Protein 4.1R (4.1R) is a multifunctional component of the red cell membrane. It forms a ternary complex with actin and spectrin, which defines the nodal junctions of the membrane-skeletal network, and its attachment to the transmembrane protein glycophorin C creates a bridge between the protein network and the membrane bilayer. We now show that deletion of 4.1R in mouse red cells leads to a large diminution of actin accompanied by extensive loss of cytoskeletal lattice structure, with formation of bare areas of membrane. Whereas band 3, the preponderant transmembrane constituent, and proteins known to be associated with it are present in normal or increased amounts, glycophorin C is missing and XK, Duffy, and Rh are much reduced in the 4.1R-deficient cells. The inference that these are associated with 4.1R was borne out by the results of in vitro pulldown assays. Furthermore, whereas Western blot analysis showed normal levels of band 3 and Kell, flow cytometric analysis using an antibody against the extracellular region of band 3 or Kell revealed reduction of these two proteins, suggesting a conformational change of band 3 and Kell epitopes. Taken together, we suggest that 4.1R organizes a macromolecular complex of skeletal and transmembrane proteins at the junctional node and that perturbation of this macromolecular complex not only is responsible for the well characterized membrane instability but may also remodel the red cell surface. macromolecular complex ͉ cytoskeleton

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Fibrosis is the major determinant of morbidity and mortality in patients with nonalcoholic steatohepatitis (NASH) but has no approved pharmacotherapy in part because of incomplete understanding of its pathogenic mechanisms. Here, we report that hepatocyte Notch activity tracks with disease severity and treatment response in patients with NASH and is similarly increased in a mouse model of diet-induced NASH and liver fibrosis. Hepatocyte-specific Notch loss-of-function mouse models showed attenuated NASH-associated liver fibrosis, demonstrating causality to obesity-induced liver pathology. Conversely, forced activation of hepatocyte Notch induced fibrosis in both chow- and NASH diet–fed mice by increasing Sox9-dependent Osteopontin (Opn) expression and secretion from hepatocytes, which activate resident hepatic stellate cells. In a cross-sectional study, we found that OPN explains the positive correlation between liver Notch activity and fibrosis stage in patients. Further, we developed a Notch inhibitor [Nicastrin antisense oligonucleotide (Ncst ASO)] that reduced fibrosis in NASH diet–fed mice. In summary, these studies demonstrate the pathological role and therapeutic accessibility of the maladaptive hepatocyte Notch response in NASH-associated liver fibrosis.

In explant livers with chronic hepatitis C (HCV-C) we have noted a distinctive histologic variant that we have termed steatohepatitic hepatocellular carcinoma (SH-HCC) with features resembling non-neoplastic steatohepatitis, including large droplet steatosis, ballooning of malignant hepatocytes, Mallory-Denk bodies, inflammation, and pericellular fibrosis. This study was undertaken to further describe the characteristics and prevalence of this histologic variant in HCV-C and any possible association with underlying risk factors for nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH). We selected two 2-year periods (mid-2003 to mid-2005 and 2007 to 2008), from which selected explant livers with HCV-C and HCC were examined to determine the characteristics and frequency of SH-HCC. The underlying cirrhotic liver was also reassessed for steatosis and evidence of steatohepatitis. Clinical records were consulted for concomitant NAFLD and NASH risk factors. The SH-HCC variant was found in a total of 22 of 62 HCC cases (35.5%). Fourteen of the 22 patients with SH-HCC (63.6%) had at least one known risk factor for NAFLD/NASH including diabetes (6 of 22, 27.3%), obesity (6 of 22, 27.3%), hypertension (11 of 22, 50%), and hyperlipidemia (5 of 22, 27.8%). In 14 of the 22 cases (63.6%) of SH-HCC, the non-neoplastic liver showed changes of NAFLD/NASH superimposed on otherwise typical features of HCV-C. In conclusion, in our series of HCV-C explants, approximately one-third of HCCs show a distinctive histological variant termed SH-HCC. Underlying risk factors for NAFLD and for NASH were identified in 63.6% of our cases. Moreover, non-neoplastic tissue in HCV-C explants showed changes of NAFLD/NASH in 63.6% of cases. These results suggest a possible NAFLD/NASH pathway leading to SH-HCC in the setting of HCV-C which requires further investigation in the future.

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