Decrease in the prevalence of IL-4-producing CD4+ T cells in patients with advanced stage of primary biliary cirrhosis

Peroxisome Proliferator-Activated Receptors Regulate Hepatic Immunity and Assist in the Treatment of Primary Biliary Cholangitis

Fibrates, which are agonists of peroxisome proliferator-activated receptor alpha, have received increasing attention in the treatment of primary biliary cholangitis. Reduced alkaline phosphatase levels and improved clinical outcomes were observed in patients with primary biliary cholangitis with an inadequate response to ursodeoxycholic acid (UDCA) monotherapy4 when treated with bezafibrate or fenofibrate combined with UDCA. In contrast to obeticholic acid, which exacerbates pruritus in patients, fibrates have been shown to relieve pruritus. Clinical trial outcomes show potential for the treatment of primary biliary cholangitis by targeting peroxisome proliferator-activated receptors. It is currently agreed that primary biliary cholangitis is an autoimmune-mediated cholestatic liver disease, and peroxisome proliferator-activated receptor is a nuclear receptor that regulates the functions of multiple immune cells, thus playing an important role in regulating innate and adaptive immunity. Therefore, this review focuses on the immune disorder of primary biliary cholangitis and summarizes the regulation of hepatic immunity when peroxisome proliferator-activated receptors are targeted for treating primary biliary cholangitis.

The coexistence of Sjögren's syndrome and primary biliary cirrhosis: a comprehensive review

Organ-specific and systemic autoimmune diseases share numerous features and often coexist in the same patient. Autoimmune cholangitis/primary biliary cirrhosis and Sjogren syndrome represent paradigmatic examples of the common grounds of different autoimmunity phenotypes based on similarities in clinical manifestations and immunopathogenesis. In fact, primary biliary cirrhosis and Sjogren's syndrome have both been coined as an autoimmune epithelitis in which apoptosis may be in both cases the key element to explain the organ-specific immune-mediated injury against the biliary and exocrine gland epithelia, respectively. Further, growing evidence supports in both diseases the view that B cells, T cytotoxic cells, and T helper cells are involved in chronic inflammation, likely via the altered expression of pro-inflammatory cytokines. The presence of estrogen receptors on the biliary and exocrine gland epithelia has been advocated as a key to the female predominance encountered in primary biliary cirrhosis and Sjogren's syndrome. Sadly, despite available data, therapeutic approaches remain largely unsatisfactory and recent studies with mechanistic approaches (as in the case of B cell depletion with rituximab) have been of partial benefit only. Future studies should focus on new molecular tools (single-cell transcriptomics, microRNA, epigenetics) to provide unique insights into common mechanisms.

Deletion of interleukin (IL)-12p35 induces liver fibrosis in dominant-negative TGFβ receptor type II mice

Mice with a dominant-negative transforming growth factor β receptor restricted to T cells (dnTGFβRII mice) develop an inflammatory biliary ductular disease that strongly resembles human primary biliary cirrhosis (PBC). Furthermore, deletion of the gene encoding interleukin (IL)-12p40 resulted in a strain (IL-12p40(-/-) dnTGFβRII) with dramatically reduced autoimmune cholangitis. To further investigate the role of the IL-12 cytokine family in dnTGFβRII autoimmune biliary disease, we deleted the gene encoding the IL-12p35 subunit from dnTGFβRII mice, resulting in an IL-12p35(-/-) dnTGFβRII strain which is deficient in two members of the IL-12 family, IL-12 and IL-35. In contrast to IL-12p40(-/-) mice, the IL-12p35(-/-) mice developed liver inflammation and bile duct damage with similar severity but delayed onset as the parental dnTGFβRII mice. The p35(-/-) mice also demonstrated a distinct cytokine profile characterized by a shift from a T-helper 1 (Th1) to a Th17 response. Strikingly, liver fibrosis was frequently observed in IL-12p35(-/-) mice. In conclusion, IL-12p35(-/-) dnTGFβRII mice, histologically and immunologically, reflect key features of PBC, providing a useful generic model to understand the immunopathology of human PBC.

Biliary innate immunity and cholangiopathy

The intrahepatic biliary tree is a conduit of bile which contains pathogen-associated molecular patterns (PAMPs) such as lipopolysaccharide (LPS) originated from intestinal flora. Human biliary epithelial cells (BEC) express toll-like receptors (TLR) and intracellular adaptor molecules and secrete antibiotic peptides and (pro)inflammatory cytokines via the activation of nuclear transcription factors. However, although human bile contains several PAMPs in normal as well as diseased livers, PAMPs physiologically do not elicit an inflammatory response in the biliary tree, suggesting that tolerance against commensal PAMPs including LPS (endotoxin tolerance) is important in maintaining the homeostasis of biliary innate immunity. Negative regulators of intracellular TLR signalings, peroxisome proliferator activating receptor-gamma (PPAR-gamma) and IRAK-M, are associated with the endotoxin tolerance in BEC. In vivo, PPAR-gamma and IRAK-M are ubiquitously expressed in intrahepatic biliary epithelium, while the expression of PPAR-gamma is reduced in damaged bile ducts of primary biliary cirrhosis (PBC). In addition to antibiotic peptides, several cytokines andchemokines are also secreted from BEC as an innate immune response and these humoral components participate in attracting immunocytes and modulating peribiliary cytokine milieu. BEC have receptors for several cytokines and the expression of TLR in BEC is affected by cytokines, suggesting that biliary innate immunity is regulated by an acquired immunity. A T-helper (Th)1-type cytokine, interferon-gamma, downregulates PPAR-gamma and upregulates TLR, and consequently increases the susceptibility of biliary innate immunity. Because periductal cytokine milieu in PBC is Th1-dominant, the increased susceptibility to PAMPs may be associated with the development of cholangiopathy in PBC. Biliary innate immunity is speculated to be associated with the pathogenesis of biliary diseases as well as the defense against biliary microbial infection.

Molecular mechanisms of cholangiopathy in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is histologically characterized by chronic nonsuppurative destructive cholangitis (CNSDC) and the progressive loss of intrahepatic small bile ducts. Cellular immune mechanisms involving T-cell reaction are thought to be significantly involved in the formation of CNSDC and bile duct loss. In inflamed portal tracts of PBC, CD4+ T cells of Th1 type expressing IFN-gamma or CXCR3 are aggregated and more commonly detected around injured bile ducts than Th2-type CD4+ T cells expressing IL-4 or CCR4, indicating that Th1-dominant cellular immunity plays a more-prominent role in recruitment of memory T-cell subsets in PBC and may be responsible for the progressive bile duct damage. Biliary epithelial apoptosis is demonstrated to be a major pathogenic process of bile duct loss in PBC. In CNSDC, several biliary apoptotic cells, an aberrant expression of Fas antigen (proapoptotic molecule) and decreased expression of bcl-2 and mcl-1 (antiapoptotic molecules) are found, although interlobular bile ducts express bcl-2 and mcl-2 but lack Fas. In addition, the upregulation of WAF1 and p53 related to biliary apoptosis is found in biliary epithelial cells of PBC, which may be due to cell senescence in response to genotoxic damage such as oxidative stress. Several steps and mechanisms during induction and progression of cholangitis and biliary apoptosis followed by bile duct loss are now being proposed in PBC, but future analysis of an etiopathogenesis to explain the characteristic histopathogenesis of PBC is required.

Effects of Hochu‐ekki‐to and Ninjin‐youei‐to, Traditional Japanese Medicines, on Porcine Serum‐Induced Liver Fibrosis in Rats

In this study, we estimated the effects of traditional Japanese medicines on liver fibrosis in Wistar rats injected with porcine serum twice a week for 8 weeks. The rats were orally administered Hochu-ekki-to, Ninjin-youei-to (100 and 300 mg/kg/day) or Sho-saiko-to (300 mg/kg/day) 5 days per week. Serum and liver samples were obtained 2 days after the last porcine serum injection. Hochu-ekki-to and Ninjin-youei-to showed significant suppressive effects on the increase in hepatic hydroxyproline, namely total collagen. Further, Ninjin-youei-to significantly suppressed the increases of type IV collagen localized in the basement membrane and prolyl 4-hydroxylase, a collagen synthesis enzyme, in serum or liver. Hochu-ekki-to showed a similar trend. Although Sho-saiko-to did not significantly suppress the increase in hepatic hydroxyproline, it intensely suppressed serum type IV collagen. Further, Hochu-ekki-to, Ninjin-youei-to, and Sho-saiko-to inhibited the production of fibrogenic cytokines, namely TGF-beta1 and IL-13, in the serum and liver. Additionally, we showed that IL-13 levels were positively correlated with hydroxyproline contents in the liver. These results suggest that Ninjin-youei-to as well as Hochu-ekki-to suppress porcine serum-induced liver fibrosis more effectively than Sho-saiko-to. The effects of these three medicines probably depend on the inhibition of fibrogenic cytokine production, resulting in the suppression of collagen synthesis and deposition in the liver, though different mechanisms underlie their anti-fibrogenic effects.

Endogenous interferon gamma protects against cholestatic liver injury in mice

Cholestatic patients suffer from high perioperative morbidity and mortality, but the pathophysiology is still unknown. Interferon gamma (IFN-gamma) may play a role during cholestasis. Therefore, bile duct ligation (BDL) was induced in IFN-gamma alpha-chain receptor-deficient (IFN-gammaR(1)-/-) and wild-type (IFN-gammaR(1)+/+) mice. BDL elicited increased IFN-gamma messenger RNA and protein levels in the liver. One week after BDL, IFN-gammaR(1)+/+ mice showed less severe jaundice and liver injury than IFN-gammaR(1)-/- mice, as reflected by lower bilirubin and liver enzyme levels. In accordance, livers of IFN-gammaR(1)+/+ mice displayed smaller areas of necrosis by two-thirds than IFN-gammaR(1)-/- mice on histopathologic examination (P <.05), whereas mitotic activity and proliferating cell nuclear antigen (PCNA) labeling index was more than twice as high in IFN-gammaR(1)+/+ mice (P <.05). Livers of IFN-gammaR(1)+/+ mice displayed higher rates of apoptosis as indicated by DNA fragmentation rate, the number of apoptotic bodies, and poly ADP-ribose polymerase (PARP) immunostaining. BDL was not associated with lethality in IFN-gammaR(1)+/+ mice; IFN-gammaR(1)-/- mice, however, died from 10 days onward and survival after 2 weeks was 62% (10 of 16). In conclusion, these data suggest that IFN-gamma protects against liver injury during extrahepatic cholestasis by stimulation of apoptosis and subsequent proliferation of hepatocytes, leading to elegant removal of damaged hepatocytes, thus preventing necrosis and concomitant inflammatory responses.

The immunology of primary biliary cirrhosis: the end of the beginning?

The chronic liver disease primary biliary cirrhosis (PBC) is characterised by autoreactive B-cell and T-cell responses directed against mitochondrial antigens. In recent years these responses have been extensively characterised and the principal PBC associated autoantigen identified as pyruvate dehydrogenase complex (PDC). The identification of anti-PDC responses (present in over 95% of PDC patients) has given rise to important questions pertinent to our understanding of the pathogenesis of PBC. What specific role to anti-PDC responses play in target cell damage? How and why does immune tolerance break down to as highly conserved and ubiquitously expressed self-antigen as PDC? Why does breakdown in tolerance to an antigen present in all nucleated cells result in damage restricted to the intra-hepatic bile ducts? In attempting to answer these key questions we have, in this review, proposed a unifying hypothesis for the pathogenesis of PBC.

Tolerance induction across Mls and minor histocompatibility complex by inhibiting activation of T helper type 1 in early period

We have previously succeeded in inducing persistent donor-specific tolerance across Mls plus multiple minor histocompatibility barriers by portal venous (p.v.) injection of donor spleen or bone marrow cells plus cyclophosphamide (CY) treatment. Microchimerism was established in the lymph-hemopoietic organs of the tolerant recipients. However, the mechanisms, particularly the roles of CY in the tolerance induction, have not been clarified. We examined the tolerance induction using other anti-mitotic agents and evaluated the in vitro proliferative responses and cytokine expression of T cells from the recipients after stimulation with donor alloantigens. The administration of not only CY but also mitomycin C (MMC) and cytosin arabinoside (Ara C) elicited a prolongation of skin graft survival. CY induced tolerance when it was administered 2 days after the p.v. injection, but not immediately or 4 days after the p.v. injection. T cells collected from the tolerant recipients showed no proliferative responses as a result of stimulation with donor alloantigens whereas the responses of T cells from non-tolerant recipients were significantly enhanced. Interferon-gamma (IFNgamma) was extensively expressed in the non-tolerant T cells from 24 to 48 h after the stimulation with donor alloantigens. In contrast, the expression of IFNgamma was observed in the tolerant T cells from 72 h after the stimulation. Also, the tolerant T cells showed the expression of interleukin-10 (IL-10) and transforming growth factor-beta 1 (TGF-beta1) from 72 h after the stimulation whereas the non-tolerant T cells did not. These data suggest that CY, when administered 2 days after the p.v. injection, induces persistent tolerance by inhibiting T helper type 1 (Th1) activity in the early period but not the Th1 activity in the later periods.