Myeloperoxidase–Positive Inflammatory Cells Participate in Bile Duct Damage in Primary Biliary Cirrhosis Through Nitric Oxide–Mediated Reactions

Abstract

Previous studies have suggested that increased nitric oxide (NO)-mediated products are found in the livers of subjects with primary biliary cirrhosis (PBC), but the mechanisms involved remain enigmatic. We took advantage of immunohistochemistry and several unique monoclonal antibodies to study inflammatory cells responsible for the generation of NO, the enzymes responsible for NO production, the expression of 3-nitrotyrosine, and the presence of CD68(+) and/or myeloperoxidase (MPO)(+) cells. We examined a total of 113 liver specimens, including 64 with PBC, 19 with primary sclerosing cholangitis (PSC), 6 with non-A, non-B hepatitis, 6 with alcoholic liver disease, 4 with cryptogenic cirrhosis, 4 with biliary atresia, and 10 normal subjects. Twenty-two percent of PBC had elevated expression of 3-nitrotyrosine in their bile duct epithelial cells (BECs) (P =.0316). Furthermore, the BECs in PBC also demonstrated apoptotic changes. MPO-positive inflammatory cells were also noted adjacent to the basement membrane. In contrast, the liver of normal subjects showed few apoptotic changes in the bile ducts, with no evidence of MPO staining in the portal area. Furthermore, sections from livers of subjects with stage I or stage II PBC demonstrated significantly increased inflammatory cell infiltration (P =.0064) and elevated 3-nitrotyrosine expression in BECs (P =.0246) compared with stage III and IV. The presence of 3-nitrotyrosine was closely associated with infiltrating CD68- and/or MPO-positive cells. There was also a stage-associated difference in the presence of bile duct infiltrating cells and 3-nitrotyrosine in PBC with an increase dominant in early stage disease. In conclusion, NO and reactive oxygen species, collectively determined as 3-nitrotyrosine, are associated with bile duct destruction in PBC and are particularly prevalent in early stage disease.

Activation of ATM signaling pathway is involved in oxidative stress-induced expression of mito-inhibitory p21WAF1/Cip1 in chronic non-suppurative destructive cholangitis in primary biliary cirrhosis: An immunohistochemical study

“…The expressions of p21 WAF1/Cip1 and 8-OHdG were evident in the nuclei of hepatocytes in NASH in this study, as previously reported [21], suggesting that oxidative stress is involved not only in hepatocellular damage in NASH but also in biliary epithelial damage of small bile ducts showing CNSDC of PBC. There are several other reports that oxidative stress may be related to the pathogenesis of biliary epithelial damage in CNSDC followed by biliary epithelial apoptosis [11,28,29]. It is difficult to state that the oxidative stress related to p21 WAF1/Cip1 and 8-OHdG expression is a primary pathologic phenomenon of the bile ducts in PBC or a secondary event to inflammatory cell infiltration of PBC livers.…”

“…For example, Tinmouth et al reported that the apoptosis of BECs in PBC is secondary to intense periductal inflammation [9]. In particular, the infiltration of MPO-expressing cells and eosinophils around the bile ducts is thought to be a candidate generator of oxidative stress in PBC [11,28,29]. At present, it seems at least partly possible that the intraepithelial infiltration of MPO-positive cells is rather characteristic of damaged bile ducts in PBC as well as chronic hepatic allograft rejection, and the oxidative stress donors are MPO-positive intraepithelial-infiltrating cells of damaged bile ducts [11,16].…”

“…These findings strongly suggest that activation of the ATM pathway is involved in the induction of p21 WAF1/Cip1 and 8-OHdG by oxidative stress in damaged small bile ducts in PBC. However, to determine whether ATM phosphorylation or participation of the ATM/p53/p21 WAF1/Cip1 pathway is necessary and sufficient for the induction of oxidative stressinduced BEC damage followed by apoptosis or cellular senescence [11,28,29], further studies, such as cell culture or animal studies, are necessary.…”

Increased expression of nuclear envelope gp210 antigen in small bile ducts in primary biliary cirrhosis

“…In addition, the immunostaining score for gp210 antigens was positively correlated to the degree of portal inflammation, interface hepatitis and lobular inflammation. Therefore, we speculate that the increased immunoreactivity of gp210 antigen of BECs in PBC is possibly associated with various conditions including a putative attack by antigen-specific T cells [16e18], an effect of various proinflammatory cytokines [19], a state of increased apoptosis with glutathione depletion [20], increased nuclear DNA fragmentation and Bcl-2 expression [21,22], active lipid peroxidation [23], induction of inducible nitric oxide synthase (iNOS) and reactive oxygen species (ROS) [24,25], and increased expression of p53 and WAF1(p21 cip1/WAF1 ) [26].…”

Cutting Edge Issues in Primary Sclerosing Cholangitis

“…In our previous study of 19 PSC patient liver biopsies, 84% of patients with PSC had inflammatory cells localized to the portal area, although only four (21%) were found to have inflammatory cells infiltrating the small bile ducts. When compared with normal subjects, PSC (P<0.0001) had a significantly higher number of tissue sections with CD68-and/or MPO-positive cells in the portal areas [59].…”