1 6269 135 THE NEXT CHALLENGE IN PEDIATRIC CHOLESTASIS: DECIPHERING THE PATHOGENESIS OF BILIARY ATRESIA. CHOLESTASIS IS A COMMON PRESENTING SYMPTOM OF LIVER DISEASE IN INFANTS. CHIEF AMONG DISEASES PRESENTING AS NEONATAL CHOLESTASIS IS BILIARY ATRESIA, THE MOST COMMON CAUSE OF CHRONIC LIVER DISEASE IN CHILDREN, BUT LITTLE IS KNOWN ABOUT THE PATHOGENESIS OF THIS DISEASE. IN SEARCH FOR THE MOLECULAR BASIS OF BILIARY ATRESIA, WE BEGAN TWO AREAS OF INVESTIGATION. IN THE FIRST, WE INTERROGATED THE HEPATIC TRANSCRIPTOME OF CHILDREN WITH BILIARY ATRESIA AND FOUND AN INTERFERON-GAMMA (IFNGAMMA)-RICH PROINFLAMMATORY FOOTPRINT AT THE TIME OF DIAGNOSIS. TO DIRECTLY EXPLORE IF IFNGAMMA PLAYS AN IMPORTANT ROLE IN BILIARY INJURY AND OBSTRUCTION, WE USED A MOUSE MODEL OF EXPERIMENTAL BILIARY ATRESIA AND FOUND THAT INACTIVATION OF THE MURINE IFNGAMMA GENE DECREASES THE TROPISM OF LYMPHOCYTES TO NEONATAL BILE DUCTS AND PREVENTS THE INFLAMMATORY OBSTRUCTION OF THE DUCT LUMEN. FURTHER ANALYSIS OF THE EXTRAHEPATIC BILIARY TRACT ALSO OUTLINED A BROADER NETWORK OF PROINFLAMMATORY GENES AT THE ONSET AND DURING PROGRESSION TO DUCT OBSTRUCTION, WITH THE TIME-SPECIFIC ACTIVATION OF IFNGAMMA-, APOPTOSIS-, AND COMPLEMENT-DRIVEN NETWORKS. IN THE SECOND APPROACH, WE SEARCHED FOR MOLECULAR PROFILES THAT DIFFERENTIATE CLINICAL FORMS OF BILIARY ATRESIA BY ANALYZING THE HEPATIC TRANSCRIPTOME OF AGE-MATCHED SUBJECTS AT THE TIME OF DIAGNOSIS. WE FOUND A PRELIMINARY PROFILE THAT DIFFERENTIATES THE EMBRYONIC FROM THE PERINATAL FORMS OF BILIARY ATRESIA. THE PROFILE CONTAINED THE DIFFERENTIAL ACTIVATION OF GENES INVOLVED IN EPIGENETIC MECHANISMS OF DISEASE. COLLECTIVELY, THESE STUDIES PROVIDE NEW INSIGHT INTO PATHOGENESIS OF BILIARY ATRESIA AND IDENTIFY POTENTIAL THERAPEUTIC TARGETS TO FOSTER LONG-TERM OUTCOME WITH THE NATIVE LIVER. 2006 2 6650 33 UPDATE ON ETIOLOGY AND PATHOGENESIS OF BILIARY ATRESIA. BILIARY ATRESIA IS A RARE INFLAMMATORY SCLEROSING OBSTRUCTIVE CHOLANGIOPATHY THAT INITIATES IN INFANCY AS COMPLETE CHOLEDOCHAL BLOCKAGE AND PROGRESSES TO THE INVOLVEMENT OF INTRAHEPATIC BILIARY EPITHELIUM. GROWING EVIDENCE SHOWS THAT BILIARY ATRESIA IS NOT A SINGLE ENTITY WITH A SINGLE ETIOLOGY BUT A PHENOTYPE RESULTING FROM MULTIFACTORIAL EVENTS WHOSE COMMON PATH IS OBLITERATIVE CHOLANGIOPATHY. THE ETIOLOGY OF BILIARY ATRESIA HAS BEEN EXPLAINED AS RESULTING FROM GENETIC VARIANTS, TOXINS, VIRAL INFECTION, CHRONIC INFLAMMATION OR BILE DUCT LESIONS MEDIATED BY AUTOIMMUNITY, ABNORMALITIES IN THE DEVELOPMENT OF THE BILE DUCTS, AND DEFECTS IN EMBRYOGENESIS, ABNORMAL FETAL OR PRENATAL CIRCULATION AND SUSCEPTIBILITY FACTORS. IT IS INCREASINGLY EVIDENT THAT THE GENETIC AND EPIGENETIC PREDISPOSITION COMBINED WITH THE ENVIRONMENTAL FACTORS TO WHICH THE MOTHER IS EXPOSED ARE POTENTIAL TRIGGERS FOR BILIARY ATRESIA. THERE IS ALSO AN INDICATION THAT A PROGRESSIVE THICKENING OF THE ARTERIAL MIDDLE LAYER OCCURS IN THIS DISEASE, SUGGESTIVE OF VASCULAR REMODELING AND DISAPPEARANCE OF THE INTERLOBULAR BILE DUCTS. IT IS SUGGESTED THAT THE HYPOXIA/ISCHEMIA PROCESS CAN AFFECT PORTAL STRUCTURES IN BILIARY ATRESIA AND IS ASSOCIATED WITH BOTH THE EXTENT OF BILIARY PROLIFERATION AND THE THICKENING OF THE MEDIAL LAYER. 2022 3 5220 23 PRIMARY BILIARY CHOLANGITIS: A TALE OF EPIGENETICALLY-INDUCED SECRETORY FAILURE? PRIMARY BILIARY CHOLANGITIS (PBC) IS A CHRONIC CHOLESTATIC LIVER DISEASE ASSOCIATED WITH AUTOIMMUNE-RELATED DESTRUCTION OF SMALL TO MEDIUM SIZE INTRAHEPATIC BILE DUCTS. THE AETIOLOGY OF PBC IS UNKNOWN AND ITS PATHOGENESIS REMAINS OBSCURE. BOTH GENETIC VARIANTS AND ENVIRONMENTAL FACTORS HAVE BEEN LINKED TO INCREASED PBC SUSCEPTIBILITY, WITH OTHER ALTERATIONS KNOWN TO COOPERATE IN DISEASE PATHOBIOLOGY. INCREASING EVIDENCE INDICATES THE PRESENCE OF EPIGENETIC ABNORMALITIES IN PBC, PARTICULARLY ALTERATIONS OF CHOLANGIOCELLULAR MICRORNAS (MIRNAS OR MIRS). THIS REVIEW HIGHLIGHTS AND DISCUSSES THE MOST RELEVANT EPIGENETIC ALTERATIONS FOUND IN PATIENTS WITH PBC, FOCUSING ON THE ROLE OF MIR-506 IN THE PROMOTION OF CHOLESTASIS AND IMMUNE ACTIVATION. 2018 4 5221 25 PRIMARY BILIARY CHOLANGITIS: PATHOGENESIS AND THERAPEUTIC OPPORTUNITIES. PRIMARY BILIARY CHOLANGITIS IS A CHRONIC, SEROPOSITIVE AND FEMALE-PREDOMINANT INFLAMMATORY AND CHOLESTATIC LIVER DISEASE, WHICH HAS A VARIABLE RATE OF PROGRESSION TOWARDS BILIARY CIRRHOSIS. SUBSTANTIAL PROGRESS HAS BEEN MADE IN PATIENT RISK STRATIFICATION WITH THE GOAL OF PERSONALIZED CARE, INCLUDING EARLY ADOPTION OF NEXT-GENERATION THERAPY WITH LICENSED USE OF OBETICHOLIC ACID OR OFF-LABEL FIBRATE DERIVATIVES FOR THOSE WITH INSUFFICIENT BENEFIT FROM URSODEOXYCHOLIC ACID, THE CURRENT FIRST-LINE DRUG. THE DISEASE BIOLOGY SPANS GENETIC RISK, EPIGENETIC CHANGES, DYSREGULATED MUCOSAL IMMUNITY AND ALTERED BILIARY EPITHELIAL CELL FUNCTION, ALL OF WHICH INTERACT AND ARISE IN THE CONTEXT OF ILL-DEFINED ENVIRONMENTAL TRIGGERS. A CURRENT FOCUS OF RESEARCH ON NUCLEAR RECEPTOR PATHWAY MODULATION THAT SPECIFICALLY AND POTENTLY IMPROVES BILIARY EXCRETION, REDUCES INFLAMMATION AND ATTENUATES FIBROSIS IS REDEFINING THERAPY. PATIENTS ARE BENEFITING FROM PHARMACOLOGICAL AGONISTS OF FARNESOID X RECEPTOR AND PEROXISOME PROLIFERATOR-ACTIVATED RECEPTORS. IMMUNOTHERAPY REMAINS A CHALLENGE, WITH A LACK OF TARGET DEFINITION, PLEIOTROPIC IMMUNE PATHWAYS AND AN INTERPLAY BETWEEN HEPATIC IMMUNE RESPONSES AND CHOLESTASIS, WHEREIN BILE ACID-INDUCED INFLAMMATION AND FIBROSIS ARE DOMINANT CLINICALLY. THE MANAGEMENT OF PATIENT SYMPTOMS, PARTICULARLY PRURITUS, IS A NOTABLE GOAL REFLECTED IN THE DEVELOPMENT OF RATIONAL THERAPY WITH APICAL SODIUM-DEPENDENT BILE ACID TRANSPORTER INHIBITORS. 2020 5 3327 39 HISTONE DEACETYLASE 4 PROMOTES CHOLESTATIC LIVER INJURY IN THE ABSENCE OF PROHIBITIN-1. PROHIBITIN-1 (PHB1) IS AN EVOLUTIONARILY CONSERVED PLEIOTROPIC PROTEIN THAT PARTICIPATES IN DIVERSE PROCESSES DEPENDING ON ITS SUBCELLULAR LOCALIZATION AND INTERACTOME. RECENT DATA HAVE INDICATED A DIVERSE ROLE FOR PHB1 IN THE PATHOGENESIS OF OBESITY, CANCER, AND INFLAMMATORY BOWEL DISEASE, AMONG OTHERS. DATA PRESENTED HERE SUGGEST THAT PHB1 IS ALSO LINKED TO CHOLESTATIC LIVER DISEASE. EXPRESSION OF PHB1 IS MARKEDLY REDUCED IN PATIENTS WITH PRIMARY BILIARY CIRRHOSIS AND BILIARY ATRESIA OR WITH ALAGILLE SYNDROME, TWO MAJOR PEDIATRIC CHOLESTATIC CONDITIONS. IN THE EXPERIMENTAL MODEL OF BILE DUCT LIGATION, SILENCING OF PHB1 INDUCED LIVER FIBROSIS, REDUCED ANIMAL SURVIVAL, AND INDUCED BILE DUCT PROLIFERATION. IMPORTANTLY, THE MODULATORY EFFECT OF PHB1 IS NOT DEPENDENT ON ITS KNOWN MITOCHONDRIAL FUNCTION. ALSO, PHB1 INTERACTS WITH HISTONE DEACETYLASE 4 (HDAC4) IN THE PRESENCE OF BILE ACIDS. HENCE, PHB1 DEPLETION LEADS TO INCREASED NUCLEAR HDAC4 CONTENT AND ITS ASSOCIATED EPIGENETIC CHANGES. REMARKABLY, HDAC4 SILENCING AND THE ADMINISTRATION OF THE HDAC INHIBITOR PARTHENOLIDE DURING OBSTRUCTIVE CHOLESTASIS IN VIVO PROMOTE GENOMIC REPROGRAMMING, LEADING TO REGRESSION OF THE FIBROTIC PHENOTYPE IN LIVER-SPECIFIC PHB1 KNOCKOUT MICE. CONCLUSION: PHB1 IS AN IMPORTANT MEDIATOR OF CHOLESTATIC LIVER INJURY THAT REGULATES THE ACTIVITY OF HDAC4, WHICH CONTROLS SPECIFIC EPIGENETIC MARKERS; THESE RESULTS IDENTIFY POTENTIAL NOVEL STRATEGIES TO TREAT LIVER INJURY AND FIBROSIS, PARTICULARLY AS A CONSEQUENCE OF CHRONIC CHOLESTASIS. 2015 6 3012 30 GENETICS AND EPIGENETICS IN THE PATHOGENESIS OF PRIMARY BILIARY CHOLANGITIS. PRIMARY BILIARY CHOLANGITIS (PBC) IS A CHRONIC, SLOWLY PROGRESSIVE CHOLESTATIC AUTOIMMUNE LIVER DISEASE PREDOMINANTLY AFFLICTING WOMEN. PBC IS CHARACTERIZED BY THE PRESENCE OF DISEASE-SPECIFIC ANTIMITOCHONDRIAL ANTIBODIES AND THE HISTOLOGICAL DESTRUCTION OF INTRAHEPATIC BILE DUCTS, WHICH EVENTUALLY LEAD TO CIRRHOSIS AND HEPATIC FAILURE. FORTUNATELY, URSODEOXYCHOLIC ACID THERAPY HAS IMPROVED THE OUTCOME OF THE VAST MAJORITY OF PBC CASES. ALTHOUGH THE ETIOLOGY OF PBC HAS NOT YET BEEN ELUCIDATED, HUMAN LEUKOCYTE ANTIGEN (HLA) CLASS II ALLELES HAVE BEEN CONSISTENTLY ASSOCIATED WITH DISEASE ONSET FOR DECADES. PBC PATIENTS MAY ALSO HAVE GENETICALLY DETERMINED RISK FACTORS IN NON-HLA REGIONS. MEANWHILE, EXPOSURE TO ENVIRONMENTAL FACTORS, SUCH AS INFECTIOUS DISEASES AND HARMFUL CHEMICALS, CAN PRODUCE EPIGENETIC ALTERATIONS IN SOME INDIVIDUALS AND SUBSEQUENT PBC ONSET. IN THIS REVIEW, WE DESCRIBE THE INFLUENCE OF HLA ALLELES AND OTHER GENE POLYMORPHISMS ON PBC ALONG WITH THE RESULTS OF GENOME-WIDE ASSOCIATION STUDIES ON THIS DISEASE AND ITS FUTURE PROSPECTS IN TERMS OF EPIGENETICS. 2018 7 2588 32 EPIGENETICS OF PRIMARY BILIARY CHOLANGITIS. PRIMARY BILIARY CHOLANGITIS (PBC) IS A CHRONIC CHOLESTATIC LIVER DISEASE WITH NON-SUPPURATIVE DESTRUCTION OF THE INTRAHEPATIC BILE DUCTS. THE INTERPLAY OF GENETICS AND ENVIRONMENTAL TRIGGERS CONTRIBUTES TO THE ONSET OF THE DISEASE AND SUBSEQUENTLY RESULTS IN CHOLESTASIS AND PROGRESSIVE FIBROSIS. RECENTLY, GENOME-WIDE ASSOCIATION STUDIES (GWAS) HAVE IDENTIFIED MULTIPLE GENES INFLUENCING THE SUSCEPTIBILITY TO PBC IN HLA AND NON-HLA LOCI. HOWEVER, IT IS ESTIMATED THAT THE KNOWN RISK VARIANTS MERELY ACCOUNT FOR NO MORE THAN 20% OF THE HERITABILITY OF PBC AND CAUSES OF THE REMAINING HERITABILITY REMAIN UNCERTAIN. INCREASING EVIDENCE SUGGESTS THAT THE PRESENCE OF EPIGENETIC ABNORMALITIES MAY EXPLAIN THE "MISSING HERITABILITY" THAT CANNOT BE CAPTURED BY GWAS. AMONG THESE EPIGENETIC MECHANISMS, DNA METHYLATION, HISTONE MODIFICATION, AND NONCODING RNAS (I.E. MIRNA AND LNCRNA) ARE INVOLVED IN THE PATHOGENESIS OF PBC. ADDITIONALLY, TELOMERE DYSREGULATION IN BILIARY EPITHELIAL CELLS (BECS) MAY PLAY A ROLE IN DISEASE ONSET, WHEREAS A DEFICIENCY IN SEX CHROMOSOME AND SKEWED GENE EXPRESSION IN THE X CHROMOSOME MAY TO SOME EXTENT EXPLAIN THE FEMALE DOMINANCE IN PBC. 2020 8 4175 28 MELATONIN PROTECTS CHOLANGIOCYTES FROM OXIDATIVE STRESS-INDUCED PROAPOPTOTIC AND PROINFLAMMATORY STIMULI VIA MIR-132 AND MIR-34. BIOSYNTHESIS OF MELATONIN BY CHOLANGIOCYTES IS ESSENTIAL FOR MAINTAINING THE FUNCTION OF BILIARY EPITHELIUM. HOWEVER, THIS CYTOPROTECTIVE MECHANISM APPEARS TO BE IMPAIRED IN PRIMARY BILIARY CHOLANGITIS (PBC). MIR-132 HAS EMERGED AS A MEDIATOR OF INFLAMMATION IN CHRONIC LIVER DISEASES. THE EFFECT OF MELATONIN ON OXIDATIVE STRESS AND BILE ACID-INDUCED APOPTOSIS WAS ALSO EXAMINED IN CHOLANGIOCYES OVEREXPRESSING MIR506, AS A PBC-LIKE CELLULAR MODEL. IN PBC PATIENTS THE SERUM LEVELS OF MELATONIN WERE FOUND INCREASED IN COMPARISON TO HEALTHY CONTROLS. WHEREAS, IN CHOLANGIOCYTES WITHIN CIRRHOTIC PBC LIVERS THE MELATONIN BIOSYNTHETIC PATHWAY WAS SUBSTANTIALLY SUPPRESSED EVEN THOUGH THE EXPRESSIONS OF MELATONIN RATE-LIMITING ENZYME ARALKYLAMINE N-ACETYLTRANSFERASE (AANAT), AND CK-19 (MARKER OF CHOLANGIOCYTES) WERE ENHANCED. IN CHOLANGIOCYTES EXPOSED TO MITOCHONDRIAL OXIDATIVE STRESS MELATONIN DECREASED THE EXPRESSION OF PROAPOPTOTIC STIMULI (PTEN, BAX, MIR-34), WHICH WAS ACCOMPANIED BY THE INHIBITION OF A PIVOTAL MEDIATOR OF INFLAMMATORY RESPONSE NF-KAPPAB-P65 AND THE ACTIVATION OF ANTIAPOPTOTIC SIGNALING (MIR-132, BCL2). SIMILARLY, MELATONIN REDUCED BILE ACID-INDUCED PROAPOPTOTIC CASPASE 3 AND BIM LEVELS. IN SUMMARY, THE INSUFFICIENT HEPATIC EXPRESSION OF MELATONIN IN PBC PATIENTS MAY PREDISPOSE CHOLANGIOCYTES TO OXIDATIVE STRESS-RELATED DAMAGE. MELATONIN, VIA EPIGENETIC MODULATION, WAS ABLE TO SUPPRESS NF-KAPPAB SIGNALING ACTIVATION AND PROTECT AGAINST BILIARY CELLS APOPTOTIC SIGNALING. 2020 9 2378 26 EPIGENETIC REGULATION OF VASCULAR SMOOTH MUSCLE CELL PHENOTYPE SWITCHING IN ATHEROSCLEROTIC ARTERY REMODELING: A MINI-REVIEW. ATHEROSCLEROSIS IS A CHRONIC INFLAMMATORY DISEASE CHARACTERIZED BY EXTENSIVE REMODELING OF MEDIUM AND LARGE-SIZED ARTERIES. INWARD REMODELING (=LUMEN SHRINKAGE) OF THE VASCULAR WALLS IS THE UNDERLYING CAUSE FOR ISCHEMIA IN TARGET ORGANS. THEREFORE, INWARD REMODELING CAN BE CONSIDERED THE PREDOMINANT FEATURE OF ATHEROSCLEROTIC PATHOLOGY. OUTWARD REMODELING (=LUMEN ENLARGEMENT) IS A PHYSIOLOGICAL RESPONSE COMPENSATING FOR LUMEN SHRINKAGE CAUSED BY NEOINTIMAL HYPERPLASIA, BUT AS A PATHOLOGICAL RESPONSE TO CHANGES IN BLOOD FLOW, OUTWARD REMODELING LEADS TO SUBSTANTIAL ARTERIAL WALL THINNING. THINNED VASCULAR WALLS ARE PRONE TO RUPTURE, AND SUBSEQUENT THROMBUS FORMATION ACCOUNTS FOR THE MAJORITY OF ACUTE CARDIOVASCULAR EVENTS. PATHOLOGICAL REMODELING IS DRIVEN BY INFLAMMATORY CELLS WHICH INDUCE VASCULAR SMOOTH MUSCLE CELLS TO SWITCH FROM QUIESCENT TO A PROLIFERATIVE AND MIGRATORY PHENOTYPE. AFTER DECADES OF INTENSIVE RESEARCH, THE MOLECULAR MECHANISMS OF ARTERIAL REMODELING ARE STARTING TO UNFOLD. IN THIS MINI-REVIEW, WE SUMMARIZE THE CURRENT KNOWLEDGE OF THE EPIGENETIC AND TRANSCRIPTIONAL REGULATION OF VASCULAR SMOOTH MUSCLE CELL PHENOTYPE SWITCHING FROM THE CONTRACTILE TO THE SYNTHETIC PHENOTYPE INVOLVED IN ARTERIAL REMODELING AND DISCUSS POTENTIAL THERAPEUTIC OPTIONS. 2021 10 4483 27 MOLECULAR REGULATION OF MAMMALIAN HEPATIC ARCHITECTURE. THE ESSENTIAL LIVER EXOCRINE AND ENDOCRINE FUNCTIONS REQUIRE A PRECISE SPATIAL ARRANGEMENT OF THE HEPATIC LOBULE CONSISTING OF THE CENTRAL VEIN, PORTAL VEIN, HEPATIC ARTERY, INTRAHEPATIC BILE DUCT SYSTEM, AND HEPATOCYTE ZONATION. THIS ALLOWS BLOOD TO BE CARRIED THROUGH THE LIVER PARENCHYMA SAMPLED BY ALL HEPATOCYTES AND BILE PRODUCED BY THE HEPATOCYTES TO BE CARRIED OUT OF THE LIVER THROUGH THE INTRAHEPATIC BILE DUCT SYSTEM COMPOSED OF CHOLANGIOCYTES. THE MOLECULAR ORCHESTRATION OF MULTIPLE SIGNALING PATHWAYS AND EPIGENETIC FACTORS IS REQUIRED TO SET UP LINEAGE RESTRICTION OF THE BIPOTENTIAL HEPATOBLAST PROGENITOR INTO THE HEPATOCYTE AND CHOLANGIOCYTE CELL LINEAGES, AND TO FURTHER REFINE CELL FATE HETEROGENEITY WITHIN EACH CELL LINEAGE REFLECTED IN THE FUNCTIONAL HETEROGENEITY OF HEPATOCYTES AND CHOLANGIOCYTES. IN ADDITION TO THE COMPLEX MOLECULAR REGULATION, THERE IS A COMPLICATED MORPHOGENETIC CHOREOGRAPHY OBSERVED IN BUILDING THE REFINED HEPATIC EPITHELIAL ARCHITECTURE. GIVEN THE MULTIFACETED MOLECULAR AND CELLULAR REGULATION, IT IS NOT SURPRISING THAT IMPAIRMENT OF ANY OF THESE PROCESSES CAN RESULT IN ACUTE AND CHRONIC HEPATOBILIARY DISEASES. TO ENLIGHTEN THE DEVELOPMENT OF POTENTIAL MOLECULAR AND CELLULAR TARGETS FOR THERAPEUTIC OPTIONS, AN UNDERSTANDING OF HOW THE INTRICATE HEPATIC MOLECULAR AND CELLULAR INTERACTIONS ARE REGULATED IS IMPERATIVE. HERE, WE REVIEW THE SIGNALING PATHWAYS AND EPIGENETIC FACTORS REGULATING HEPATIC CELL LINEAGES, FATES, AND EPITHELIAL ARCHITECTURE. 2019 11 3512 26 IDIOPATHIC PULMONARY FIBROSIS. IDIOPATHIC PULMONARY FIBROSIS IS A DEVASTATING, AGE-RELATED LUNG DISEASE OF UNKNOWN CAUSE THAT HAS FEW TREATMENT OPTIONS. THIS DISEASE WAS ONCE THOUGHT TO BE A CHRONIC INFLAMMATORY PROCESS, BUT CURRENT EVIDENCE INDICATES THAT THE FIBROTIC RESPONSE IS DRIVEN BY ABNORMALLY ACTIVATED ALVEOLAR EPITHELIAL CELLS (AECS). THESE CELLS PRODUCE MEDIATORS THAT INDUCE THE FORMATION OF FIBROBLAST AND MYOFIBROBLAST FOCI THROUGH THE PROLIFERATION OF RESIDENT MESENCHYMAL CELLS, ATTRACTION OF CIRCULATING FIBROCYTES, AND STIMULATION OF THE EPITHELIAL TO MESENCHYMAL TRANSITION. THE FIBROBLAST AND MYOFIBROBLAST FOCI SECRETE EXCESSIVE AMOUNTS OF EXTRACELLULAR MATRIX, MAINLY COLLAGENS, RESULTING IN SCARRING AND DESTRUCTION OF THE LUNG ARCHITECTURE. THE MECHANISMS THAT LINK IDIOPATHIC PULMONARY FIBROSIS WITH AGEING AND ABERRANT EPITHELIAL ACTIVATION ARE UNKNOWN; EVIDENCE SUGGESTS THAT THE ABNORMAL RECAPITULATION OF DEVELOPMENTAL PATHWAYS AND EPIGENETIC CHANGES HAVE A ROLE. IN THIS SEMINAR, WE REVIEW RECENT DATA ON THE CLINICAL COURSE, THERAPEUTIC OPTIONS, AND UNDERLYING MECHANISMS THOUGHT TO BE INVOLVED IN THE PATHOGENESIS OF IDIOPATHIC PULMONARY FIBROSIS. 2011 12 2936 36 GENETIC AND EPIGENETIC ABNORMALITIES IN PRIMARY SCLEROSING CHOLANGITIS-ASSOCIATED CHOLANGIOCARCINOMA. PRIMARY SCLEROSING CHOLANGITIS (PSC) IS A CHOLESTATIC LIVER DISEASE OF UNKNOWN ETIOLOGY, CHARACTERIZED BY CHRONIC INFLAMMATION OF THE BILIARY TREE WITH SUBSEQUENT FIBROSIS AND CIRRHOSIS OF THE LIVER. PATIENTS WITH PSC ARE AT INCREASED RISK FOR THE DEVELOPMENT OF CHOLANGIOCARCINOMA (CCA), A HIGHLY MALIGNANT EPITHELIAL TUMOR ARISING FROM THE INTRAHEPATIC AND EXTRAHEPATIC BILE DUCTS. CURRENTLY, ORTHOTOPIC LIVER TRANSPLANTATION IS THE ONLY CURATIVE TREATMENT. THE LACK OF EFFICIENT DIAGNOSTIC METHODS FOR EARLY DETECTION AND THE LIMITED THERAPEUTIC OPTIONS FOR CCA ARE MAJOR PROBLEMS AND ARE ASSOCIATED WITH POOR SURVIVAL. THE PATHOGENESIS OF PSC-ASSOCIATED CCA IS COMPLEX AND POORLY UNDERSTOOD. IT SEEMS THAT PRO-INFLAMMATORY CYTOKINES PLAY AN IMPORTANT ROLE IN GENETIC AND EPIGENETIC CHANGES THAT CONTRIBUTE TO THE CARCINOGENIC PROCESS. THE MAPPING OF GENETIC ALTERATIONS MAY ELUCIDATE MOLECULAR TARGETS THAT MAY BE APPLIED AS BIOMARKERS TO FACILITATE EARLY DIAGNOSIS OF MALIGNANT DEGENERATION TO IMPROVE PATIENT OUTCOME. IN THE LAST DECADE, THE INTRODUCTION OF SEVERAL NOVEL MOLECULAR TECHNIQUES AVAILABLE FOR GENOME-WIDE SCREENING HAS ADVANCED OUR KNOWLEDGE ON MANY OF THE GENETIC ABNORMALITIES THAT ARE PREVALENT IN CCA AND PSC-ASSOCIATED CCA. THIS REVIEW SUMMARIZES GENETIC AND EPIGENETIC ABNORMALITIES, WHICH HAVE IMPORTANT POTENTIAL FOR CLINICAL APPLICATION. 2013 13 3931 22 LIVER INJURY AND THE ACTIVATION OF THE HEPATIC MYOFIBROBLASTS. LIVER FIBROSIS IS A WOUND HEALING PROCESS, THE END RESULT OF CHRONIC LIVER INJURY ELICITED BY DIFFERENT NOXIOUS STIMULI. ACTIVATED HEPATIC STELLATE CELLS OR MYOFIBROBLASTS AND PORTAL MYOFIBROBLASTS ARE CONSIDERED AS THE MAIN PRODUCERS OF THE EXTRACELLULAR MATRIX IN THE LIVER. UPON LIVER INJURY THE QUIESCENT STELLATE CELLS TRANSDIFFERENTIATE INTO MYOFIBROBLASTS A PROCESS HIGHLIGHTED BY THE LOSS OF VITAMIN A STORES, UPREGULATION OF INTERSTITIAL TYPE COLLAGENS, SMOOTH MUSCLE ALPHA ACTIN, MATRIX METALLOPROTEINASES, PROTEOGLYCANS, AND THE INDUCTION OF CELL SURVIVAL PATHWAYS. ACTIVATION OF HEPATIC STELLATE CELLS IS A RESULT OF A COMPLEX INTERPLAY BETWEEN THE PARENCHYMAL CELLS, IMMUNE CELLS, EXTRACELLULAR MATRIX MECHANICS AND EXTRAHEPATIC MILIEU SUCH AS THE GUT MICROBIOME. IN THIS REVIEW WE WILL FOCUS ON THE PATHOMECHANISM OF STELLATE CELL ACTIVATION FOLLOWING CHRONIC LIVER INJURY; WITH THE AIM OF IDENTIFYING POSSIBLE TREATMENT TARGETS FOR ANTI-FIBROGENIC AGENTS. 2013 14 5329 35 PURINERGIC SIGNALING IN THE LUMEN OF A NORMAL NEPHRON AND IN REMODELED PKD ENCAPSULATED CYSTS. THE NEPHRON IS THE FUNCTIONAL UNIT OF THE KIDNEY. BLOOD AND PLASMA ARE CONTINUALLY FILTERED WITHIN THE GLOMERULI THAT BEGIN EACH NEPHRON. ADENOSINE 5' TRIPHOSPHATE (ATP) AND ITS METABOLITES ARE FREELY FILTERED BY EACH GLOMERULUS AND ENTER THE LUMEN OF EACH NEPHRON BEGINNING AT THE PROXIMAL CONVOLUTED TUBULE (PCT). FLOW RATE, OSMOLALITY, AND OTHER MECHANICAL OR CHEMICAL STIMULI FOR ATP SECRETION ARE PRESENT IN EACH NEPHRON SEGMENT. THESE ATP-RELEASE STIMULI ARE ALSO DIFFERENT IN EACH NEPHRON SEGMENT DUE TO WATER OR SALT PERMEABILITY OR IMPERMEABILITY ALONG DIFFERENT LUMINAL MEMBRANES OF THE CELLS THAT LINE EACH NEPHRON SEGMENT. EACH OF THE ABOVE STIMULI CAN TRIGGER ADDITIONAL ATP RELEASE INTO THE LUMEN OF A NEPHRON SEGMENT. EACH NEPHRON-LINING EPITHELIAL CELL IS A POTENTIAL SOURCE OF SECRETED ATP. TOGETHER WITH FILTERED ATP AND ITS METABOLITES DERIVED FROM THE GLOMERULUS, SECRETED ATP AND ADENOSINE DERIVED FROM CELLS ALONG THE NEPHRON ARE LIKELY THE PRINCIPAL TWO OF SEVERAL NUCLEOTIDE AND NUCLEOSIDE CANDIDATES FOR RENAL AUTOCRINE AND PARACRINE LIGANDS WITHIN THE TUBULAR FLUID OF THE NEPHRON. THIS MINIREVIEW DISCUSSES THE FIRST PRINCIPLES OF PURINERGIC SIGNALING AS THEY RELATE TO THE NEPHRON AND THE URINARY BLADDER. THE REVIEW DISCUSSES HOW THE LUMEN OF A RENAL TUBULE PRESENTS AN IDEAL PURINERGIC SIGNALING MICROENVIRONMENT. THE REVIEW ALSO ILLUSTRATES HOW REMODELED AND ENCAPSULATED CYSTS IN AUTOSOMAL DOMINANT POLYCYSTIC KIDNEY DISEASE (ADPKD) AND REMODELED PSEUDOCYSTS IN AUTOSOMAL RECESSIVE PKD (ARPKD) OF THE RENAL COLLECTING DUCT LIKELY CREATE AN EVEN MORE IDEAL MICROENVIRONMENT FOR PURINERGIC SIGNALING. ONCE TRAPPED IN THESE CLOSED MICROENVIRONMENTS, PURINERGIC SIGNALING BECOMES CHRONIC AND LIKELY PLAYS A SIGNIFICANT EPIGENETIC AND DETRIMENTAL ROLE IN THE SECONDARY PROGRESSION OF PKD, ONCE THE REMODELING OF THE RENAL TISSUE HAS BEGUN. IN PKD CYSTIC MICROENVIRONMENTS, WE ARGUE THAT NORMAL PURINERGIC SIGNALING WITHIN THE LUMEN OF THE NEPHRON PROVIDES DETRIMENTAL ACCELERATION OF ADPKD ONCE REMODELING IS COMPLETE. 2008 15 4472 38 MOLECULAR PATHOGENESIS OF CHOLANGIOCARCINOMA. BACKGROUND: CHOLANGIOCARCINOMAS ARE A HETEROGENEOUS GROUP OF MALIGNANCIES ARISING FROM A NUMBER OF CELLS OF ORIGIN ALONG THE BILIARY TREE. ALTHOUGH MOST CASES IN WESTERN COUNTRIES ARE SPORADIC, LARGE POPULATION-BASED STUDIES HAVE IDENTIFIED A NUMBER OF RISK FACTORS. THIS REVIEW SUMMARISES THE EVIDENCE BEHIND REPORTED RISK FACTORS AND CURRENT UNDERSTANDING OF THE MOLECULAR PATHOGENESIS OF CHOLANGIOCARCINOMA, WITH A FOCUS ON INFLAMMATION AND CHOLESTASIS AS THE DRIVING FORCES IN CHOLANGIOCARCINOMA DEVELOPMENT. RISK FACTORS FOR CHOLANGIOCARCINOGENESIS: CHOLESTATIC LIVER DISEASES (E.G. PRIMARY SCLEROSING CHOLANGITIS AND FIBROPOLYCYSTIC LIVER DISEASES), LIVER CIRRHOSIS, AND BILIARY STONE DISEASE ALL INCREASE THE RISK OF CHOLANGIOCARCINOMA. CERTAIN BACTERIAL, VIRAL OR PARASITIC INFECTIONS SUCH AS HEPATITIS B AND C AND LIVER FLUKES ALSO INCREASE CHOLANGIOCARCINOMA RISK. OTHER RISK FACTORS INCLUDE INFLAMMATORY DISORDERS (SUCH AS INFLAMMATORY BOWEL DISEASE AND CHRONIC PANCREATITIS), TOXINS (E.G. ALCOHOL AND TOBACCO), METABOLIC CONDITIONS (DIABETES, OBESITY AND NON-ALCOHOLIC FATTY LIVER DISEASE) AND A NUMBER OF GENETIC DISORDERS. MOLECULAR PATHOGENESIS OF CHOLANGIOCARCINOMA: REGARDLESS OF AETIOLOGY, MOST RISK FACTORS CAUSE CHRONIC INFLAMMATION OR CHOLESTASIS. CHRONIC INFLAMMATION LEADS TO INCREASED EXPOSURE OF CHOLANGIOCYTES TO THE INFLAMMATORY MEDIATORS INTERLEUKIN-6, TUMOUR NECROSIS FACTOR-A, CYCLO-OXYGENASE-2 AND WNT, RESULTING IN PROGRESSIVE MUTATIONS IN TUMOUR SUPPRESSOR GENES, PROTO-ONCOGENES AND DNA MISMATCH-REPAIR GENES. ACCUMULATING BILE ACIDS FROM CHOLESTASIS LEAD TO REDUCED PH, INCREASED APOPTOSIS AND ACTIVATION OF ERK1/2, AKT AND NF-KAPPAB PATHWAYS THAT ENCOURAGE CELL PROLIFERATION, MIGRATION AND SURVIVAL. OTHER MEDIATORS UPREGULATED IN CHOLANGIOCARCINOMA INCLUDE TRANSFORMING GROWTH FACTOR-BETA, VASCULAR ENDOTHELIAL GROWTH FACTOR, HEPATOCYTE GROWTH FACTOR AND SEVERAL MICRORNAS. INCREASED EXPRESSION OF THE CELL SURFACE RECEPTOR C-MET, THE GLUCOSE TRANSPORTER GLUT-1 AND THE SODIUM IODIDE SYMPORTER LEAD TO TUMOUR GROWTH, ANGIOGENESIS AND CELL MIGRATION. STROMAL CHANGES ARE ALSO OBSERVED, RESULTING IN ALTERATIONS TO THE EXTRACELLULAR MATRIX COMPOSITION AND RECRUITMENT OF FIBROBLASTS AND MACROPHAGES THAT CREATE A MICROENVIRONMENT PROMOTING CELL SURVIVAL, INVASION AND METASTASIS. CONCLUSION: REGARDLESS OF AETIOLOGY, MOST RISK FACTORS FOR CHOLANGIOCARCINOMA CAUSE CHRONIC INFLAMMATION AND/OR CHOLESTASIS, LEADING TO THE ACTIVATION OF COMMON INTRACELLULAR PATHWAYS THAT RESULT IN REACTIVE CELL PROLIFERATION, GENETIC/EPIGENETIC MUTATIONS AND CHOLANGIOCARCINOGENESIS. AN UNDERSTANDING OF THE MOLECULAR PATHOGENESIS OF CHOLANGIOCARCINOMA IS VITAL WHEN DEVELOPING NEW DIAGNOSTIC BIOMARKERS AND TARGETED THERAPIES FOR THIS DISEASE. 2019 16 5506 30 RHEUMATOID ARTHRITIS AND PRIMARY BILIARY CIRRHOSIS: CAUSE, CONSEQUENCE, OR COINCIDENCE? PRIMARY BILIARY CIRRHOSIS (PBC) IS A PROGRESSIVE CHOLESTATIC LIVER DISEASE CHARACTERIZED SEROLOGICALLY BY CHOLESTASIS AND THE PRESENCE OF HIGH-TITRE ANTIMITOCHONDRIAL ANTIBODIES AND HISTOLOGICALLY BY CHRONIC NONSUPPURATIVE CHOLANGITIS AND GRANULOMATA. PBC PATIENTS OFTEN HAVE CONCOMITANT AUTOIMMUNE DISEASES, INCLUDING ARTHROPATHIES. THIS RAISES THE QUESTION AS TO WHETHER THERE ARE SHARED FEATURES IN THE PATHOGENESIS OF THOSE DISEASES WITH THE PATHOGENESIS OF PBC. EPIDEMIOLOGICAL AND LARGE CASE STUDIES HAVE INDICATED THAT ALTHOUGH THE INCIDENCE OF RHEUMATOID ARTHRITIS (RA) IS NOT SIGNIFICANTLY RAISED IN PBC PATIENTS, THERE APPEARS TO BE A HIGHER RATE OF RA IN PBC PATIENTS AND THEIR RELATIVES. GENETIC STUDIES HAVE DEMONSTRATED THAT SEVERAL GENES IMPLICATED IN PBC HAVE ALSO BEEN IMPLICATED IN RA. EPIGENETIC STUDIES PROVIDED A WEALTH OF DATA REGARDING RA, BUT THE FINDINGS ON EPIGENETIC CHANGES IN PBC ARE VERY LIMITED. AS WELL, CERTAIN INFECTIOUS AGENTS IDENTIFIED IN THE PATHOGENESIS OF PBC MAY ALSO PLAY A ROLE IN THE PATHOGENESIS OF RA. THESE DATA SUGGEST THAT ALTHOUGH RA IS NOT SIGNIFICANTLY PRESENT IN PBC, SOME INDIVIDUALS WITH CERTAIN GENETIC TRAITS AND ENVIRONMENTAL EXPOSURES MAY DEVELOP BOTH CONDITIONS. THIS CONCEPT MAY ALSO APPLY TO OTHER CONCOMITANT DISEASES FOUND IN PBC PATIENTS. 2012 17 3674 24 INFLAMMATION AND DYSREGULATED FIBROBLAST PROLIFERATION--NEW MECHANISMS? IDIOPATHIC PULMONARY FIBROSIS (IPF) IS A DEVASTATING, AGE-RELATED LUNG DISEASE OF UNKNOWN CAUSE THAT HAS FEW TREATMENT OPTIONS. ONCE THOUGHT TO BE A CHRONIC INFLAMMATORY PROCESS, CURRENT EVIDENCE INDICATES THAT THE FIBROTIC RESPONSE MAY PRIMARILY BE DRIVEN BY ABNORMALLY ACTIVATED ALVEOLAR EPITHELIAL CELLS AND THE UNDERLYING MESENCHYME. THE MEDIATORS PRODUCED AND PRESENT IN THIS MICROENVIRONMENT INDUCE THE FORMATION OF FIBROBLAST FOCI THROUGH THE PROLIFERATION OF RESIDENT MESENCHYMAL CELLS, ATTRACTION OF CIRCULATING FIBROCYTES, AND STIMULATION OF EPITHELIAL TO MESENCHYMAL TRANSITION. THE FIBROBLAST AND MYOFIBROBLAST FOCI SECRETE EXCESSIVE AMOUNTS OF EXTRACELLULAR MATRIX, MAINLY COLLAGENS, RESULTING IN SCARRING AND DESTRUCTION OF THE LUNG ARCHITECTURE. THE DETAILED MECHANISMS THAT LINK IPF WITH AGEING AND ABERRANT EPITHELIAL ACTIVATION ARE UNKNOWN, BUT SOME EVIDENCE SUGGESTS THAT THE ABNORMAL RECAPITULATION OF DEVELOPMENTAL PATHWAYS AND EPIGENETIC CHANGES MAY PLAY A ROLE. THIS REVIEW PROVIDES A BRIEF SYNOPSIS OF HIGHLIGHTS IN THE CURRENT UNDERSTANDING OF THE PATHOPHYSIOLOGY OF IPF, AS WELL AS NOVEL THERAPEUTICS BEING EXPLORED IN CLINICAL TRIALS FOR THE TREATMENT OF THIS DEVASTATING DISEASE. 2013 18 6053 23 THE CRUCIAL ROLE OF NLRP3 INFLAMMASOME IN VIRAL INFECTION-ASSOCIATED FIBROSING INTERSTITIAL LUNG DISEASES. IDIOPATHIC PULMONARY FIBROSIS (IPF), ONE OF THE MOST COMMON FIBROSING INTERSTITIAL LUNG DISEASES (ILD), IS A CHRONIC-AGE-RELATED RESPIRATORY DISEASE THAT RISES FROM REPEATED MICRO-INJURY OF THE ALVEOLAR EPITHELIUM. ENVIRONMENTAL INFLUENCES, INTRINSIC FACTORS, GENETIC AND EPIGENETIC RISK FACTORS THAT LEAD TO CHRONIC INFLAMMATION MIGHT BE IMPLICATED IN THE DEVELOPMENT OF IPF. THE EXACT TRIGGERS THAT INITIATE THE FIBROTIC RESPONSE IN IPF REMAIN ENIGMATIC, BUT THERE IS NOW INCREASING EVIDENCE SUPPORTING THE ROLE OF CHRONIC EXPOSURE OF VIRAL INFECTION. DURING VIRAL INFECTION, ACTIVATION OF THE NLRP3 INFLAMMASOME BY INTEGRATING MULTIPLE CELLULAR AND MOLECULAR SIGNALING IMPLICATES ROBUST INFLAMMATION, FIBROBLAST PROLIFERATION, ACTIVATION OF MYOFIBROBLAST, MATRIX DEPOSITION, AND ABERRANT EPITHELIAL-MESENCHYMAL FUNCTION. OVERALL, THE CROSSTALK OF THE NLRP3 INFLAMMASOME AND VIRUSES CAN ACTIVATE IMMUNE RESPONSES AND INFLAMMASOME-ASSOCIATED MOLECULES IN THE DEVELOPMENT, PROGRESSION, AND EXACERBATION OF IPF. 2021 19 5140 22 POTENTIAL REGULATORS OF THE SENESCENCE-ASSOCIATED SECRETORY PHENOTYPE DURING SENESCENCE AND AGING. SENESCENT CELLS EXPRESS AND SECRETE A VARIETY OF EXTRACELLULAR MODULATORS THAT INCLUDE CYTOKINES, CHEMOKINES, PROTEASES, GROWTH FACTORS, AND SOME ENZYMES ASSOCIATED WITH EXTRACELLULAR MATRIX REMODELING, DEFINED AS THE SENESCENCE-ASSOCIATED SECRETORY PHENOTYPE (SASP). SASP REINFORCES SENESCENT CELL CYCLE ARREST, STIMULATES AND RECRUITS IMMUNE CELLS FOR IMMUNE-MEDIATED CLEARANCE OF POTENTIALLY TUMORIGENIC CELLS, LIMITS OR INDUCES FIBROSIS, AND PROMOTES WOUND HEALING AND TISSUE REGENERATION. ON THE OTHER HAND, SASP MEDIATES CHRONIC INFLAMMATION LEADING TO THE DESTRUCTION OF TISSUE STRUCTURE AND FUNCTION AND STIMULATING THE GROWTH AND SURVIVAL OF TUMOR CELLS. SASP IS HIGHLY HETEROGENEOUS AND THE ROLE OF SASP DEPENDS ON THE CONTEXT. THE REGULATION OF SASP OCCURS AT MULTIPLE LEVELS INCLUDING CHROMATIN REMODELING, TRANSCRIPTION, MRNA TRANSLATION, INTRACELLULAR TRAFFICKING, AND SECRETION. SEVERAL SASP MODULATORS HAVE ALREADY BEEN IDENTIFIED SETTING THE STAGE FOR FUTURE RESEARCH ON THEIR CLINICAL APPLICATIONS. IN THIS REVIEW, WE SUMMARIZE IN DETAIL THE POTENTIAL SIGNALING PATHWAYS THAT TRIGGER AND REGULATE SASP PRODUCTION DURING AGING AND SENESCENCE. 2022 20 5590 30 ROLE OF THE BICARBONATE-RESPONSIVE SOLUBLE ADENYLYL CYCLASE IN CHOLANGIOCYTE APOPTOSIS IN PRIMARY BILIARY CHOLANGITIS; A NEW HYPOTHESIS. PRIMARY BILIARY CHOLANGITIS (PBC) IS A CHRONIC FIBROSING CHOLANGIOPATHY CHARACTERIZED BY AN AUTOIMMUNE STEREOTYPE AND DEFECTIVE BILIARY BICARBONATE SECRETION DUE TO DOWN-REGULATION OF ANION EXCHANGER 2 (AE2). DESPITE THE AUTOIMMUNE FEATURES, IMMUNOSUPPRESSANTS ARE INEFFECTIVE WHILE TWO BILE ACID-BASED THERAPIES (URSODEOXYCHOLIC ACID AND OBETICHOLIC ACID) HAVE BEEN SHOWN TO IMPROVE BIOCHEMICAL AND HISTOLOGICAL FEATURES OF CHOLESTASIS AND LONG-TERM PROGNOSIS. HOWEVER, THE ETIOLOGY AND PATHOGENESIS OF PBC IS LARGELY UNKNOWN. RECENTLY, IT HAS BEEN SHOWN THAT MICRORNA-506 (MIR-506) ON CHROMOSOME X IS UP-REGULATED IN PBC CHOLANGIOCYTES AND SUPPRESSES AE2 EXPRESSION, WHICH SENSITIZES CHOLANGIOCYTES TO BILE SALT-INDUCED APOPTOSIS BY ACTIVATING SOLUBLE ADENYLYL CYCLASE (SAC), AN EVOLUTIONARILY CONSERVED BICARBONATE SENSOR. IN THIS REVIEW, WE DISCUSS THE EXPERIMENTAL EVIDENCE FOR THE EMERGING ROLE OF THE MIR-506-AE2-SAC AXIS IN PBC PATHOGENESIS. WE FURTHER HYPOTHESIZE THAT THE INITIAL DISEASE TRIGGER INDUCES AN X-LINKED EPIGENETIC CHANGE, LEADING TO A FEMALE-BIASED ACTIVATION OF THE MIR-506-AE2-SAC AXIS. THIS ARTICLE IS PART OF A SPECIAL ISSUE ENTITLED: CHOLANGIOCYTES IN HEALTH AND DISEASEEDITED BY JESUS BANALES, MARCO MARZIONI AND PETER JANSEN. 2018