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Pediatric Transplantation 03/2013; · 1.48 Impact Factor
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ABSTRACT: Dendritic cells (DCs) are critical mediators of immune responses that integrate signals from the innate immune system to orchestrate adaptive host immunity. This study was designed to investigate the role and molecular mechanisms of STAT3-induced β-catenin in the regulation of DC function and inflammatory responses in vitro and in vivo. STAT3 induction in LPS-stimulated mouse bone marrow derived-DCs (BMDCs) triggered β-catenin activation via GSK-3β phosphorylation. The activation of β-catenin inhibited PTEN and promoted PI3K/Akt pathway, which in turn dowregulated DC maturation and function. In contrast, knockdown of β-catenin increased PTEN/TLR4, IRF3, NF-κB activity and proinflammatory cytokine programs in response to LPS stimulation. In a mouse model of warm liver ischemia and reperfusion injury (IRI), disruption of β-catenin signaling increased the hepatocellular damage, enhanced hepatic DC maturation/function and PTEN/TLR4 local inflammation in vivo. Conclusion: Our novel findings underscore the role of β-catenin to modulate DC maturation and function at the innate - adaptive interface. Activation of β-catenin triggered PI3K/Akt which in turn inhibited TLR4-driven inflammatory response in a negative feedback regulatory mechanism. By identifying the molecular pathways by which β-catenin regulates DC function, our findings provide the rationale for novel therapeutic approaches to manage local inflammation and injury in IR-stressed liver. (HEPATOLOGY 2012.).
Hepatology 10/2012; · 11.66 Impact Factor
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ABSTRACT: Hepatic ischemia and reperfusion injury (IRI), an exogenous antigen-independent local inflammation response, occurs in multiple clinical settings including liver transplantation, hepatic resection, trauma, and shock. The immune system and the nervous system maintain extensive communication, and mount a variety of integrated responses to danger signals through intricate chemical messengers. This study examined the function and potential therapeutic potential of neuropeptide PACAP (pituitary adenylate cyclase-activating polypeptide) in a murine model of partial liver "warm" ischemia (90min) followed by reperfusion. Liver IR readily triggered the expression of intrinsic PACAP and its receptors, whereas the hepatocellular damage was exacerbated in PACAP-deficient mice. Conversely, PACAP27, or PACAP38 peptide monotherapy, which elevates intracellular cyclic adenosine monophosphate - protein kinase A (cAMP-PKA) signaling, protected livers from IRI, as evidenced by diminished serum alanine aminotransferase (sALT) levels and well-preserved tissue architecture. The liver protection rendered by PACAP peptides was accompanied by diminished neutrophil/macrophage infiltration and activation, reduced hepatocyte necrosis/apoptosis, and selectively augmented hepatic IL-10 expression. Strikingly, PKA inhibition readily restored liver damage in otherwise IR-resistant PACAP-conditioned mice. In vitro, PACAP treatment not only diminished macrophage TNF-α/IL-6/IL-12 levels in an PKA-dependent manner, but also prevented necrosis and apoptosis in primary mouse hepatocyte cultures. Conclusion: Our novel findings document the importance of PACAP mediated cAMP-PKA signaling in hepatic homeostasis and cytoprotection in vivo. As the enhancement of neural modulation differentially regulates local inflammation and prevents hepatocyte death, these results provide the rationale for novel approaches to manage liver inflammation and IRI in transplant patients. (HEPATOLOGY 2012.).
Hepatology 04/2012; · 11.66 Impact Factor
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ABSTRACT: Hepatic ischemia/reperfusion injury (IRI) occurs in multiple clinical settings, including liver transplantation. The cyclic adenosine monophosphate (cAMP)-dependent protein kinase A (PKA) pathway inhibits hepatocellular apoptosis and regulates toll-like receptor 4-triggered inflammation responses in vitro. Here we examined the function and therapeutic potential of cAMP-PKA activation in a murine (C57/BL6) model of liver warm ischemia (90 minutes) followed by reperfusion. Liver IRI triggered cAMP-PKA activation, whereas the administration of its specific inhibitor, H89, exacerbated hepatocellular damage. Conversely, forskolin therapy, which activates PKA by elevating cAMP levels, protected livers from IRI; this was evidenced by diminished serum alanine aminotransferase levels and well-preserved tissue architecture. Liver protection due to cAMP-PKA stimulation was accompanied by diminished neutrophil and macrophage infiltration/activation, reduced hepatocyte necrosis/apoptosis, and increased cAMP response element-binding protein (CREB) expression and augmented interleukin-10 (IL-10) expression. The neutralization of IL-10 restored liver damage in otherwise ischemia/reperfusion-resistant, forskolin-treated mice. In vitro, cAMP-PKA activation diminished macrophage tumor necrosis factor α, IL-6, and IL-12 in an IL-10-dependent manner and prevented necrosis/apoptosis in primary mouse hepatocyte cultures. Our novel findings in a mouse model of liver IRI document the importance of cAMP-PKA signaling in hepatic homeostasis and cytoprotection in vivo. The activation of cAMP-PKA signaling differentially regulates local inflammation and prevents hepatocyte death, and this provides a rationale for novel therapeutic approaches to combating liver IRI in transplant recipients.
Liver Transplantation 01/2012; 18(6):659-70. · 3.39 Impact Factor
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ABSTRACT: Signal transducer and activator of transcription 3 (STAT3), a key mediator of anti-inflammatory cytokine signaling, is essential for heme oxygenase-1 (HO-1)-induced cytoprotection. The phosphoinositide 3-kinase (PI3K)/phosphatase and tensin homolog delete on chromosome 10 (PTEN) pathways regulate diverse innate immune responses. This study was designed to investigate the role of STAT3 in the regulation of PI3K/PTEN cascade after HO-1 induction in a mouse model of innate immune-dominated liver ischemia/reperfusion injury (IRI).
Partial warm ischemia was produced in the left and middle hepatic lobes of C57BL/6 mice for 90 min, followed by 6h of reperfusion.
Mice subjected to Ad-HO-1 transfer were resistant to liver IRI, and this cytoprotective effect correlated with increased intrahepatic PI3K/Akt and diminished PTEN expression. In contrast, mice undergoing adjunctive Ad-HO-1 treatment and STAT3 knockdown (siRNA) remained susceptible to IR-mediated local inflammatory response and hepatocellular damage. Consistent with decreased cell apoptosis and inhibited TLR4 expression after PI3K/Akt activation, treatment with specific PI3k inhibitor increased local inflammation and recreated liver IRI despite Ad-HO-1 gene transfer. Parallel in vitro studies with bone marrow derived-macrophages have confirmed that HO-1-STAT3 axis-induced PI3K/Akt negatively regulated PTEN expression in TLR4-dependent fashion.
These findings underscore the role of HO-1 induced STAT3 in modulating PI3K/PTEN in liver IRI cascade. Activating PI3K/Akt provides negative feedback mechanism for TLR4-driven inflammation. Identifying molecular pathways of STAT3 modulation in the innate immune system provides the rationale for novel therapeutic approaches for the management of liver inflammation and IRI in transplant patients.
Journal of Hepatology 07/2011; 56(2):359-66. · 9.26 Impact Factor
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ABSTRACT: The sensitized patients can develop an accelerated form of graft rejection mediated by humoral and T-cell-mediated responses, which are resistant to currently used immunosuppression.
In our model of fulminant cardiac allograft rejection in sensitized hosts, groups of wild-type (WT) and B-cell-deficient (BKO) mice (B6) were challenged with skin grafts (B/c). Alloreactive CD8 T effector (Teff) activation and T memory (Tmem) differentiation during a 60-day follow-up period were reduced in the absence of B-cell help. The expression of interleukin (IL)-2Rα, IL-7Rα, and IL-15Rα, which support/program CD8 Teff/Tmem expansion, differentiation, and survival, were selectively decreased in BKO hosts. Unlike in WT, in vivo cytotoxic activity analysis of alloreactive Tmem recall response has revealed decreased donor-type (B/c) but not third-party (C3H) cell lysis in sensitized BKO hosts. However, such impaired allo-Ag specific Tmem recall function was insufficient to markedly prolong cardiac allograft survival in sensitized BKO recipients. Indeed, despite quantitative and statistically significant differences between both animal groups, the biological impact of decreased CD8 Teff/Tmem activation and function in the sensitization phase was marginal. Indeed, cardiac allografts underwent fulminant rejection in sensitized BKO, albeit with somewhat delayed kinetics. Interestingly, unlike in naïve counterparts, the rejection cascade remained CD154 blockade-resistant, evidenced by comparable kinetics, and intra-graft cytokine gene profiles in MR1 monoclonal antibody-treated sensitized WT and BKO hosts.
Although B cells were important for optimal alloreactive CD8 Teff/Tmem function in the sensitization phase, the fulminant rejection of cardiac allografts was B-cell-independent, and CD154 blockade-resistant, as in WT hosts.
Transplantation 03/2011; 91(10):1075-81. · 4.00 Impact Factor
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ABSTRACT: We investigated whether native macrophages overexpressing heme oxygenase 1 (HO-1) could protect rat orthotopic liver transplant (OLT) against cold ischemia/reperfusion injury (IRI). Livers from Sprague-Dawley rats were stored at 4°C in University of Wisconsin solution for 24 hours, and then they were transplanted into syngeneic recipients. Bone marrow-derived macrophages (BMMs) that were transfected ex vivo with heme oxygenase 1 adenovirus (Ad-HO-1), β-galactosidase adenovirus (Ad-β-gal), or HO-1 small interfering RNA (siRNA) were infused directly into the OLT before reperfusion. Controls were OLT conditioned with unmodified or scrambled siRNA-transfected cells. The transfer of Ad-HO-1/BMMs increased the survival of OLT to 100% (versus 40%-50% for controls) and decreased serum alanine aminotransferase levels and histological features of hepatocellular damage. In contrast, an infusion of macrophages transfected with HO-1 siRNA/Ad-β-gal failed to affect IRI. Gene therapy-induced HO-1 suppressed toll-like receptor 4 expression, decreased expression of proinflammatory tumor necrosis factor α, interleukin-1β, monocyte chemoattractant protein 1, and chemokine (C-X-C motif) ligand 10, and attenuated endothelial intercellular cell adhesion molecule 1 expression with resultant diminished OLT leukocyte sequestration. Although Ad-HO-1/BMMs decreased the frequency of apoptotic cells positive for terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling and ameliorated caspase-3 activity, the expression of interleukin-10 and antiapoptotic B cell lymphoma 2/B cell lymphoma extra large increased in well-functioning OLT. Thus, the transfer of native macrophages transfected ex vivo with HO-1 can rescue rat iso-OLT from IRI. Our study validates a novel and clinically attractive concept: native macrophages transfected ex vivo with the antioxidant HO-1 can be applied at the time of transplantation to mitigate otherwise damaging antigen-independent liver inflammation and injury resulting from the peritransplant harvesting insult. If this new, refined strategy is proven to be effective in allo-OLT recipients, it should be considered in clinical settings to increase the supply of usable donor organs and ultimately improve the overall success of liver transplantation.
Liver Transplantation 02/2011; 17(2):201-10. · 3.39 Impact Factor
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ABSTRACT: Programmed death-1 (PD-1)/B7-H1 costimulation acts as a negative regulator of host alloimmune responses. Although CD4 T cells mediate innate immunity-dominated ischemia and reperfusion injury (IRI) in the liver, the underlying mechanisms remain to be elucidated. This study focused on the role of PD-1/B7-H1 negative signaling in liver IRI. We used an established mouse model of partial liver warm ischemia (90 minutes) followed by reperfusion (6 hours). Although disruption of PD-1 signaling after anti-B7-H1 monoclonal antibody treatment augmented hepatocellular damage, its stimulation following B7-H1 immunoglobulin (B7-H1Ig) fusion protected livers from IRI, as evidenced by low serum alanine aminotransferase levels and well-preserved liver architecture. The therapeutic potential of B7-H1 engagement was evident by diminished intrahepatic T lymphocyte, neutrophil, and macrophage infiltration/activation; reduced cell necrosis/apoptosis but enhanced anti-necrotic/apoptotic Bcl-2/Bcl-xl; and decreased proinflammatory chemokine/cytokine gene expression in parallel with selectively increased interleukin (IL)-10. Neutralization of IL-10 re-created liver IRI and rendered B7-H1Ig-treated hosts susceptible to IRI. These findings were confirmed in T cell-macrophage in vitro coculture in which B7-H1Ig diminished tumor necrosis factor-α/IL-6 levels in an IL-10-dependent manner. Our novel findings document the essential role of the PD-1/B7-H1 pathway in liver IRI. CONCLUSION: This study is the first to demonstrate that stimulating PD-1 signals ameliorated liver IRI by inhibiting T cell activation and Kupffer cell/macrophage function. Harnessing mechanisms of negative costimulation by PD-1 upon T cell-Kupffer cell cross-talk may be instrumental in the maintenance of hepatic homeostasis by minimizing organ damage and promoting IL-10-dependent cytoprotection.
Hepatology 10/2010; 52(4):1380-9. · 11.66 Impact Factor
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Yoichiro Uchida,
Bibo Ke,
Maria Cecilia S Freitas, Haofeng Ji,
Danyun Zhao,
Elizabeth R Benjamin,
Nader Najafian,
Hideo Yagita,
Hisaya Akiba,
Ronald W Busuttil,
Jerzy W Kupiec-Weglinski
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ABSTRACT: The T cell immunoglobulin and mucin domain-containing molecules (TIM) protein family, which is expressed by T cells, plays a crucial role in regulating host adaptive immunity and tolerance. However, its role in local inflammation, such as innate immunity-dominated organ ischemia-reperfusion injury (IRI), remains unknown. Liver IRI occurs frequently after major hepatic resection or liver transplantation. Using an antagonistic anti-TIM-1 antibody (Ab), we studied the role of TIM-1 signaling in the model of partial warm liver ischemia followed by reperfusion. Anti-TIM-1 Ab monotherapy ameliorated the hepatocellular damage and improved liver function due to IR, as compared with controls. Histological examination has revealed that anti-TIM-1 Ab treatment decreased local neutrophil infiltration, inhibited sequestration of T lymphocytes, macrophages, TIM-1 ligand-expressing TIM-4(+) cells, and reduced liver cell apoptosis. Intrahepatic neutrophil activity and induction of proinflammatory cytokines/chemokines were also reduced in the treatment group. In parallel in vitro studies, anti-TIM-1 Ab suppressed interferon-gamma (IFN-gamma) production in concanavalin A (conA)-stimulated spleen T cells, and diminished tumor necrosis factor alpha (TNF-alpha)/interleukin (IL)-6 expression in a macrophage/spleen T cell coculture system. This is the first study to provide evidence for the novel role of TIM-1 signaling in the mechanism of liver IRI. TIM-1 regulates not only T for the role of cell activation but may also affect macrophage function in the local inflammation response. These results provide compelling data for further investigation of TIM-1 pathway in the mechanism of IRI, to improve liver function, expand the organ donor pool, and improve the overall success of liver transplantation.
Hepatology 04/2010; 51(4):1363-72. · 11.66 Impact Factor
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ABSTRACT: Macrophages play a critical role in the pathophysiology of liver ischemia and reperfusion (IR) injury (IRI). However, macrophages that overexpress antioxidant heme oxygenase-1 (HO-1) may exert profound anti-inflammatory functions. This study explores the cytoprotective effects and mechanisms of ex vivo modified HO-1-expressing bone marrow-derived macrophages (BMDMs) in well-defined mouse model of liver warm ischemia followed by reperfusion. Adoptive transfer of Ad-HO-1-transduced macrophages prevented IR-induced hepatocellular damage, as evidenced by depressed serum glutamic-oxaloacetic transaminase (sGOT) levels and preserved liver histology (Suzuki scores), compared to Ad-beta-gal controls. This beneficial effect was reversed following concomitant treatment with HO-1 siRNA. Ad-HO-1-transfected macrophages significantly decreased local neutrophil accumulation, TNF-alpha/IL-1beta, IFN-gamma/E-selectin, and IP-10/MCP-1 expression, caspase-3 activity, and the frequency of apoptotic cells, as compared with controls. Unlike in controls, Ad-HO-1-transfected macrophages markedly increased hepatic expression of antiapoptotic Bcl-2/Bcl-xl and depressed caspase-3 activity. These results establish the precedent for a novel investigative tool and provide the rationale for a clinically attractive new strategy in which native macrophages can be transfected ex vivo with cytoprotective HO-1 and then infused, if needed, to prospective recipients exposed to hepatic IR-mediated local inflammation, such as during liver transplantation, resection, or trauma.
Molecular Therapy 12/2009; 18(5):1019-25. · 6.87 Impact Factor
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ABSTRACT: We have shown that overexpression of heme oxygenase-1 (HO-1) prevents the liver inflammation response leading to ischemia and reperfusion injury (IRI). This study was designed to explore the precise function and mechanism of HO-1 cytoprotection in liver IRI by employing a small interfering RNA (siRNA) that effectively suppresses HO-1 expression both in vitro and in vivo. Using a partial lobar liver warm ischemia model, mice were injected with HO-1 siRNA/nonspecific control siRNA or Ad-HO-1/Ad-beta-gal. Those treated with HO-1 siRNA showed increased serum glutamic-oxaloacetic transaminase levels, significant liver edema, sinusoidal congestion/cytoplasmic vacuolization, and severe hepatocellular necrosis. In contrast, Ad-HO-1-pretreated animals revealed only minimal sinusoidal congestion without edema/vacuolization or necrosis. Administration of HO-1 siRNA significantly increased local neutrophil accumulation and the frequency of apoptotic cells. Mice treated with HO-1 siRNA were characterized by increased caspase-3 activity and reduced HO-1 expression, whereas those given Ad-HO-1 showed decreased caspase-3 activity and increased HO-1/Bcl-2/Bcl-x(L), data confirmed by use of an in vitro cell culture system. Thus, by using an siRNA approach this study confirms that HO-1 provides potent cytoprotection against hepatic IRI and regulates liver apoptosis. Indeed, siRNA provides a powerful tool with which to study gene function in a wide range of liver diseases.
Human gene therapy 07/2009; 20(10):1133-42. · 4.20 Impact Factor
