Myeloid-specific IRE1alpha deletion reduces tumour development in a diabetic, non-alcoholic steatohepatitis-induced hepatocellular carcinoma mouse model

Remodeling the hepatic immune microenvironment and demolishing T cell traps to enhance immunotherapy efficacy in liver metastasis

Immune checkpoint inhibitors (ICIs) exhibit compromised therapeutic efficacy in many patients with advanced cancers, particularly those with liver metastases. Much of this incapability can be ascribed as an irresponsiveness resulting from the "cold" hepatic tumor microenvironment that acts as T cell "traps" for which there currently lack countermeasures. We report a novel nanomedicine that converts the hepatic immune microenvironment to a "hot" phenotype by targeting hepatic macrophage-centric T cell elimination. Using the nanomedicine, composed of KIRA6 (an endothelium reticulum stress inhibitor), α-Tocopherol nanoemulsions, and anti-PD1 antibodies, we found its potency in murine models of orthotopic colorectal tumors and hepatic metastases, restoring immune responses and enhancing anti-tumor effects. A post-treatment scrutiny of the immune microenvironment landscape in the liver reveals repolarization of immunosuppressive hepatic macrophages, upregulation of Th1-like effector CD4+ T cells, and rejuvenation of dendritic cells along with CD8+ T cells. These findings suggest adaptations of liver-centric immune milieu modulation strategies to improve the efficacy of ICIs for a variety of "cold" tumors and their liver metastases.

Autophagy and the unfolded protein response shape the non-alcoholic fatty liver landscape: decoding the labyrinth

The incidence of nonalcoholic fatty liver disease (NAFLD) is on the rise, mirroring a global surge in diabetes and metabolic syndrome, as its major leading causes. NAFLD represents a spectrum of liver disorders, ranging from nonalcoholic fatty liver (NAFL) to nonalcoholic steatohepatitis (NASH), which can potentially progress to cirrhosis and hepatocellular carcinoma (HCC). Mechanistically, we know the unfolded protein response (UPR) as a protective cellular mechanism, being triggered under circumstances of endoplasmic reticulum (ER) stress. The hepatic UPR is turned on in a broad spectrum of liver diseases, including NAFLD. Recent data also defines molecular mechanisms that may underlie the existing correlation between UPR activation and NAFLD. More interestingly, subsequent studies have demonstrated an additional mechanism, i.e. autophagy, to be involved in hepatic steatosis, and thus NAFLD pathogenesis, principally by regulating the insulin sensitivity, hepatocellular injury, innate immunity, fibrosis, and carcinogenesis. All these findings suggest possible mechanistic roles for autophagy in the progression of NAFLD and its complications. Both UPR and autophagy are dynamic and interconnected fluxes that act as protective responses to minimize the harmful effects of hepatic lipid accumulation, as well as the ER stress during NAFLD. The functions of UPR and autophagy in the liver, together with findings of decreased hepatic autophagy in correlation with conditions that predispose to NAFLD, such as obesity and aging, suggest that autophagy and UPR, alone or combined, may be novel therapeutic targets against the disease. In this review, we discuss the current evidence on the interplay between autophagy and the UPR in connection to the NAFLD pathogenesis.

Drug targets regulate systemic metabolism and provide new horizons to treat nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH), is the advanced stage of nonalcoholic fatty liver disease (NAFLD) with rapidly rising global prevalence. It is featured with severe hepatocyte apoptosis, inflammation and hepatic lipogenesis. The drugs directly targeting the processes of steatosis, inflammation and fibrosis are currently under clinical investigation. Nevertheless, the long-term ineffectiveness and remarkable adverse effects are well documented, and new concepts are required to tackle with the root causes of NASH progression. We critically assess the recently validated drug targets that regulate the systemic metabolism to ameliorate NASH. Thermogenesis promoted by mitochondrial uncouplers restores systemic energy expenditure. Furthermore, regulation of mitochondrial proteases and proteins that are pivotal for intracellular metabolic homeostasis normalize mitochondrial function. Secreted proteins also improve systemic metabolism, and NASH is ameliorated by agonizing receptors of secreted proteins with small molecules. We analyze the drug design, the advantages and shortcomings of these novel drug candidates. Meanwhile, the structural modification of current NASH therapeutics significantly increased their selectivity, efficacy and safety. Furthermore, the arising CRISPR-Cas9 screen strategy on liver organoids has enabled the identification of new genes that mediate lipid metabolism, which may serve as promising drug targets. In summary, this article discusses the in-depth novel mechanisms and the multidisciplinary approaches, and they provide new horizons to treat NASH.

Osteopontin characterizes bile duct-associated macrophages and correlates with liver fibrosis severity in primary sclerosing cholangitis

BACKGROUND AND AIMS

Primary sclerosing cholangitis (PSC) is an immune-mediated cholestatic liver disease for which pharmacological treatment options are currently unavailable. PSC is strongly associated with colitis and a disruption of the gut-liver axis, and macrophages are involved in the pathogenesis of PSC. However, how gut-liver interactions and specific macrophage populations contribute to PSC is incompletely understood.

APPROACH AND RESULTS

We investigated the impact of cholestasis and colitis on the hepatic and colonic microenvironment, and performed an in-depth characterization of hepatic macrophage dynamics and function in models of concomitant cholangitis and colitis. Cholestasis-induced fibrosis was characterized by depletion of resident KCs, and enrichment of monocytes and monocyte-derived macrophages (MoMFs) in the liver. These MoMFs highly express triggering-receptor-expressed-on-myeloid-cells-2 ( Trem2 ) and osteopontin ( Spp1 ), markers assigned to hepatic bile duct-associated macrophages, and were enriched around the portal triad, which was confirmed in human PSC. Colitis induced monocyte/macrophage infiltration in the gut and liver, and enhanced cholestasis-induced MoMF- Trem2 and Spp1 upregulation, yet did not exacerbate liver fibrosis. Bone marrow chimeras showed that knockout of Spp1 in infiltrated MoMFs exacerbates inflammation in vivo and in vitro , while monoclonal antibody-mediated neutralization of SPP1 conferred protection in experimental PSC. In human PSC patients, serum osteopontin levels are elevated compared to control, and significantly increased in advanced stage PSC and might serve as a prognostic biomarker for liver transplant-free survival.

CONCLUSIONS

Our data shed light on gut-liver axis perturbations and macrophage dynamics and function in PSC and highlight SPP1/OPN as a prognostic marker and future therapeutic target in PSC.

Immunologic Crosstalk of Endoplasmic Reticulum Stress Signaling in Bladder Cancer

Bladder cancer (BC) is a common malignant tumor of the urinary system. While current approaches involving adjuvant chemotherapy, radiotherapy, and immunotherapy have shown significant progress in BC treatment, challenges, such as recurrence and drug resistance, persist, especially in the case of muscle-invasive bladder cancer (MIBC). It is mainly due to the lack of pre-existing immune response cells in the tumor immune microenvironment. Micro-environmental changes (such as hypoxia and under-nutrition) can cause the aggregation of unfolded and misfolded proteins in the lumen, which induces endoplasmic reticulum (ER) stress. ER stress and its downstream signaling pathways are closely related to immunogenicity and tumor drug resistance. ER stress plays a pivotal role in a spectrum of processes within immune cells and the progression of BC cells, encompassing cell proliferation, autophagy, apoptosis, and resistance to therapies. Recent studies have increasingly recognized the potential of natural compounds to exhibit anti-BC properties through ER stress induction. Still, the efficacy of these natural compounds remains less than that of immune checkpoint inhibitors (ICIs). Currently, the ER stress-mediated immunogenic cell death (ICD) pathway is more encouraging, which can enhance ICI responses by mediating immune stemness. This article provides an overview of the recent developments in understanding how ER stress influences tumor immunity and its implications for BC. Targeting this pathway may soon emerge as a compelling therapeutic strategy for BC.

OCTN2 enhances PGC-1α-mediated fatty acid oxidation and OXPHOS to support stemness in hepatocellular carcinoma

BACKGROUND

The Metabolic reprogramming of tumor cells plays a vital role in the progression of hepatocellular carcinoma. Organic cation/carnitine transporter 2 (OCTN2), a sodium-ion dependent carnitine transporter and a sodium-ion independent tetraethylammonium (TEA) transporter, has been reported to contribute tumor malignancies and metabolic dysregulation in renal and esophageal carcinoma. However, the role of lipid metabolism deregulation mediated by OCTN2 in HCC cells has not been clarified.

METHODS

Bioinformatics analyses and immunohistochemistry assay were employed to identify OCTN2 expression in HCC tissues. The correlation between OCTN2 expression and prognosis was elucidated through K-M survival analysis. The expression and function of OCTN2 were examined via the assays of western blotting, sphere formation, cell proliferation, migration and invasion. The mechanism of OCTN2-mediated HCC malignancies was investigated through RNA-seq and metabolomic analyses. Furthermore, xenograft tumor models based on HCC cells with different OCTN2 expression levels were conducted to analyze the tumorigenic and targetable role of OCTN2 in vivo.

RESULTS

We found that gradually focused OCTN2 was significantly upregulated in HCC and tightly associated with poor prognosis. Additionally, OCTN2 upregulation promoted HCC cells proliferation and migration in vitro and augmented the growth and metastasis of HCC. Moreover, OCTN2 promoted the cancer stem-like properties of HCC by increasing fatty acid oxidation and oxidative phosphorylation. Mechanistically, PGC-1α signaling participated in the HCC cancer stem-like properties mediated by OCTN2 overexpression, which is confirmed by in vitro and in vivo analyses. Furthermore, OCTN2 upregulation may be transcriptionally activated by YY1 in HCC. Particularly, treatment with mildronate, an inhibitor of OCTN2, showed a therapeutic influence on HCC in vitro and in vivo.

CONCLUSIONS

Our findings demonstrate that OCTN2 plays a critical metabolic role in HCC cancer stemness maintenance and HCC progression, providing evidence for OCTN2 as a promising target for HCC therapy.

Control of immune cell function by the unfolded protein response

Initiating and maintaining optimal immune responses requires high levels of protein synthesis, folding, modification and trafficking in leukocytes, which are processes orchestrated by the endoplasmic reticulum. Importantly, diverse extracellular and intracellular conditions can compromise the protein-handling capacity of this organelle, inducing a state of 'endoplasmic reticulum stress' that activates the unfolded protein response (UPR). Emerging evidence shows that physiological or pathological activation of the UPR can have effects on immune cell survival, metabolism, function and fate. In this Review, we discuss the canonical role of the adaptive UPR in immune cells and how dysregulation of this pathway in leukocytes contributes to diverse pathologies such as cancer, autoimmunity and metabolic disorders. Furthermore, we provide an overview as to how pharmacological approaches that modulate the UPR could be harnessed to control or activate immune cell function in disease.

Transient Kupffer cell depletion and subsequent replacement by infiltrating monocyte-derived cells does not alter the induction or progression of hepatocellular carcinoma

Due to a combination of rapid disease progression and the lack of curative treatment options, hepatocellular carcinoma (HCC) is one of the deadliest cancers worldwide. Infiltrated, monocyte-derived, tumor-associated macrophages are known to play a role in HCC pathogenesis, but the involvement of Kupffer cells (KCs) remains elusive. Here, we used the Clec4F-diphteria toxin receptor transgenic mouse model to specifically investigate the effect of KC depletion on HCC initiation, progression and neoplastic growth following liver resection. For this purpose, several HCC mouse models with varying underlying etiologies were used and partial hepatectomy was performed. Our results show that in HCC, developed on a fibrotic or non-alcoholic steatohepatitis background, depletion of embryonic KCs at the onset of HCC induction and the subsequent replacement by monocyte-derived KCs does not affect the tumor burden, tumor microenvironment or the phenotype of isolated KCs at end-stage disease. In non-chronic liver disease-associated diethylnitrosamine-induced HCC, ablation of Clec4F+ KCs did not alter tumor progression or neoplastic growth following liver resection. Our results show that temporal ablation of resident KCs does not impact HCC pathogenesis, neither in the induction phase nor in advanced disease, and indicate that bone marrow-derived KCs are able to swiftly repopulate the available KC niche and adopt their phenotype.

The contradictory roles of macrophages in non-alcoholic fatty liver disease and primary liver cancer-Challenges and opportunities

Chronic liver diseases from varying etiologies generally lead to liver fibrosis and cirrhosis. Among them, non-alcoholic fatty liver disease (NAFLD) affects roughly one-quarter of the world population, thus representing a major and increasing public health burden. Chronic hepatocyte injury, inflammation (non-alcoholic steatohepatitis, NASH) and liver fibrosis are recognized soils for primary liver cancer, particularly hepatocellular carcinoma (HCC), being the third most common cause for cancer-related deaths worldwide. Despite recent advances in liver disease understanding, therapeutic options on pre-malignant and malignant stages remain limited. Thus, there is an urgent need to identify targetable liver disease-driving mechanisms for the development of novel therapeutics. Monocytes and macrophages comprise a central, yet versatile component of the inflammatory response, fueling chronic liver disease initiation and progression. Recent proteomic and transcriptomic studies performed at singular cell levels revealed a previously overlooked diversity of macrophage subpopulations and functions. Indeed, liver macrophages that encompass liver resident macrophages (also named Kupffer cells) and monocyte-derived macrophages, can acquire a variety of phenotypes depending on microenvironmental cues, and thus exert manifold and sometimes contradictory functions. Those functions range from modulating and exacerbating tissue inflammation to promoting and exaggerating tissue repair mechanisms (i.e., parenchymal regeneration, cancer cell proliferation, angiogenesis, fibrosis). Due to these central functions, liver macrophages represent an attractive target for the treatment of liver diseases. In this review, we discuss the multifaceted and contrary roles of macrophages in chronic liver diseases, with a particular focus on NAFLD/NASH and HCC. Moreover, we discuss potential therapeutic approaches targeting liver macrophages.

Targeting endoplasmic reticulum stress-the responder to lipotoxicity and modulator of non-alcoholic fatty liver diseases

INTRODUCTION

Endoplasmic reticulum (ER) stress occurs with aberrant lipid accumulation and resultant adverse effects and widely exists in nonalcoholic fatty liver disease (NAFLD). It triggers the unfolded protein response (UPR) to restore ER homeostasis and actively participates in NAFLD pathological processes, including hepatic steatosis, inflammation, hepatocyte death, and fibrosis. Such acknowledges drive the discovery of novel NAFLD biomarker and therapeutic targets and the development of ER-stress targeted NAFLD drugs.

AREAS COVERED

This article discusses and updates the role of ER stress and UPR in NAFLD, the underlying action mechanism, and especially their full participation in NAFLD pathophysiology. It characterizes key molecular targets useful for the prevention and treatment of NAFLD and highlights the recent ER stress-targeted therapeutic strategies for NAFLD.

EXPERT OPINION

Targeting ER Stress is a valuable and promising strategy for NAFLD treatment, but its smooth translation into clinical application still requires better clarification of the different UPR patterns in diverse NAFLD physiological states. Further understanding of the distinct effects of these various patterns on NAFLD, the thresholds deciding their final impacts, and their actions via non-liver tissues and cells would be of great help to develop a precise and effective therapy for NAFLD. [Figure: see text].

The Gut-Liver Axis in Chronic Liver Disease: A Macrophage Perspective

Chronic liver disease (CLD) is a growing health concern which accounts for two million deaths per year. Obesity, alcohol overconsumption, and progressive cholestasis are commonly characterized by persistent low-grade inflammation and advancing fibrosis, which form the basis for development of end-stage liver disease complications, including hepatocellular carcinoma. CLD pathophysiology extends to the intestinal tract and is characterized by intestinal dysbiosis, bile acid dysregulation, and gut barrier disruption. In addition, macrophages are key players in CLD progression and intestinal barrier breakdown. Emerging studies are unveiling macrophage heterogeneity and driving factors of their plasticity in health and disease. To date, in-depth investigation of how gut-liver axis disruption impacts the hepatic and intestinal macrophage pool in CLD pathogenesis is scarce. In this review, we give an overview of the role of intestinal and hepatic macrophages in homeostasis and gut-liver axis disruption in progressive stages of CLD.

Dual Inhibition of Endoplasmic Reticulum Stress and Oxidation Stress Manipulates the Polarization of Macrophages under Hypoxia to Sensitize Immunotherapy

M2-tumor associated macrophages (TAMs) play an important role in tumor genesis, progression, and metastasis, and repolarizing M2-TAMs to immune-promoting M1 type is increasingly recognized as a promising strategy against the clinically intractable carcinomas. It is observed that M2 macrophages have a high tropism to the tumor hypoxic area, with their endoplasmic reticulum (ER) stress-associated IRE1-XBP1 pathway activated to inhibit cell glycolysis, promote oxidative phosphorylation (OXPHOS), and facilitate intracellular lipid accumulation, which in turn shapes the typical phenotypes of M2-TAMs, suggesting that manipulating the ER stress response of M2-TAMs might stand as a breakthrough for antitumor therapy. However, current attempts to repolarize M2 cells remain limited and are greatly challenged by the hypoxic nature of tumors. Also, the high level of reactive oxygen species (ROS) in the tumor microenvironment (TME) is favorable for the polarization of M2-TAMs. Here, we encapsulated KIRA6, an inhibitor of the IRE1-XBP1 pathway, into a reductive nanoemulsion containing α-tocopherol. Our α-T-K had dual inhibitory effects on the ER stress and oxidative stress. Both in vitro and in vivo experiments suggested that α-T-K effectively reprogrammed M2 macrophages even under hypoxia, achieved by increasing glycolysis and suppressing fatty acid oxidation (FAO). In addition, our data revealed that α-T-K not only delayed tumor growth but elevated the curative effect of PD-1 antibody. Our research demonstrated that simultaneous inhibition of ER stress and oxidative stress could effectively repolarize M2-TAMs under hypoxia, which not only filled the current gap in regulating the biological repolarization of macrophages under hypoxia but provided a meaningful reference for the clinical immunotherapy of sensitized anti-PD-1.

Lymphotoxin-β-receptor (LTβR) signaling on hepatocytes is required for liver regeneration after partial hepatectomy

Lymphotoxin-β-receptor deficient (LTβR-/-) and Tumor Necrosis Factor Receptor p55 deficient (TNFRp55-/-) mice show defects in liver regeneration (LR) after partial hepatectomy (PHx) with significantly increased mortality. LTβR and TNFRp55 belong to the core members of the TNF/TNFR superfamily. Interestingly, combined failure of LTβR and TNFRp55 signaling after PHx leads to a complete defect in LR. Here, we first addressed the question which liver cell population crucially requires LTβR signaling for efficient LR. To this end, mice with a conditionally targeted LTβR allele (LTβRfl/fl) were crossed to AlbuminCre and LysozymeMCre mouse lines to unravel the function of the LTβR on hepatocytes and monocytes/macrophages/Kupffer cells, respectively. Analysis of these mouse lines clearly reveals that LTβR is required on hepatocytes for efficient LR while no deficit in LR was found in LTβRfl/fl × LysMCre mice. Second, the molecular basis for the cooperating role of LTβR and TNFRp55 signaling pathways in LR was investigated by transcriptome analysis of etanercept treated LTβR-/- (LTβR-/-/ET) mice. Bioinformatic analysis and subsequent verification by qRT-PCR identified novel target genes (Cyclin-L2, Fas-Binding factor 1, interferon-related developmental regulator 1, Leucyl-tRNA Synthetase 2, and galectin-4) that are upregulated by LTβR/TNFRp55 signaling after PHx and fail to be upregulated after PHx in LTβR-/-/ET mice.

Endoplasmic Reticulum Stress and Autophagy in the Pathogenesis of Non-alcoholic Fatty Liver Disease (NAFLD): Current Evidence and Perspectives

PURPOSE OF REVIEW

Non-alcoholic fatty liver disease (NAFLD) is one of the most common causes of chronic liver disease with rising prevalence worldwide. Herein, we provide a comprehensive overview of the current knowledge supporting the role of ER stress and autophagy processes in NAFLD pathogenesis and progression. We also highlight the interrelation between these two pathways and the impact of ER stress and autophagy modulators on NAFLD treatment.

RECENT FINDINGS

The pathophysiological mechanisms involved in NAFLD progression are currently under investigation. The endoplasmic reticulum (ER) stress and the concomitant unfolded protein response (UPR) seem to contribute to its pathogenesis mainly due to high ER content in the liver which exerts significant metabolic functions and can be dysregulated. Furthermore, disruption of autophagy processes has also been identified in NAFLD. The crucial role of these two pathways in NAFLD is underlined by the fact that they have recently emerged as promising targets of therapeutic interventions. There is a greater need for finding the natural/chemical compounds and drugs which can modulate the ER stress pathway and autophagy for the treatment of NAFLD. Clarifying the inter-relation between these two pathways and their interaction with inflammatory and apoptotic mechanisms will allow the development of additional therapeutic options which can better target and reprogram the underlying pathophysiological pathways, aiming to attenuate NAFLD progression.

Anthracyclins Increase PUFAs: Potential Implications in ER Stress and Cell Death

Metabolic and personalized interventions in cancer treatment require a better understanding of the relationship between the induction of cell death and metabolism. Consequently, we treated three primary liver cancer cell lines with two anthracyclins (doxorubicin and idarubin) and studied the changes in the lipidome. We found that both anthracyclins in the three cell lines increased the levels of polyunsaturated fatty acids (PUFAs) and alkylacylglycerophosphoethanolamines (etherPEs) with PUFAs. As PUFAs and alkylacylglycerophospholipids with PUFAs are fundamental in lipid peroxidation during ferroptotic cell death, our results suggest supplementation with PUFAs and/or etherPEs with PUFAs as a potential general adjuvant of anthracyclins. In contrast, neither the markers of de novo lipogenesis nor cholesterol lipids presented the same trend in all cell lines and treatments. In agreement with previous research, this suggests that modulation of the metabolism of cholesterol could be considered a specific adjuvant of anthracyclins depending on the type of tumor and the individual. Finally, in agreement with previous research, we found a relationship across the different cell types between: (i) the change in endoplasmic reticulum (ER) stress, and (ii) the imbalance between PUFAs and cholesterol and saturated lipids. In the light of previous research, this imbalance partially explains the sensitivity to anthracyclins of the different cells. In conclusion, our results suggest that the modulation of different lipid metabolic pathways may be considered for generalized and personalized metabochemotherapies.

Hepatic macrophage accumulation with aging: cause for concern?

Aging is associated with chronic, low-grade inflammation that adversely affects physiological function. The liver regulates systemic inflammation; it is a source of cytokine production and also scavenges bacteria from the portal circulation to prevent infection of other organs. The cells with primary roles in these functions, hepatic macrophages, become more numerous in the liver with "normal" aging (i.e., in the absence of disease). Here, we demonstrate evidence and potential mechanisms for this phenomenon, which include augmented tumor necrosis factor-α (TNF-α) and intercellular adhesion molecule-1 (ICAM-1) expression in the liver. Also, we discuss how an age-related impairment in autophagy within macrophages leads to a pro-oxidative state and ensuing production of proinflammatory cytokines, particularly interleukin 6 (IL-6). Given that the liver is a rich source of macrophages, we posit that it represents a major source of the elevated systemic IL-6 observed with aging, which is associated with physiological dysfunction. Testing a causal role for liver macrophage production of IL-6 during aging remains a challenge, yet interventions that have targeted macrophages and/or IL-6 have demonstrated promise in treating age-related diseases. These studies have demonstrated an age-related, deleterious reprogramming of macrophage function, which worsens pathology. Therefore, hepatic macrophage accrual is indeed a cause for concern, and therapies that attenuate the aged phenotype of macrophages will likely prove useful in promoting healthy aging.

Characterization of the inflammatory microenvironment and hepatic macrophage subsets in experimental hepatocellular carcinoma models

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related death worldwide. HCC typically develops on a background of chronic inflammation and fibrosis with tumor associated macrophages (TAMs) playing an important role in chronic inflammation-induced HCC and progression. However, the liver harbors unique macrophages, resident liver Kupffer cells (KCs) and monocyte-derived macrophages (Mo-Mφ), and their contribution to HCC and to the population of TAMs is incompletely known. Here, we characterized the tumor microenvironment and the proportion and transcriptional profile of hepatic macrophages (Mφ) in two commonly used HCC mouse models. A gradually increased expression of inflammatory, immune regulatory, fibrotic and cell proliferation pathways and markers was observed during diethylnitrosamine (DEN)- and non-alcoholic steatohepatitis (NASH)-induced HCC development. The transcriptional phenotypes of isolated hepatic Mφ subsets were clearly distinct and shifted during HCC development, with mixed pro-inflammatory and tumor-promoting expression profiles. There were marked differences between the models as well, with Mφ in NASH-HCC exhibiting a more immunomodulatory phenotype, in conjunction with an upregulation of lipid metabolism genes. Our data show that at least some infiltrated macrophages display expression of pro-tumoral markers, and that Kupffer cells are part of the population of TAMs and enhance tumor progression. These insights are useful to further unravel sequential pathogenic events during hepatocarcinogenesis and direct future development of new treatment strategies for HCC.

Inhibiting P2Y12 in Macrophages Induces Endoplasmic Reticulum Stress and Promotes an Anti-Tumoral Phenotype

The P2Y12 receptor is an adenosine diphosphate responsive G protein-coupled receptor expressed on the surface of platelets and is the pharmacologic target of several anti-thrombotic agents. In this study, we use liver samples from mice with cirrhosis and hepatocellular carcinoma to show that P2Y12 is expressed by macrophages in the liver. Using in vitro methods, we show that inhibition of P2Y12 with ticagrelor enhances tumor cell phagocytosis by macrophages and induces an anti-tumoral phenotype. Treatment with ticagrelor also increases the expression of several actors of the endoplasmic reticulum (ER) stress pathways, suggesting activation of the unfolded protein response (UPR). Inhibiting the UPR with tauroursodeoxycholic acid (Tudca) diminishes the pro-phagocytotic effect of ticagrelor, thereby indicating that P2Y12 mediates macrophage function through activation of ER stress pathways. This could be relevant in the pathogenesis of chronic liver disease and cancer, as macrophages are considered key players in these inflammation-driven pathologies.

Thrombospondin-1: A Key Protein That Induces Fibrosis in Diabetic Complications

Fibrosis accompanies most common pathophysiological features of diabetes complications in different organs. It is characterized by an excessive accumulation of extracellular matrix (ECM) components, the response to which contributes to inevitable organ injury. The extracellular protein thrombospondin-1 (TSP-1), a kind of extracellular glycoprotein, is upregulated by the increased activity of some transcription factors and results in fibrosis by activating multiple pathways in diabetes. The results of studies from our team and other colleagues indicate that TSP-1 is associated with the pathological process leading to diabetic complications and is considered to be the most important factor in fibrosis. This review summarizes the molecular mechanism of increased TSP-1 induced by hyperglycemia and the role of TSP-1 in fibrosis during the development of diabetes complications.