs alone. HSCs play an essential role in ConA-induced liver injury directly via the interferon-β/IRF1 axis, and by modulating properties of NPCs.

MutY DNA Glycosylase Protects Cells From Tumor Necrosis Factor Alpha-Induced Necroptosis

Numerous studies have implied that mutY DNA glycosylase (MYH) is involved in the repair of post-replicative mispairs and plays a critical role in the base excision repair pathway. Recent in vitro studies have shown that MYH interacts with tumor necrosis factor receptor type 1-associated death domain (TRADD), a key effector protein of tumor necrosis factor receptor-1 (TNFR1) signaling. The association between MYH and TRADD is reversed during tumor necrosis factor alpha (TNF-α)- and camptothecin (CPT)-induced apoptosis, and enhanced during TNF-α-induced survival. After investigating the role of MYH interacts with various proteins following TNF-α stimulation, here, we focus on MYH and TRADD interaction functions in necroptosis and its effects to related proteins. We report that the level of the MYH and TRADD complex was also reduced during necroptosis induced by TNF-α and zVAD-fmk. In particular, we also found that MYH is a biologically important necrosis suppressor. Under combined TNF-α and zVAD-fmk treatment, MYH-deficient cells were induced to enter the necroptosis pathway but primary mouse embryonic fibroblasts (MEFs) were not. Necroptosis in the absence of MYH proceeds via the inactivation of caspase-8, followed by an increase in the formation of the kinase receptor- interacting protein 1 (RIP1)-RIP3 complex. Our results suggested that MYH, which interacts with TRADD, inhibits TNF-α necroptotic signaling. Therefore, MYH inactivation is essential for necroptosis via the downregulation of caspase-8. J. Cell. Biochem. 118: 1827-1838, 2017. © 2017 Wiley Periodicals, Inc.

Inhibition of Drp1 protects against senecionine-induced mitochondria-mediated apoptosis in primary hepatocytes and in mice

Pyrrolizidine alkaloids (PAs) are a group of compounds found in various plants and some of them are widely consumed in the world as herbal medicines and food supplements. PAs are potent hepatotoxins that cause irreversible liver injury in animals and humans. However, the mechanisms by which PAs induce liver injury are not clear. In the present study, we determined the hepatotoxicity and molecular mechanisms of senecionine, one of the most common toxic PAs, in primary cultured mouse and human hepatocytes as well as in mice. We found that senecionine administration increased serum alanine aminotransferase levels in mice. H&E and TUNEL staining of liver tissues revealed increased hemorrhage and hepatocyte apoptosis in liver zone 2 areas. Mechanistically, senecionine induced loss of mitochondrial membrane potential, release of mitochondrial cytochrome c as well as mitochondrial JNK translocation and activation prior to the increased DNA fragmentation and caspase-3 activation in primary cultured mouse and human hepatocytes. SP600125, a specific JNK inhibitor, and ZVAD-fmk, a general caspase inhibitor, alleviated senecionine-induced apoptosis in primary hepatocytes. Interestingly, senecionine also caused marked mitochondria fragmentation in hepatocytes. Pharmacological inhibition of dynamin-related protein1 (Drp1), a protein that is critical to regulate mitochondrial fission, blocked senecionine-induced mitochondrial fragmentation and mitochondrial release of cytochrome c and apoptosis. More importantly, hepatocyte-specific Drp1 knockout mice were resistant to senecionine-induced liver injury due to decreased mitochondrial damage and apoptosis. In conclusion, our results uncovered a novel mechanism of Drp1-mediated mitochondrial fragmentation in senecionine-induced liver injury. Targeting Drp1-mediated mitochondrial fragmentation and apoptosis may be a potential avenue to prevent and treat hepatotoxicity induced by PAs.

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Senecionine induces apoptosis in primary mouse and human hepatocytes as well as in mouse livers.

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Senecionine induces mitochondrial Drp1 translocation, mitochondrial fragmentation, loss of mitochondrial membrane potential and release of mitochondrial cytochrome c in hepatocytes.

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Pharmacological inhibition or genetic deletion of Drp1 protects against senecionine-induced hepatotoxicity.

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Targeting Drp1-mediated mitochondrial fragmentation and apoptosis may be a potential avenue to prevent and treat hepatotoxicity induced by Pyrrolizidine alkaloids.

Upregulation of heat shock protein 70 and the differential protein expression induced by tumor necrosis factor-alpha enhances migration and inhibits apoptosis of hepatocellular carcinoma cell HepG2

Tumor necrosis factor alpha (TNFα) plays diverse roles in liver damage and hepatocarcinogenesis with its multipotent bioactivity. However, the influence of TNFα on protein expression of hepatocellular carcinoma (HCC) is incompletely understood. Therefore, we aimed to investigate the differential protein expression of HCC in response to TNFα stimulus. We observed that HepG2 cell revealed a higher resistance to TNFα-induced apoptosis as compared to the non-tumorigenic hepatocyte THLE-2. By using a label-free quantitative proteomic analysis, we found that 520 proteins were differentially expressed in the HepG2 cells exposed to TNFα, including 211 up-regulated and 309 down-regulated proteins. We further confirmed several proteins with significant expression change (TNFα/control ratio>2.0 or <0.5) by immunoblotting using specific antibodies. We also analyzed the differential expressed proteins using Gene ontology and KEGG annotations, and the results implicated that TNFα might regulate ribosome, spliceosome, antigen processing and presentation, and energy metabolism in HepG2 cells. Moreover, we demonstrated that upregulation of heat shock protein 70 (HSP70) was involved in both the promoted migration and the inhibited apoptosis of HepG2 cells in response to TNFα. Collectively, these findings indicate that TNFα alters protein expression such as HSP70, which triggering specific molecular processes and signaling cascades that promote migration and inhibit apoptosis of HepG2 cells.