1. Ah receptor mediating induction of cytochrome P450IA1 in a novel continuous human liver cell line (Mz-Hep-1). Detection by binding with [3H]2,3,7,8-tetrachlorodibenzo-p-dioxin and relationship to the activity of aryl hydrocarbon hydroxylase
W G Dippold, E A Roberts, K C Johnson Biochem Pharmacol . 1991 Jul 15;42(3):521-8. doi: 10.1016/0006-2952(91)90314-u.
The Ah receptor regulates induction of cytochrome P450IA1 and mediates certain toxicities of polyhalogenated aromatics such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). It has been characterized previously in continuous cell lines, notably the mouse hepatoma line Hepa 1, the human squamous cell carcinoma line A431, and the human liver cell line Hep G2. The present work extends our knowledge of the Ah receptor in continuous human liver cell lines. Ah receptor can be detected in Mz-Hep-1, a hepatitis B virus-negative cell line derived from a Thorotrast-induced hepatocellular carcinoma. The mean concentration of Ah receptor in Mz-Hep-1 cells was 341 +/- 22 fmol/mg cytosol protein (mean +/- SEM, nine separate determinations). This is equivalent to approximately 30,000 sites per cell. The concentration of Ah receptor in Mz-Hep-1 cells is similar to that in Hepa 1 cells and approximately three times higher than that in Hep G2 cells. The Mz-Hep-1 Ah receptor sedimented in continuous sucrose gradients at approximately 9 S. Specificity of binding by [3H]TCDD was demonstrated by competitive binding of non-radiolabeled 2,3,7,8-tetrachlorodibenzofuran, 3-methylcholanthrene (MC), and dibenz[a,h]anthracene in 50-fold molar excess. Phenobarbital, which is not a substrate for P450IA1, did not compete with [3H]TCDD for binding to Mz-Hep-1 Ah receptor. Dexamethasone and estradiol also did not compete with [3H]TCDD for binding, suggesting non-identity of Ah receptor with glucocorticoid or estrogen receptor. In separate experiments, glucocorticoid receptor was identified in Mz-Hep-1 cells. By Scatchard plot analysis, the apparent equilibrium dissociation constant (Kd) for binding of [3H]TCDD to Mz-Hep-1 Ah receptor was estimated to be 4.4 nM, compared to 0.8 nM in Hepa 1 cells. By Woolf plot analysis the Kd was 5.4 nM, compared to 1.2 nM in Hepa 1 cells. The [3H]TCDD.Ah receptor complex extracted from nuclei of Mz-Hep-1 cells incubated with [3H]TCDD in culture at 37 degrees sedimented at approximately 6 S under conditions of high ionic strength. Aryl hydrocarbon hydroxylase (AHH) activity was detectable in Mz-Hep-1 cells after pretreatment with inducing chemicals. Mz-Hep-1 cells have the highest concentrations of Ah receptor in any continuous human liver cell line thus far investigated. The Mz-Hep-1 Ah receptor is similar physicochemically to that described in murine systems. AHH activity is inducible in Mz-Hep-1 cells.
2. Heterozygous MZ alpha-1-antitrypsin deficiency in adults with chronic liver disease
E Schrumpf, M K Fagerhol, H Bell Scand J Gastroenterol . 1990 Aug;25(8):788-92. doi: 10.3109/00365529008999216.
Pi phenotype was determined in 335 patients with liver diseases and compared with the results in 2830 healthy blood donors. Eleven of 335 patients had phenotype MZ (3.3%, compared with 2.9% in healthy blood donors (NS]. None of 53 patients with autoimmune chronic active hepatitis had the MZ phenotype, but it was found in 2 of 18 patients (11.1%) with cryptogenic cirrhosis, 3 of 78 (3.8%) with alcoholic liver cirrhosis, 2 of 36 (5.6%) with primary sclerosing cholangitis, and 1 of 26 (3.9%) with primary biliary cirrhosis. Altogether, 3 of 335 patients were homozygous for Pi ZZ and had cirrhosis. One of them (a male) developed a hepatoma and died. We conclude that the reported association between Pi MZ phenotype and chronic non-B active hepatitis does not seem to include patients with autoimmune chronic active hepatitis, whereas the possibility of an association between cryptogenic cirrhosis and the MZ phenotype cannot be excluded.
3. Alpha-1-Antitrypsin Pi*MZ Variant Increases Risk of Developing Hepatic Events in Nonalcoholic Fatty Liver Disease Patients
Arvind R Murali, Antonio J Sanchez, Sameer Prakash Clin Res Hepatol Gastroenterol . 2022 Dec 9;102066. doi: 10.1016/j.clinre.2022.102066.
Aims:Heterozygous alpha-1-antitrypsin (A1AT) Pi*MZ variant has been shown to increase the risk of developing liver cirrhosis in patients with non-alcoholic fatty liver disease (NAFLD). We aimed to determine the association between heterozygous Pi*MZ and Pi*MS variants and development of hepatic decompensation events in NAFLD patients.Methods:We included patients with NAFLD who also had A1AT genotyping performed from 2005-2020. We recorded demographic and clinical variables, and data on hepatic events (ascites, hepatic encephalopathy, esophageal variceal bleed, or hepatocellular carcinoma), if any. We performed binary logistic regression analysis to assess the association between A1AT variants and hepatic events, and calculated Odds ratio (OR) with their 95% confidence intervals (Cl).Results:We included 1532 patients with NAFLD, of which 1249 patients had Pi*MM, 121 had Pi*MS, and 162 had Pi*MZ. Of the 1532 patients, hepatic events developed in 521 (34%) patients. The percentage of patients with Pi*MZ variant was significantly higher in patients with hepatic events as compared to patients without hepatic events (18.7% vs 8.1%, p<0.0001). Pi*MZ variant was noted to significantly increase the odds of developing hepatic events in NAFLD patients, unadjusted OR: 1.82 (1.3-2.5, p<0.001), adjusted OR (for age, sex, body mass index, and diabetes mellitus) 1.76 (1.2-2.5, p=0.002). Pi*MS variant did not increase the odds of hepatic events in NAFLD patients, OR: 0.92 (0.6-1.4, p=0.70).Conclusion:Patients with NAFLD and A1AT Pi*MZ variant are at increased risk for developing hepatic decompensation. NAFLD patients should be offered A1AT genotyping for risk stratification, counseling, and multidisciplinary intervention for NAFLD.