Mapping of a disease susceptibility locus in the HLA region for Primary Biliary Cirrhosis in Japan

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.

Tumour necrosis factor alpha (TNF-α) genetic polymorphisms and the risk of autoimmune liver disease: a meta-analysis

Epidemiological studies have evaluated the association between tumour necrosis factor alpha (TNF-α)- 308G/A and (TNF-α)- 238G/A polymorphisms, and the risk of autoimmune liver disease (AILD), yet the results are conflicting. To derive a more precise estimation of the relationship, we performed this meta-analysis. A systematic review was conducted to identify all eligible studies of TNF-α polymorphisms and AILD risk. We used odds ratios (ORs) with 95% confidence intervals (CIs) to assess the strength of the association between the two TNF-α polymorphisms and AILD risk. A total of 15 eligible studies were identified. Overall, positive associations of -308G/A polymorphism with AILD risk were found (A vs G allele: OR =1.45, 95%CI = 1.13- 1.86; AA vs GG: OR = 2.74, 95%CI = 1.51- 4.96; GA vs GG: OR = 1.46, 95%CI = 1.11- 1.92;dominant model: OR = 1.57, 95%CI = 1.18- 2.10; recessive model: OR = 2.22, 95%CI = 1.31- 3.76). In subgroup analysis by ethnicity, a significantly higher risk was found in Caucasians. In subgroup analysis by AILD category, significant association was observed in autoimmune hepatitis and primary sclerosing cholangitis, especially in Caucasians. Patients carrying TNF-α-238A allele had a slightly decreased risk of developing AILD (OR = 0.65, 95%CI = 0.48- 0.87). However, we found both TNF-α polymorphisms were not associated with primary biliary cirrhosis risk, even in subgroup analysis. Our meta-analysis suggests that the TNF-α-308G/A and -238G/A polymorphisms may contribute to AILD susceptibility in Caucasians,especially for autoimmune hepatitis and primary sclerosing cholangitis. Nevertheless, we found both TNF-α polymorphisms were unlikely to be associated with the risk of primary biliary cirrhosis

Treatment of Primary Biliary Cirrhosis: A new challenge?

Primary biliary cirrhosis (PBC) is characterized by unknown etiologies, anti-mitochondrial antibodies, injury of the biliary duct and the lack of a definite remedy. The etiologies of PBC have been well-discussed, including microorganisms and xenobiotics as the triggers for initiating the disease, and an abnormality of immune-tolerance. Recently, several animal models of PBC have been developed that may lead to the development of new therapies. Here, we reviewed the articles that address the etiology of PBC and the therapy for this disease for the confirmation of our current positions and future directions.

TNF-alpha polymorphisms in primary biliary cirrhosis: a northern and southern Italian experience

Specific HLA alleles and immunoregulatory genes have been evaluated in primary biliary cirrhosis (PBC), but data are discordant. We determined whether TNF-alpha promoter polymorphisms (G-308A and G-238A) and alleles of HLA class II (HLA-DRB1) might be associated either with PBC occurrence and severity in Italian populations from two distinct areas. The distribution of TNF1 (G/G) genotype did not differ either between patients and controls or between patients from Northern and Southern Italy. Contrariwise, the HLA-DRB1*08 appeared positively linked to the occurrence of disease (8.4% in patients vs. 2.5% in controls, P = 0.003), whereas the HLA-DRB1*13 appeared to be protective, being more frequent in controls (12.8%) than in patients (7%) (P = 0.038). Neither positively nor negatively associated alleles of the two genomic loci had an effect on disease progression. We report a distinct genetic risk of developing PBC in the Italian population, with no interaction between the HLA and TNF alleles.

Genetics and genomics of primary biliary cirrhosis

The etiologic and pathogenic factors contributing to primary biliary cirrhosis (PBC) development, progression, response to treatment, and outcome remain a mystery. Recognition of the genomic regions harboring risk factors is hindered by the rarity and late onset of PBC. Recent advancements in genomics hold promise for understanding, prevention, and therapy of PBC. Large registries and biospecimen repositories of patients who have PBC, their family members, and controls are needed. Haplotype mapping-based association studies are necessary for defining genetic predisposition. Experimental data will provide the means for fine mapping studies, resequencing efforts, functional experimentation, and elucidation of gene-environment and gene-gene interaction.