Chemical hypoxia induces pro-inflammatory signals in fat-laden hepatocytes and contributes to cellular crosstalk with Kupffer cells through extracellular vesicles

Role and therapeutic perspectives of extracellular vesicles derived from liver and adipose tissue in metabolic dysfunction-associated steatotic liver disease

The global epidemic of metabolic diseases has led to the emergence of metabolic dysfunction-associated steatotic liver disease (MASLD) and metabolic dysfunction-associated steatohepatitis (MASH), which pose a significant threat to human health. Despite recent advances in research on the pathogenesis and treatment of MASLD/MASH, there is still a lack of more effective and targeted therapies. Extracellular vesicles (EVs) discovered in a wide range of tissues and body fluids encapsulate different activated biomolecules and mediate intercellular communication. Recent studies have shown that EVs derived from the liver and adipose tissue (AT) play vital roles in MASLD/MASH pathogenesis and therapeutics, depending on their sources and intervention types. Besides, adipose-derived stem cell (ADSC)-derived EVs appear to be more effective in mitigating MASLD/MASH. This review presents an overview of the definition, extraction strategies, and characterisation of EVs, with a particular focus on the biogenesis and release of exosomes. It also reviews the effects and potential molecular mechanisms of liver- and AT-derived EVs on MASLD/MASH, and emphasises the contribution and clinical therapeutic potential of ADSC-derived EVs. Furthermore, the future perspective of EV therapy in a clinical setting is discussed.

Extracellular vesicles originating from steatotic hepatocytes promote hepatic stellate cell senescence via AKT/mTOR signaling

The prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD) is increasing rapidly due to the obesity epidemic. In the inflammatory stages of MASLD (MASH), activation of hepatic stellate cells (HSCs) leads to initiation and progression of liver fibrosis. Extracellular vesicles (EVs) are released from all cell types and play an important role in intercellular communication. However, the role of EVs released from hepatocytes in the context of MASLD is largely unknown. Therefore, the present study aimed to investigate the role of EVs derived from both normal and steatotic (free fatty acid-treated) hepatocytes on the phenotype of HSCs via the senescence pathway. Primary rat hepatocytes were treated with free fatty acids (FFAs: oleic acid and palmitic acid). EVs were collected by ultracentrifugation. EVs markers and HSCs activation and senescence markers were assessed by Western blot analysis, qPCR and cytochemistry. Reactive oxygen species (ROS) production was assessed by fluorescence assay. RNA profiles of EVs were evaluated by sequencing. We found that EVs from hepatocytes treated with FFAs (FFA-EVs) inhibit collagen type 1 and α-smooth muscle actin expression, increase the production of ROS and the expression of senescence markers (IL-6, IL-1β, p21 and senescence-associated β-galactosidase activity) in early activating HSCs via the AKT-mTOR pathway. Sequencing showed differentially enriched RNA species between the EVs groups. In conclusion, EVs from FFA-treated hepatocytes inhibit HSC activation by inducing senescence via the AKT-mTOR signaling pathway. Determining the components in EVs from steatotic hepatocytes that induce HSC senescence may lead to the identification of novel targets for intervention in the treatment of MASLD in the future.

GO-PEG Represses the Progression of Liver Inflammation via Regulating the M1/M2 Polarization of Kupffer Cells

As a highly promising nanomaterial, exploring the impact of the liver, a vital organ, stands out as a crucial focus in the examination of its biological effects. Kupffer cells (KCs) are one of the first immune cells to contact with exotic-substances in liver. Therefore, this study investigates the immunomodulatory effects and mechanisms of polyethylene glycol-modified graphene oxide (GO-PEG) on KCs. Initial RNA-seq and KEGG pathway analyses reveal the inhibition of the TOLL-like receptor, TNF-α and NOD-like receptor pathways in continually stimulated KCs exposed to GO-PEG. Subsequent biological experiments validate that a 48-hour exposure to GO-PEG alleviates LPS-induced KCs immune activation, characterized by a shift in polarization from M1 to M2. The underlying mechanism involves the absorption of double-stranded RNA/single-stranded RNA, inhibiting the activation of TLR3 and TLR7 in KCs. Employing a Kupffer/AML12 cell co-culture model and animal studies, it is observed that GO-PEG indirectly inhibit oxidative stress, mitochondrial dysfunction, and apoptosis in AML12 cells, partially mitigating systemic inflammation and preserving liver tissue/function. This effect is attributed to the paracrine interaction between KCs and hepatocytes. These findings suggest a meaningful and effective strategy for treating liver inflammation, particularly when combined with anti-inflammatory drugs.

Extracellular Vesicles and Their Correlation with Inflammatory Factors in an Experimental Model of Steatotic Liver Disease Associated with Metabolic Dysfunction

Background/Aims: Extracellular vesicles (EVs) are promising as a biomarker of metabolic dysfunction associated steatotic liver disease (MASLD). The objective is to study EVs and their involvement in MASLD concerning the disease's pathogenesis and progression characteristics. Methods: Male adult Sprague Dawley rats were randomly assigned into two experimental models of MASLD: MASLD-16 and MASLD-28, animals received a choline-deficient high-fat diet (CHFD) and Control-16 and Control-28, animals received a standard diet (SD) for 16 and 28 weeks, respectively. Biological samples from these animal models were used, as well as previously registered variables. EVs from hepatic tissue were characterized using confocal microscopy. EVs were isolated through differential ultracentrifugation from serum and characterized using NanoSight. The data from the EVs were correlated with biochemical, molecular, and histopathological parameters. Results: Liver EVs were identified through the flotillin-1 protein. EVs were isolated from the serum of all groups. There was a decrease of EVs concentration in MASLD-28 in comparison with Control-28 (P < 0.001) and a significant increase in EVs concentration in Control-28 compared with Control-16 (P < 0.001). There was a strong correlation between serum EVs concentration with hepatic gene expression of interleukin (Il)6 (r2 = 0.685, P < 0.05), Il1b (r2 = 0.697, P < 0.05) and tumor necrosis factor-alpha (Tnfa; r2 = 0.636, P < 0.05) in MASLD-16. Moreover, there was a strong correlation between serum EVs size and Il10 in MASLD-28 (r2 = 0.762, P < 0.05). Conclusion: The concentration and size of EVs correlated with inflammatory markers, suggesting their involvement in the systemic circulation, cellular communication, and development and progression of MASLD, demonstrating that EVs have the potential to serve as noninvasive biomarkers for MASLD diagnosis and prognosis.

Exosomes regulate SIRT3-related autophagy by delivering miR-421 to regulate macrophage polarization and participate in OSA-related NAFLD

PURPOSE

To analyze the role of and mechanism underlying obstructive sleep apnea (OSA)-derived exosomes in inducing non-alcoholic fatty liver (NAFLD).

METHODS

The role of OSA-derived exosomes was analyzed in inducing hepatocyte fat accumulation in mice models both in vivo and in vitro.

RESULTS

OSA-derived exosomes caused fat accumulation and macrophage activation in the liver tissue. These exosomes promoted fat accumulation; steatosis was more noticeable in the presence of macrophages. Macrophages could internalize OSA-derived exosomes, which promoted macrophage polarization to the M1 type. Moreover, it inhibited sirtuin-3 (SIRT3)/AMP-activated protein kinase (AMPK) and autophagy and promoted the activation of nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 (NLRP3) inflammasomes. The use of 3-methyladenine (3-MA) to inhibit autophagy blocked NLRP3 inflammasome activation and inhibited the M1 polarization of macrophages. miR-421 targeting inhibited SIRT3 protein expression in the macrophages. miR-421 was significantly increased in OSA-derived exosomes. Additionally, miR-421 levels were increased in OSA + NAFLD mice- and patient-derived exosomes. In the liver tissues of OSA and OSA + NAFLD mice, miR-421 displayed similar co-localization with the macrophages. Intermittent hypoxia-induced hepatocytes deliver miR-421 to the macrophages via exosomes to inhibit SIRT3, thereby participating in macrophage M1 polarization. After OSA and NAFLD modeling in miR-421-/- mice, liver steatosis and M1 polarization were significantly reduced. Additionally, in the case of miR-421 knockout, the inhibitory effects of OSA-derived exosomes on SIRT3 and autophagy were significantly alleviated. Furthermore, their effects on liver steatosis and macrophage M1 polarization were significantly reduced.

CONCLUSIONS

OSA promotes the delivery of miR-421 from the hepatocytes to macrophages. Additionally, it promotes M1 polarization by regulating the SIRT3/AMPK-autophagy pathway, thereby causing NAFLD.

Adipocyte-derived exosomes from obstructive sleep apnoea rats aggravate MASLD by TCONS_00039830/miR-455-3p/Smad2 axis

A correlation exists between obstructive sleep apnoea (OSA) and the severity of metabolic dysfunction-associated steatotic liver disease (MASLD), OSA can induce more severe MASLD. However, the underlying regulatory mechanism between the two is unclear. To this end, this study explored the role and possible molecular mechanisms of adipocyte-derived exosomes under OSA in aggravating MASLD. Through sequencing technology, miR-455-3p was identified as a co-differentially expressed miRNA between the MASLD + OSA and Control groups and between the MASLD + OSA and MASLD groups. Upregulation of TCONS-00039830 and Smad2 and downregulation of miR-455-3p in the MASLD and MASLD + OSA groups were validated in vivo and in vitro. TCONS-00039830, as a differentially expressed LncRNA in exosomes found in the sequencing results, transfection notably downregulated miR-455-3p and upregulated Smad2 in hepatocytes. TCONS_00039830 overexpression increased fat, triglyceride and cholesterol levels, while miR-455-3p overexpression decreased these levels. Furthermore, exosome administration promoted the accumulation of fat, triglyceride and cholesterol, upregulated TCONS_00039830 and Smad2, and downregulated miR-455-3p. Overexpression of miR-455-3p reversed the increased fat accumulation and upregulated TCONS_00039830 and Smad2. In conclusion, OSA-derived exosomes promoted hepatocyte steatosis by regulating TCONS_00039830/miR-455-3p/Smad2 axis, thereby aggravating liver damage in MASLD.

Changes in proteomic cargo of circulating extracellular vesicles in response to lifestyle intervention in adolescents with hepatic steatosis

BACKGROUND

Recent studies suggest that proteomic cargo of extracellular vesicles (EVs) may play a role in metabolic improvements following lifestyle interventions. However, the relationship between changes in liver fat and circulating EV-derived protein cargo following intervention remains unexplored.

METHODS

The study cohort comprised 18 Latino adolescents with obesity and hepatic steatosis (12 males/6 females; average age 13.3 ± 1.2 y) who underwent a six-month lifestyle intervention. EV size distribution and concentration were determined by light scattering intensity; EV protein composition was characterized by liquid chromatography tandem-mass spectrometry.

RESULTS

Average hepatic fat fraction (HFF) decreased 23% by the end of the intervention (12.5% [5.5] to 9.6% [4.9]; P = 0.0077). Mean EV size was smaller post-intervention compared to baseline (120.2 ± 16.4 nm to 128.4 ± 16.5 nm; P = 0.031), although the difference in mean EV concentration (1.1E+09 ± 4.1E+08 particles/mL to 1.1E+09 ± 1.8E+08 particles/mL; P = 0.656)) remained unchanged. A total of 462 proteins were identified by proteomic analysis of plasma-derived EVs from participants pre- and post-intervention, with 113 proteins showing differential abundance (56 higher and 57 lower) between the two timepoints (adj-p <0.05). Pathway analysis revealed enrichment in complement cascade, initial triggering of complement, creation of C4 and C2 activators, and regulation of complement cascade. Hepatocyte-specific EV affinity purification identified 40 proteins with suggestive (p < 0.05) differential abundance between pre- and post-intervention samples.

CONCLUSIONS

Circulating EV-derived proteins, particularly those associated with the complement cascade, may contribute to improvements in liver fat in response to lifestyle intervention.

Non-alcoholic fatty liver disease and sleep disorders

Studies have shown that non-alcoholic fatty liver disease (NAFLD) may be associated with sleep disorders. In order to explore the explicit relationship between the two, we systematically reviewed the effects of sleep disorders, especially obstructive sleep apnea (OSA), on the incidence of NAFLD, and analyzed the possible mechanisms after adjusting for confounding factors. NAFLD is independently associated with sleep disorders. Different sleep disorders may be the cause of the onset and aggravation of NAFLD. An excessive or insufficient sleep duration, poor sleep quality, insomnia, sleep-wake disorders, and OSA may increase the incidence of NAFLD. Despite that some research suggests a unidirectional causal link between the two, specifically, the onset of NAFLD is identified as a result of changes in sleep characteristics, and the reverse relationship does not hold true. Nevertheless, there is still a lack of specific research elucidating the reasons behind the higher risk of developing sleep disorders in individuals with NAFLD. Further research is needed to establish a clear relationship between NAFLD and sleep disorders. This will lay the groundwork for earlier identification of potential patients, which is crucial for earlier monitoring, diagnosis, effective prevention, and treatment of NAFLD.

The role of extracellular vesicles in non-alcoholic steatohepatitis: Emerging mechanisms, potential therapeutics and biomarkers

Non-alcoholic steatohepatitis (NASH), an emerging global healthcare problem, has become the leading cause of liver transplantation in recent decades. No effective therapies in the clinic have been proven due to the incomplete understanding of the pathogenesis of NASH, and further studies are expected to continue to delve into the mechanisms of NASH. Extracellular vesicles (EVs), which are small lipid membrane vesicles carrying proteins, microRNAs and other molecules, have been identified to play a vital role in cell-to-cell communication and are involved in the development and progression of various diseases. In recent years, there has been increasing interest in the role of EVs in NASH. Many studies have revealed that EVs mediate important pathological processes in NASH, and the role of EVs in NASH is distinct and variable depending on their origin cells and target cells. This review outlines the emerging mechanisms of EVs in the development of NASH and the preclinical evidence related to stem cell-derived EVs as a potential therapeutic strategy for NASH. Moreover, possible strategies involving EVs as clinical diagnostic, staging and prognostic biomarkers for NASH are summarized.

Lipotoxicity and immunometabolism in ischemic acute kidney injury: current perspectives and future directions

Dysregulated lipid metabolism is implicated in the pathophysiology of a range of kidney diseases. The specific mechanisms through which lipotoxicity contributes to acute kidney injury (AKI) remain poorly understood. Herein we review the cardinal features of lipotoxic injury in ischemic kidney injury; lipid accumulation and mitochondrial lipotoxicity. We then explore a new mechanism of lipotoxicity, what we define as "immunometabolic" lipotoxicity, and discuss the potential therapeutic implications of targeting this lipotoxicity using lipid lowering medications.

Cholesterol Exacerbates the Pathophysiology of Non-Alcoholic Steatohepatitis by Upregulating Hypoxia-Inducible Factor 1 and Modulating Microcirculatory Dysfunction

Cholesterol is a pivotal lipotoxic molecule that contributes to the progression of Non-Alcoholic Steatohepatitis NASH). Additionally, microcirculatory changes are critical components of Non-Alcoholic Fatty Liver Disease (NAFLD) pathogenesis. This study aimed to investigate the role of cholesterol as an insult that modulates microcirculatory damage in NAFLD and the underlying mechanisms. The experimental model was established in male C57BL/6 mice fed a high-fat high-carbohydrate (HFHC) diet for 39 weeks. Between weeks 31-39, 2% cholesterol was added to the HFHC diet in a subgroup of mice. Leukocyte recruitment and hepatic stellate cells (HSC) activation in microcirculation were assessed using intravital microscopy. The hepatic microvascular blood flow (HMBF) was measured using laser speckle flowmetry. High cholesterol levels exacerbated hepatomegaly, hepatic steatosis, inflammation, fibrosis, and leukocyte recruitment compared to the HFHC group. In addition, cholesterol decreased the HMBF-cholesterol-induced activation of HSC and increased HIF1A expression in the liver. Furthermore, cholesterol promoted a pro-inflammatory cytokine profile with a Th1-type immune response (IFN-γ/IL-4). These findings suggest cholesterol exacerbates NAFLD progression through microcirculatory dysfunction and HIF1A upregulation through hypoxia and inflammation. This study highlights the importance of cholesterol-induced lipotoxicity, which causes microcirculatory dysfunction associated with NAFLD pathology, thus reinforcing the potential of lipotoxicity and microcirculation as therapeutic targets for NAFLD.

Hepatic stellate cells induce an inflammatory phenotype in Kupffer cells via the release of extracellular vesicles

Liver fibrosis is the response of the liver to chronic liver inflammation. The communication between the resident liver macrophages (Kupffer cells [KCs]) and hepatic stellate cells (HSCs) has been mainly viewed as one-directional: from KCs to HSCs with KCs promoting fibrogenesis. However, recent studies indicated that HSCs may function as a hub of intercellular communications. Therefore, the aim of the present study was to investigate the role of HSCs on the inflammatory phenotype of KCs. Primary rat HSCs and KCs were isolated from male Wistar rats. HSCs-derived conditioned medium (CM) was harvested from different time intervals (Day 0-2: CM-D2 and Day 5-7: CM-D7) during the activation of HSCs. Extracellular vesicles (EVs) were isolated from CM by ultracentrifugation and evaluated by nanoparticle tracking analysis and western blot analysis. M1 and M2 markers of inflammation were measured by quantitative PCR and macrophage function by assessing phagocytic capacity. CM-D2 significantly induced the inflammatory phenotype in KCs, but not CM-D7. Neither CM-D2 nor CM-D7 affected the phagocytosis of KCs. Importantly, the proinflammatory effect of HSCs-derived CM is mediated via EVs released from HSCs since EVs isolated from CM mimicked the effect of CM, whereas EV-depleted CM lost its ability to induce a proinflammatory phenotype in KCs. In addition, when the activation of HSCs was inhibited, HSCs produced less EVs. Furthermore, the proinflammatory effects of CM and EVs are related to activating Toll-like receptor 4 (TLR4) in KCs. In conclusion, HSCs at an early stage of activation induce a proinflammatory phenotype in KCs via the release of EVs. This effect is absent in CM derived from HSCs at a later stage of activation and is dependent on the activation of TLR4 signaling pathway.

The Lasting Effects of COVID-19 on the Progression of Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD)

It is estimated that around 30% of the population living in Western countries has metabolic dysfunction-associated steatotic liver disease (MASLD), a spectrum of pathology (not attributed to alcohol/substance intake) initiated by steatosis and progression toward inflammation and irreversible fibrosis metabolic dysfunction-associated steatohepatitis (MASH). With inflammation being a key component of the transition to MASH, it raises the question of whether the ongoing COVID-19 pandemic, which has notoriously induced hyperinflammatory states, may influence the progression of MASLD. Specifically, it remains unclear if the potential chronic sequelae of COVID-19 in patients who recovered from it may increase the predisposition for MASH. Since MASH maintains a high risk for hepatocellular carcinoma, liver failure, and the need for a liver transplant, the potential additive effects of COVID-19 could prove critical to study. Thus, the objective of this study was to conduct a literature review to examine if COVID-19 could have chronic sequelae that affect the progression of MASLD pathogenesis. It was hypothesized that severe cases of COVID-19 could induce systemic inflammation, metabolic changes, and lasting gut microbiome alterations that lead to inflammatory and fibrotic changes in the liver, similar to those seen in MASH. A scoping review of the literature was conducted utilizing the PubMed database. Studies that examined hepatobiliary pathology, gut microbiome, systemic inflammation, metabolic changes, drug-induced liver injury (DILI), and hypoxia seen in COVID-19 were included. Human studies of adult cohorts, animal models, and in vitro experiments were included. Genetic components of MASLD were not examined. Exclusion criteria also encompassed any studies not referencing the hepatobiliary, gastrointestinal tract, portal system, or systemic circulation. Findings indicated a frequent trend of elevated liver enzymes, mild steatosis, Kupffer cell hyperplasia, and hepatobiliary congestion. It was found that direct cytopathic effects on hepatocytes were unlikely, but the direct viral insult of cholangiocytes was a potential complication. High serum levels of IL-1, TNF-a, and MCP-1, in COVID-19 were found as potential risk factors for MASH development. Hypoxia, altered lipid metabolism, and iatrogenic DILI were also proposed as potential precipitators of MASH development. Notably, lasting changes in gut microbiome were also frequently observed and correlated closely with those seen in MASH.

Management of non-alcoholic fatty liver disease patients with sleep apnea syndrome

Nonalcoholic fatty liver disease (NAFLD) is strongly associated with sleep apnea syndrome (SAS). Many NAFLD patients have SAS, and obstructive sleep apnea hypopnea syndrome is also considered to be an independent risk factor for NAFLD, as it contributes to the progression of NAFLD via oxidative stress, lipid peroxidation, inflammation, and insulin resistance. This review aims to provide some recommendations for the management of NAFLD patients with SAS, including diet, exercise, weight loss, and continuous positive airway pressure. This review also highlights the importance of effective strategies in NAFLD prevention and treatment.

The Role of Extracellular Vesicles in Liver Pathogenesis

Extracellular vesicles (EVs) are generated by cells in the form of exosomes, microvesicles, and apoptotic bodies. They can be taken up by neighboring cells, and their contents can have functional impact on the cells that engulf them. As the mediators of intercellular communication, EVs can play important roles in both physiological and pathologic contexts. In addition, early detection of EVs in different body fluids may offer a sensitive diagnostic tool for certain diseases, such as cancer. Furthermore, targeting specific EVs may also become a promising therapeutic approach. This review summarizes the latest findings of EVs in the field of liver research, with a focus on the different contents of the EVs and their impact on liver function and on the development of inflammation, fibrosis, and tumor in the liver. The goal of this review is to provide a succinct account of the various molecules that can mediate the function of EVs so the readers may apply this knowledge to their own research.

Intermittent hypoxia aggravates non-alcoholic fatty liver disease via RIPK3-dependent necroptosis-modulated Nrf2/NFκB signaling pathway

AIMS

Hepatocyte necroptosis is a critical event in the progression of non-alcoholic fatty liver disease (NAFLD). Obstructive sleep apnea hypopnea syndrome (OSAHS) and chronic intermittent hypoxia (CIH) may be linked with the pathogenesis and the severity of NAFLD. However, the potential role of necroptosis in OSAHS-associated NAFLD has not been evaluated. The present study investigated whether IH could affect NAFLD progression through promoting receptor-interacting protein kinase-3 (RIPK3)-dependent necroptosis, oxidative stress, and inflammatory response, and further elucidated the underlying molecular mechanisms.

MAIN METHODS

LO2 cells were treated with palmitic acid (PA) and subjected to IH, and necroptosis, oxidative stress, and inflammation were assessed. The high-fat choline-deficient (HFCD)-fed mouse model was also used to assess the effects of CIH in experimental NAFLD in vivo.

KEY FINDINGS

In this study, we found that RIPK3-mediated necroptosis was activated both in the PA plus IH-treated LO2 cells and liver of HFCD/CIH mice, and which could trigger oxidative stress and inflammatory response by decreasing Nrf2 and increasing p-P65. RIPK3 downregulation significantly reduced hepatocyte necroptosis, and ameliorated oxidative stress and inflammation through modulating Nrf2/NFκB pathway in vitro and vivo. Similarly, pretreatment with TBHQ, an activator of Nrf2, effectively blocked the generation of oxidative productions and inflammatory cytokines. In addition, RIPK3 inhibitor GSK-872 or TBHQ administration obviously alleviated hepatic injury, including histology, transaminase activities, and triglyceride contents in vivo.

SIGNIFICANCE

IH aggravates NAFLD via RIPK3-dependent necroptosis-modulated Nrf2/NFκB signaling pathway, and which should be considered as a potential therapeutic strategy for the treatment of NAFLD with OSASH.

Insights into Nonalcoholic Fatty-Liver Disease Heterogeneity

The acronym nonalcoholic fatty-liver disease (NAFLD) groups a heterogeneous patient population. Although in many patients the primary driver is metabolic dysfunction, a complex and dynamic interaction of different factors (i.e., sex, presence of one or more genetic variants, coexistence of different comorbidities, diverse microbiota composition, and various degrees of alcohol consumption among others) takes place to determine disease subphenotypes with distinct natural history and prognosis and, eventually, different response to therapy. This review aims to address this topic through the analysis of existing data on the differential contribution of known factors to the pathogenesis and clinical expression of NAFLD, thus determining the different clinical subphenotypes observed in practice. To improve our understanding of NAFLD heterogeneity and the dominant drivers of disease in patient subgroups would predictably impact on the development of more precision-targeted therapies for NAFLD.

MicroRNA in extracellular vesicles regulates inflammation through macrophages under hypoxia

Extracellular vesicle (EV), critical mediators of cell-cell communication, allow cells to exchange proteins, lipids, and genetic material and therefore profoundly affect the general homeostasis. A hypoxic environment can affect the biogenesis and secrete of EVs, and the cargoes carried can participate in a variety of physiological and pathological processes. In hypoxia-induced inflammation, microRNA(miRNA) in EV participates in transcriptional regulation through various pathways to promote or reduce the inflammatory response. Meanwhile, as an important factor of immune response, the polarization of macrophages is closely linked to miRNAs, which will eventually affect the inflammatory state. In this review, we outline the possible molecular mechanism of EV changes under hypoxia, focusing on the signaling pathways of several microRNAs involved in inflammation regulation and describing the process and mechanism of EV-miRNAs regulating macrophage polarization in hypoxic diseases.

Dermal exposure to cobalt studied in vitro in keratinocytes - effects of cobalt exposure on inflammasome activated cytokines, and mRNA response

BACKGROUND

Cobalt is a dermal sensitizer, and keratinocytes respond to cobalt exposure by releasing proinflammatory mediators, regulating the immune response.

OBJECTIVE

To determine the effect of cobalt on the inflammasome associated cytokine- and gene expression in cultured human keratinocytes (HaCaT). Cultivation in low- or high calcium conditions model separate differentiation states of keratinocytes in the skin.

METHOD

HaCaT cells in two different states of differentiation were exposed to cobalt chloride and caspase-1 activity as well as the production of IL-1β, IL-18 and gene expression of IL1B, IL18, NLRP3, CASP1, and PYCARD was quantified.

RESULTS

High cobalt chloride exposure mediated significant increase in caspase-1 activity, cytokine levels, and IL1B and NLRP3 expression with a corresponding regulatory decrease for CASP1 and PYCARD expression. No difference between high- and low calcium culturing conditions modelling differentiation states was detected.

CONCLUSIONS

Our data suggest that HaCaT cells respond with inflammmasome associated activity upon cobalt exposure in a concentration-dependent manner. These mechanisms could be of importance for the understanding of the pathophysiology behind allergic sensitization to dermal cobalt exposure.

Protective effect of Salidroside on hypoxia-related liver oxidative stress and inflammation via Nrf2 and JAK2/STAT3 signaling pathways

High-altitude hypoxia-induced oxidative stress and inflammation played an essential role in the incidence and development of liver injury. Salidroside (Sal), a phenylpropanoid glycoside extracted from the plant Rhodiola rosea, has recently demonstrated antioxidant, anti-inflammatory, and antihypoxia properties. Herein, we hypothesized that salidroside may alleviate hypoxia-induced liver injury via antioxidant and antiinflammatory-related pathways. A high-altitude hypoxia animal model was established using hypobaric chamber. Male SD rats were randomly divided into the control group, hypoxia group, control +Sal group, and hypoxia +Sal group. Salidroside treatment significantly inhibited hypoxia-induced increases of serum and hepatic pro-inflammatory cytokines release, hepatic ROS production and MDA contents; attenuated hypoxia-induced decrease of hepatic SOD, CAT, and GSH-Px activities. Furthermore, salidroside treatment also potentiated the activation of Nrf2-mediated anti-oxidant pathway, as indicated by upregulation of n-Nrf2 and its downstream HO-1 and NQO-1. In vitro study found that blocking the Nrf2 pathway using specific inhibitor ML385 significantly reversed the protective effect of salidroside on hypoxia-induced liver oxidative stress. In addition, salidroside treatment significantly inhibited hepatic pro-inflammatory cytokines release via JAK2/STAT3-mediated pathway. Taken together, our findings suggested that salidroside protected against hypoxia-induced hepatic oxidative stress and inflammation via Nrf2 and JAK2/STAT3 signaling pathways.

Role of extracellular vesicles in liver diseases and their therapeutic potential

More than eight hundred million people worldwide have chronic liver disease, with two million deaths per year. Recurring liver injury results in fibrogenesis, progressing towards cirrhosis, for which there doesn't exists any cure except liver transplantation. Better understanding of the mechanisms leading to cirrhosis and its complications is needed to develop effective therapies. Extracellular vesicles (EVs) are released by cells and are important for cell-to-cell communication. EVs have been reported to be involved in homeostasis maintenance, as well as in liver diseases. In this review, we present current knowledge on the role of EVs in non-alcoholic fatty liver disease and non-alcoholic steatohepatitis, alcohol-associated liver disease, chronic viral hepatitis, primary liver cancers, acute liver injury and liver regeneration. Moreover, therapeutic strategies involving EVs as targets or as tools to treat liver diseases are summarized.

Problems of Pathogenesis and Pathogenetic Therapy of COVID-19 from the Perspective of the General Theory of Pathological Systems (General Pathological Processes)

The COVID-19 pandemic examines not only the state of actual health care but also the state of fundamental medicine in various countries. Pro-inflammatory processes extend far beyond the classical concepts of inflammation. They manifest themselves in a variety of ways, beginning with extreme physiology, then allostasis at low-grade inflammation, and finally the shockogenic phenomenon of "inflammatory systemic microcirculation". The pathogenetic core of critical situations, including COVID-19, is this phenomenon. Microcirculatory abnormalities, on the other hand, lie at the heart of a specific type of general pathological process known as systemic inflammation (SI). Systemic inflammatory response, cytokine release, cytokine storm, and thrombo-inflammatory syndrome are all terms that refer to different aspects of SI. As a result, the metabolic syndrome model does not adequately reflect the pathophysiology of persistent low-grade systemic inflammation (ChSLGI). Diseases associated with ChSLGI, on the other hand, are risk factors for a severe COVID-19 course. The review examines the role of hypoxia, metabolic dysfunction, scavenger receptors, and pattern-recognition receptors, as well as the processes of the hemophagocytic syndrome, in the systemic alteration and development of SI in COVID-19.

Remodeling of Mitochondrial Plasticity: The Key Switch from NAFLD/NASH to HCC

Hepatocellular carcinoma (HCC) is the most common primary malignancy of the liver and the third-leading cause of cancer-related mortality. Currently, the global burden of nonalcoholic fatty liver disease (NAFLD) has dramatically overcome both viral and alcohol hepatitis, thus becoming the main cause of HCC incidence. NAFLD pathogenesis is severely influenced by lifestyle and genetic predisposition. Mitochondria are highly dynamic organelles that may adapt in response to environment, genetics and epigenetics in the liver ("mitochondrial plasticity"). Mounting evidence highlights that mitochondrial dysfunction due to loss of mitochondrial flexibility may arise before overt NAFLD, and from the early stages of liver injury. Mitochondrial failure promotes not only hepatocellular damage, but also release signals (mito-DAMPs), which trigger inflammation and fibrosis, generating an adverse microenvironment in which several hepatocytes select anti-apoptotic programs and mutations that may allow survival and proliferation. Furthermore, one of the key events in malignant hepatocytes is represented by the remodeling of glucidic-lipidic metabolism combined with the reprogramming of mitochondrial functions, optimized to deal with energy demand. In sum, this review will discuss how mitochondrial defects may be translated into causative explanations of NAFLD-driven HCC, emphasizing future directions for research and for the development of potential preventive or curative strategies.

Nonalcoholic Fatty Liver Disease: Focus on New Biomarkers and Lifestyle Interventions

Nonalcoholic fatty liver disease (NAFLD) is considered a hepatic manifestation of metabolic syndrome, characterized from pathological changes in lipid and carbohydrate metabolism. Its main characteristics are excessive lipid accumulation and oxidative stress, which create a lipotoxic environment in hepatocytes leading to liver injury. Recently, many studies have focused on the identification of the genetic and epigenetic modifications that also contribute to NAFLD pathogenesis and their prognostic implications. The present review is aimed to discuss on cellular and metabolic alterations associated with NAFLD, which can be helpful to identify new noninvasive biomarkers. The identification of accumulated lipids in the cell membranes, as well as circulating cytokeratins and exosomes, provides new insights in understanding of NAFLD. This review also suggests that lifestyle modifications remain the main prevention and/or treatment for NAFLD.

A rapid juvenile murine model of nonalcoholic steatohepatitis (NASH): Chronic intermittent hypoxia exacerbates Western diet-induced NASH

AIMS

Many dietary NASH models require a long duration to establish (4-6 months). Chronic intermittent hypoxia (CIH), a cardinal hallmark of obstructive sleep apnea (OSA), may accelerate the progression of pediatric nonalcoholic fatty liver disease (NAFLD). However, diet-induced obese (DIO) mice exposed to CIH have not been perceived as a fast or reliable tool in NASH research. This study was designed to establish a rapid juvenile murine NASH model, and determine whether the combination of CIH and a western-style diet (hypercaloric fatty diet plus high fructose) can fully display key pathologic features of NASH.

METHODS

C57BL/6 N mice (3 weeks old) fed a control diet or western diet (WD) were exposed to CIH (9% nadir of inspired oxygen levels) or room air for 6 and 12 weeks.

KEY FINDINGS

The Control/CIH group mainly exhibited hyperinsulinemia and insulin resistance (IR). In contrast, mice fed a WD developed weight gain after 3 weeks, microvesicular steatosis in 6 weeks, and indices of metabolic disorders at 12 weeks. Furthermore, CIH exposure accelerated WD- induced macromicrovesicular steatosis (liver triglycerides and de novo lipogenesis), liver injury (ballooned hepatocytes and liver enzymes), lobular/portal inflammation (inflammatory cytokines and macrophage recruitment), and fibrogenesis (hydroxyproline content and TGF-β protein). Notably, only the WD/CIH group exhibited elevated hepatic MDA content, protein levels of NOX4, α-SMA and collagen I, as well as reduced Nrf2 and HO-1 protein expression.

SIGNIFICANCE

WD/CIH treatment rapidly mimics the histological characteristics of pediatric NASH with metabolic dysfunction and fibrosis, representing an appropriate experimental model for NASH research.

How does hepatic lipid accumulation lead to lipotoxicity in non-alcoholic fatty liver disease?

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD), characterized as excess lipid accumulation in the liver which is not due to alcohol use, has emerged as one of the major health problems around the world. The dysregulated lipid metabolism creates a lipotoxic environment which promotes the development of NAFLD, especially the progression from simple steatosis (NAFL) to non-alcoholic steatohepatitis (NASH).

PURPOSEAND AIM

This review focuses on the mechanisms of lipid accumulation in the liver, with an emphasis on the metabolic fate of free fatty acids (FFAs) in NAFLD and presents an update on the relevant cellular processes/mechanisms that are involved in lipotoxicity. The changes in the levels of various lipid species that result from the imbalance between lipolysis/lipid uptake/lipogenesis and lipid oxidation/secretion can cause organellar dysfunction, e.g. ER stress, mitochondrial dysfunction, lysosomal dysfunction, JNK activation, secretion of extracellular vesicles (EVs) and aggravate (or be exacerbated by) hypoxia which ultimately lead to cell death. The aim of this review is to provide an overview of how abnormal lipid metabolism leads to lipotoxicity and the cellular mechanisms of lipotoxicity in the context of NAFLD.

Role of Oxidative Stress in the Pathogenesis of Non-Alcoholic Fatty Liver Disease: Implications for Prevention and Therapy

Oxidative stress (OxS) is considered a major factor in the pathophysiology of inflammatory chronic liver diseases, including non-alcoholic liver disease (NAFLD). Chronic impairment of lipid metabolism is closely related to alterations of the oxidant/antioxidant balance, which affect metabolism-related organelles, leading to cellular lipotoxicity, lipid peroxidation, chronic endoplasmic reticulum (ER) stress, and mitochondrial dysfunction. Increased OxS also triggers hepatocytes stress pathways, leading to inflammation and fibrogenesis, contributing to the progression of non-alcoholic steatohepatitis (NASH). The antioxidant response, regulated by the Nrf2/ARE pathway, is a key component in this process and counteracts oxidative stress-induced damage, contributing to the restoration of normal lipid metabolism. Therefore, modulation of the antioxidant response emerges as an interesting target to prevent NAFLD development and progression. This review highlights the link between disturbed lipid metabolism and oxidative stress in the context of NAFLD. In addition, emerging potential therapies based on antioxidant effects and their likely molecular targets are discussed.

Extracellular Vesicles in the Development of the Non-Alcoholic Fatty Liver Disease: An Update

Non-alcoholic fatty liver disease (NAFLD) is a broad spectrum of liver damage disease from a simple fatty liver (steatosis) to more severe liver conditions such as non-alcoholic steatohepatitis (NASH), fibrosis, and cirrhosis. Extracellular vesicles (EVs) are a heterogeneous group of small membrane vesicles released by various cells in normal or diseased conditions. The EVs carry bioactive components in their cargos and can mediate the metabolic changes in recipient cells. In the context of NAFLD, EVs derived from adipocytes are implicated in the development of whole-body insulin resistance (IR), the hepatic IR, and fatty liver (steatosis). Excessive fatty acid accumulation is toxic to the hepatocytes, and this lipotoxicity can induce the release of EVs (hepatocyte-EVs), which can mediate the progression of fibrosis via the activation of nearby macrophages and hepatic stellate cells (HSCs). In this review, we summarized the recent findings of adipocyte- and hepatocyte-EVs on NAFLD disease development and progression. We also discussed previous studies on mesenchymal stem cell (MSC) EVs that have garnered attention due to their effects on preventing liver fibrosis and increasing liver regeneration and proliferation.

COVID-19 and non-alcoholic fatty liver disease: Two intersecting pandemics

BACKGROUND

Initial evidence from China suggests that most vulnerable subjects to COVID-19 infection suffer from pre-existing illness, including metabolic abnormalities. The pandemic characteristics and high-lethality rate of COVID-19 infection have raised concerns about interactions between virus pathobiology and components of the metabolic syndrome.

METHODS

We harmonized the information from the recent existing literature on COVID-19 acute pandemic and mechanisms of damage in non-alcoholic fatty liver disease (NAFLD), as an example of chronic (non-communicable) metabolic pandemic.

RESULTS

COVID-19-infected patients are more fragile with underlying metabolic illness, including hypertension, cardiovascular disease, type 2 diabetes, chronic lung diseases (e.g. asthma, chronic obstructive pulmonary disease and emphysema) and metabolic syndrome. During metabolic abnormalities, expansion of metabolically active fat ('overfat condition') parallels chronic inflammatory changes, development of insulin resistance and accumulation of fat in configuring NAFLD. The deleterious interplay of inflammatory pathways chronically active in NAFLD and acutely in COVID-19-infected patients, can explain liver damage in a subgroup of patients and might condition a worse outcome in metabolically compromised NAFLD patients. In a subgroup of patients with NAFLD, the underlying liver fibrosis might represent an additional and independent risk factor for severe COVID-19 illness, irrespective of metabolic comorbidities.

CONCLUSIONS

NAFLD can play a role in the outcome of COVID-19 illness due to frequent association with comorbidities. Initial evidences suggest that increased liver fibrosis in NAFLD might affect COVID-19 outcome. In addition, long-term monitoring of post-COVID-19 NAFLD patients is advisable, to document further deterioration of liver damage. Further studies are required in this field.

Non-alcoholic Fatty Liver Disease and Alcohol-Related Liver Disease: Two Intertwined Entities

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease worldwide, with a prevalence of 25-30%. Since its first description in 1980, NAFLD has been conceived as a different entity from alcohol-related fatty liver disease (ALD), despite that, both diseases have an overlap in the pathophysiology, share genetic-epigenetic factors, and frequently coexist. Both entities are characterized by a broad spectrum of histological features ranging from isolated steatosis to steatohepatitis and cirrhosis. Distinction between NAFLD and ALD is based on the amount of consumed alcohol, which has been arbitrarily established. In this context, a proposal of positive criteria for NAFLD diagnosis not considering exclusion of alcohol consumption as a prerequisite criterion for diagnosis had emerged, recognizing the possibility of a dual etiology of fatty liver in some individuals. The impact of moderate alcohol use on the severity of NAFLD is ill-defined. Some studies suggest protective effects in moderate doses, but current evidence shows that there is no safe threshold for alcohol consumption for NAFLD. In fact, given the synergistic effect between alcohol consumption, obesity, and metabolic dysfunction, it is likely that alcohol use serves as a significant risk factor for the progression of liver disease in NAFLD and metabolic syndrome. This also affects the incidence of hepatocellular carcinoma. In this review, we summarize the overlapping pathophysiology of NAFLD and ALD, the current data on alcohol consumption in patients with NAFLD, and the effects of metabolic dysfunction and overweight in ALD.

Tetramethylpyrazine alleviates acute kidney injury by inhibiting NLRP3/HIF‑1α and apoptosis

The aim of the present study was to investigate the protective effect and underlying mechanism of tetramethylpyrazine (TMP) on renal ischemia reperfusion injury (RIRI) in rats, which refers to the injury caused by the restoration of blood supply and reperfusion of the kidney after a period of ischemia. Sprague‑Dawley rats were randomly divided into a Sham group, renal ischemia‑reperfusion (I/R) group and TMP group. TMP hydrochloride (40 mg/kg, 6 h intervals) was given via intraperitoneal injection immediately after reperfusion in the TMP group, after 24 h the kidney tissues were taken for follow‑up experiments. Pathological changes in the kidney tissues were observed by periodic acid‑Schiff staining. Renal function was assessed by measuring levels of serum creatinine and blood urea nitrogen, and inflammatory cytokines tumor necrosis factor (TNF)‑α and interleukin (IL)‑6. Renal cell apoptosis was detected by TUNEL‑DAPI double staining, mRNA and protein changes were analyzed by reverse transcription‑quantitative PCR and western blotting. Cell viability was measured using a CCK‑8 assay. It was found that the renal tissues of the sham operation group were notably abnormal, and the renal tissues of the I/R group were damaged, while the renal tissues of the TMP group were less damaged compared with those of the I/R group. Compared with the I/R group, the serum creatinine and blood urea nitrogen levels in the TMP group were low (all P<0.05), levels of inflammatory cytokines TNF‑α and IL‑6 decreased, the apoptotic rate was low (all P<0.05), and the relative expression levels of nucleotide‑oligomerization domain‑like receptor 3 (NLRP3) protein and mRNA in renal tissues were low (all P<0.05). The expression levels of hypoxia‑inducible factor 1‑α and NLRP3 increased after oxygen and glucose deprivation (OGD), and reduced after treatment with OGD and TMP (all P<0.05). It was concluded that TMP can reduce renal injury and improve renal function in RIRI rats, and its mechanism may be related to the reduction of NLRP3 expression in renal tissues.

Extracellular Vesicles in NAFLD/ALD: From Pathobiology to Therapy

In recent years, knowledge on the biology and pathobiology of extracellular vesicles (EVs) has exploded. EVs are submicron membrane-bound structures secreted from different cell types containing a wide variety of bioactive molecules (e.g., proteins, lipids, and nucleic acids (coding and non-coding RNA) and mitochondrial DNA). EVs have important functions in cell-to-cell communication and are found in a wide variety of tissues and body fluids. Better delineation of EV structures and advances in the isolation and characterization of their cargo have allowed the diagnostic and therapeutic implications of these particles to be explored. In the field of liver diseases, EVs are emerging as key players in the pathogenesis of both nonalcoholic liver disease (NAFLD) and alcoholic liver disease (ALD), the most prevalent liver diseases worldwide, and their complications, including development of hepatocellular carcinoma. In these diseases, stressed/damaged hepatocytes release large quantities of EVs that contribute to the occurrence of inflammation, fibrogenesis, and angiogenesis, which are key pathobiological processes in liver disease progression. Moreover, the specific molecular signatures of released EVs in biofluids have allowed EVs to be considered as promising candidates to serve as disease biomarkers. Additionally, different experimental studies have shown that EVs may have potential for therapeutic use as a liver-specific delivery method of different agents, taking advantage of their hepatocellular uptake through interactions with specific receptors. In this review, we focused on the most recent findings concerning the role of EVs as new structures mediating autocrine and paracrine intercellular communication in both ALD and NAFLD, as well as their potential use as biomarkers of disease severity and progression. Emerging therapeutic applications of EVs in these liver diseases were also examined, along with the potential for successful transition from bench to clinic.