Mechanobiology of portal hypertension.

The interplay between mechanical stimuli and cellular mechanobiology orchestrates the physiology of tissues and organs in a dynamic balance characterized by constant remodelling and adaptative processes. Environmental mechanical properties can be interpreted as a complex set of information and instructions that cells read continuously, and to which they respond. In cirrhosis, chronic inflammation and injury drive liver cells dysfunction, leading to excessive extracellular matrix deposition, sinusoidal pseudocapillarization, vascular occlusion and parenchymal extinction. These pathological events result in marked remodelling of the liver microarchitecture, which is cause and result of abnormal environmental mechanical forces, triggering and sustaining the long-standing and progressive process of liver fibrosis. Multiple mechanical forces such as strain, shear stress, and hydrostatic pressure can converge at different stages of the disease until reaching a point of no return where the fibrosis is considered non-reversible. Thereafter, reciprocal communication between cells and their niches becomes the driving force for disease progression. Accumulating evidence supports the idea that, rather than being a passive consequence of fibrosis and portal hypertension (PH), mechanical force-mediated pathways could themselves represent strategic targets for novel therapeutic approaches. In this manuscript, we aim to provide a comprehensive review of the mechanobiology of PH, by furnishing an introduction on the most important mechanisms, integrating these concepts into a discussion on the pathogenesis of PH, and exploring potential therapeutic strategies

Review: Vascular effects of PPARs in the context of NASH.

BACKGROUND Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors known to regulate glucose and fatty acid metabolism, inflammation, endothelial function and fibrosis. PPAR isoforms have been extensively studied in metabolic diseases, including type 2 diabetes and cardiovascular diseases. Recent data extend the key role of PPARs to liver diseases coursing with vascular dysfunction, including nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH). AIM This review summarises and discusses the pathobiological role of PPARs in cardiovascular diseases with a special focus on their impact and therapeutic potential in NAFLD and NASH. RESULTS AND CONCLUSIONS PPARs may be attractive for the treatment of NASH due to their liver-specific effects but also because of their efficacy in improving cardiovascular outcomes, which may later impact liver disease. Assessment of cardiovascular disease in the context of NASH trials is, therefore, of the utmost importance, both from a safety and efficacy perspective

IRF3 regulates neuroinflammatory responses and the expression of genes associated with Alzheimer's disease.

The pathological role of interferon signaling is emerging in neuroinflammatory disorders, yet, the specific role of Interferon Regulatory Factor 3 (IRF3) in neuroinflammation remains poorly understood. Here, we show that global IRF3 deficiency delays TLR4-mediated signaling in microglia and attenuates the hallmark features of LPS-induced inflammation such as cytokine release, microglial reactivity, astrocyte activation, myeloid cell infiltration, and inflammasome activation. Moreover, expression of a constitutively active IRF3 (S388D/S390D:IRF3-2D) in microglia induces a transcriptional program reminiscent of the Activated Response Microglia and the expression of genes associated with Alzheimer's Disease, notably apolipoprotein-e. Lastly, using bulk-RNAseq of IRF3-2D brain myeloid cells, we identified Z-DNA binding protein-1 as a target of IRF3 that is relevant across various neuroinflammatory disorders. Together, our results identify IRF3 as an important regulator of LPS-mediated neuroinflammatory responses and highlight IRF3 as a central regulator of disease-specific gene activation in different neuroinflammatory diseases

Liraglutide improves liver microvascular dysfunction in cirrhosis: Evidence from translational studies

Hepatic stellate cells (HSC) play a key role in the development of chronic liver disease (CLD). Liraglutide, well-established in type 2 diabetes, showed anti-inflammatory and anti-oxidant properties. We evaluated the effects of liraglutide on HSC phenotype and hepatic microvascular function using diverse pre-clinical models of CLD. Human and rat HSC were in vitro treated with liraglutide, or vehicle, and their phenotype, viability and proliferation were evaluated. In addition, liraglutide or vehicle was administered to rats with CLD. Liver microvascular function, fibrosis, HSC phenotype and sinusoidal endothelial phenotype were determined. Additionally, the effects of liraglutide on HSC phenotype were analysed in human precision-cut liver slices. Liraglutide markedly improved HSC phenotype and diminished cell proliferation. Cirrhotic rats receiving liraglutide exhibited significantly improved liver microvascular function, as evidenced by lower portal pressure, improved intrahepatic vascular resistance, and marked ameliorations in fibrosis, HSC phenotype and endothelial function. The anti-fibrotic effects of liraglutide were confirmed in human liver tissue and, although requiring further investigation, its underlying molecular mechanisms suggested a GLP1-R-independent and NF-κB-Sox9-dependent one. This study demonstrates for the first time that liraglutide improves the liver sinusoidal milieu in pre-clinical models of cirrhosis, encouraging its clinical evaluation in the treatment of chronic liver disease

Neuroblastoma RAS viral oncogene homolog (N-RAS) deficiency aggravates liver injury and fibrosis.

Progressive hepatic damage and fibrosis are major features of chronic liver diseases of different etiology, yet the underlying molecular mechanisms remain to be fully defined. N-RAS, a member of the RAS family of small guanine nucleotide-binding proteins also encompassing the highly homologous H-RAS and K-RAS isoforms, was previously reported to modulate cell death and renal fibrosis; however, its role in liver damage and fibrogenesis remains unknown. Here, we approached this question by using N-RAS deficient (N-RAS-/-) mice and two experimental models of liver injury and fibrosis, namely carbon tetrachloride (CCl4) intoxication and bile duct ligation (BDL). In wild-type (N-RAS+/+) mice both hepatotoxic procedures augmented N-RAS expression in the liver. Compared to N-RAS+/+ counterparts, N-RAS-/- mice subjected to either CCl4 or BDL showed exacerbated liver injury and fibrosis, which was associated with enhanced hepatic stellate cell (HSC) activation and leukocyte infiltration in the damaged liver. At the molecular level, after CCl4 or BDL, N-RAS-/- livers exhibited augmented expression of necroptotic death markers along with JNK1/2 hyperactivation. In line with this, N-RAS ablation in a human hepatocytic cell line resulted in enhanced activation of JNK and necroptosis mediators in response to cell death stimuli. Of note, loss of hepatic N-RAS expression was characteristic of chronic liver disease patients with fibrosis. Collectively, our study unveils a novel role for N-RAS as a negative controller of the progression of liver injury and fibrogenesis, by critically downregulating signaling pathways leading to hepatocyte necroptosis. Furthermore, it suggests that N-RAS may be of potential clinical value as prognostic biomarker of progressive fibrotic liver damage, or as a novel therapeutic target for the treatment of chronic liver disease

Disfunció microcirculatòria sinusoïdal hepàtica en la cirrosi i dany per isquèmia/reperfusió: mecanismes involucrats i noves dianes terapèutiques

[cat] El sinusoide hepàtic és un llit vascular molt especialitzat. La comunicació autocrina i paracrina entre tots els tipus cel·lulars coordina els processos d’inflamació, trombosi i remodelat tissular i determina la correcta regulació del to vascular hepàtic, de manera que en resposta al dany, les cèl·lules sinusoïdals perden el seu fenotip característic i esdevenen pro-trombòtiques, pro- inflamatòries, pro-contràctils i pro-fibròtiques. En aquesta tesi doctoral hem estudiat els mecanismes de dany hepàtic i la regulació de les cèl·lules sinusoïdals durant la cirrosi i la isquèmia/reperfusió en resposta a dos fàrmacs diferents ja aprovats per a l’ús en humans: liraglutida i simvastatina. La liraglutida és un anàleg de la hormona incretina GLP-1 i és emprada en el tractament de la diabetis de tipus II. Estudis previs han demostrat els efectes antiinflamatoris d’aquest fàrmac en la malaltia de fetge gras d’origen no alcohòlic (NAFLD). Com que la inflamació és un factor implicat en l’inici i la progressió de la cirrosi hepàtica, la liraglutida podria tenir efectes protectors en aquest context, essent un fàrmac ràpidament aplicable a la pràctica clínica. Per tant, l’objectiu d’aquest estudi ha estat avaluar els efectes de la liraglutida sobre el fenotip de les cèl·lules estrellades hepàtiques (HSC), la funció microvascular i els seus efectes derivats en models pre-clínics de malaltia hepàtica crònica. Aquests efectes es van estudiar en diferents models de malaltia hepàtica crònica, tant en models de tractament in vitro en HSC cirròtiques aïllades de biòpsies hepàtiques humanes o de rata com en el tractament in vivo en models animals de malaltia hepàtica crònica. La liraglutida va millorar marcadament el fenotip de les HSC i en va reduir la proliferació. Les rates cirròtiques tractades amb liraglutida van mostrar una millora significativa de la funció microvascular, evidenciada per una menor pressió portal, una reducció en la resistència vascular intrahepàtica i millores marcades en la fibrosi, el fenotip de les HSC i la funció endotelial. Els efectes antifibròtics de la liraglutida es van confirmar en teixit humà i, tot i requerir més investigació, aquests efectes serien independents del receptor de GLP-1 i dependents de la via d’NF-kappaB – Sox9. D’altra banda, el factor de transcripció Krüppel-like factor 2 (KLF2), induïble amb simvastatina, confereix vasoprotecció endotelial. Considerant que estudis recents suggereixen que les estatines son capaces d’induir l’autofàgia (mecanisme de supervivència cel·lular), els objectius d’aquest segon estudi van ser: 1) caracteritzar la relació entre l’autofàgia i KLF2 a l’endotelil, 2) estudiar aquesta relació durant el dany hepàtic agut (isquèmia/reperfusió) i 3) estudiar els efectes de la modulació de KLF2-autofàgia in vitro i in vivo. Vam observar una retroalimentació positiva a l’endoteli entre l’autofàgia i KLF2: els activadors de KLF2, tant farmacològics (estatines, resveratrol, GGTI-298) com genètics (adenovirus codificant per KLF2) o fisiològics (estrès per fregament), van causar una sobreexpressió endotelial de KLF2 mitjançant un mecanisme depenent de Rac1-rab7-autofàgia, tant a l’endoteli sinusoïdal hepàtic (LSEC) com a les cèl·lules endotelials vasculars. Al seu torn, la inducció de KLF2 va promoure una activació de l’autofàgia. La isquèmia freda en solució de la Universitat de Wisconsin i la reperfusió van causar la inhibició de la fusió dels autofagosomes amb els lisosomes, mentre que el pretractament amb simvastatina va mantenir el flux autofàgic (incrementant els nivells de Rab7), resultant en la inducció de KLF2 i una millor viabilitat cel·lular i funció microvascular. En conjunt, els resultats obtinguts mostren el potencial prometedor de la liraglutida per al tractament de la cirrosi i ajuden a la comprensió dels mecanismes moleculars de la vasoprotecció mediada per estatines, permetent així proposar noves estratègies terapèutiques per al tractament de les malalties hepàtiques i extrahepàtiques.[eng] The hepatic sinusoid is a highly specialized vascular bed. Autocrine and paracrine communication between all hepatic cell types coordinate inflammation, thrombosis and tissue remodeling, determining the correct regulation of the hepatic vascular tone. As a response to injury, sinusoidal cells lose their characteristic phenotype and become pro-thrombotic, pro- inflammatory, pro-contractile and pro-fibrotic. In this thesis, we have studied the mechanisms of hepatic damage and sinusoidal cells regulation during cirrhosis and ischemia/reperfusion in response to two different drugs that are already approved for human administration: liraglutide and simvastatin. Liraglutide is an analogue of the incretin hormone GLP-1 with anti-inflammatory properties and used for the treatment of type II diabetes. In the first study, we describe for the first time that liraglutide improves the liver sinusoidal milieu in pre-clinical models of cirrhosis, including isolated human hepatic stellate cells or human precision cut liver slices. On the other hand, simvastatin is known for its cholesterol-independent vasoprotective effects which are mediated by induction of the transcription factor KLF2. In addition, simvastatin has recently been described to induce autophagy, which is a cell survival process. In the second study, we describe for the first time the complex autophagy-KLF2 relationship, modulating the phenotype and survival of the endothelium during ischemia/reperfusion. In conclusion, the obtained results show the promising potential of liraglutide for the treatment of cirrhosis and help in the comprehension of the molecular mechanisms of statin-mediated vasoprotection, thus proposing new therapeutic strategies for the treatment of hepatic and extrahepatic diseases

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

Regression of portal hypertension: underlying mechanisms and therapeutic strategies.

Portal hypertension is the main non-neoplastic complication of chronic liver disease, being the cause of important life-threatening events including the development of ascites or variceal bleeding. The primary factor in the development of portal hypertension is a pathological increase in the intrahepatic vascular resistance, due to liver microcirculatory dysfunction, which is subsequently aggravated by extra-hepatic vascular disturbances including elevation of portal blood inflow. Evidence from pre-clinical models of cirrhosis has demonstrated that portal hypertension and chronic liver disease can be reversible if the injurious etiological agent is removed and can be further promoted using pharmacological therapy. These important observations have been partially demonstrated in clinical studies. This paper aims at providing an updated review of the currently available data regarding spontaneous and drug-promoted regression of portal hypertension, paying special attention to the clinical evidence. It also considers pathophysiological caveats that highlight the need for caution in establishing a new dogma that human chronic liver disease and portal hypertension is reversible

Novel therapeutics for portal hypertension and fibrosis in chronic liver disease.

Portal hypertension (PH) is the most common non-neoplastic complication of chronic liver disease, determining clinical complications that lead to death or liver transplantation. PH results from increased resistance to portal blood flow through the cirrhotic liver, which is due to hepatic fibrosis and microcirculatory dysfunction. The present review focuses on the pathophysiology of fibrosis and PH, describes currently used treatments, and critically discusses potential therapeutic options