Jon Cardinal

HMGB1: endogenous danger signaling.

While foreign pathogens and their products have long been known to activate the innate immune system, the recent recognition of a group of endogenous molecules that serve a similar function has provided a framework for understanding the overlap between the inflammatory responses activated by pathogens and injury. These endogenous molecules, termed alarmins, are normal cell constituents that can be released into the extracellular milieu during states of cellular stress or damage and subsequently activate the immune system. One nuclear protein, High mobility group box-1 (HMGB1), has received particular attention as fulfilling the functions of an alarmin by being involved in both infectious and non-infectious inflammatory conditions. Once released, HMGB1 signals through various receptors to activate immune cells involved in the immune process. Although initial studies demonstrated HMGB1 as a late mediator of sepsis, recent findings indicate HMGB1 to have an important role in models of non-infectious inflammation, such as autoimmunity, cancer, trauma, and ischemia reperfusion injury. Furthermore, in contrast to its pro-inflammatory functions, there is evidence that HMGB1 also has restorative effects leading to tissue repair and regeneration. The complex functions of HMGB1 as an archetypical alarmin are outlined here to review our current understanding of a molecule that holds the potential for treatment in many important human conditions.

High Mobility Group Box 1 Release from Hepatocytes during Ischemia and Reperfusion Injury Is Mediated by Decreased Histone Deacetylase Activity

The mobilization and extracellular release of nuclear high mobility group box-1 (HMGB1) by ischemic cells activates inflammatory pathways following liver ischemia/reperfusion (I/R) injury. In immune cells such as macrophages, post-translational modification by acetylation appears to be critical for active HMGB1 release. Hyperacetylation shifts its equilibrium from a predominant nuclear location toward cytosolic accumulation and subsequent release. However, mechanisms governing its release by parenchymal cells such as hepatocytes are unknown. In this study, we found that serum HMGB1 released following liver I/R in vivo is acetylated, and that hepatocytes exposed to oxidative stress in vitro also released acetylated HMGB1. Histone deacetylases (HDACs) are a family of enzymes that remove acetyl groups and control the acetylation status of histones and various intracellular proteins. Levels of acetylated HMGB1 increased with a concomitant decrease in total nuclear HDAC activity, suggesting that suppression in HDAC activity contributes to the increase in acetylated HMGB1 release after oxidative stress in hepatocytes. We identified the isoforms HDAC1 and HDAC4 as critical in regulating acetylated HMGB1 release. Activation of HDAC1 was decreased in the nucleus of hepatocytes undergoing oxidative stress. In addition, HDAC1 knockdown with siRNA promoted HMGB1 translocation and release. Furthermore, we demonstrate that HDAC4 is shuttled from the nucleus to cytoplasm in response to oxidative stress, resulting in decreased HDAC activity in the nucleus. Together, these findings suggest that decreased nuclear HDAC1 and HDAC4 activities in hepatocytes following liver I/R is a mechanism that promotes the hyperacetylation and subsequent release of HMGB1.

High‐mobility group box 1 activates caspase‐1 and promotes hepatocellular carcinoma invasiveness and metastases

Hypoxia is often found in solid tumors and is associated with tumor progression and poor clinical outcomes. The exact mechanisms related to hypoxia‐induced invasion and metastasis remain unclear. We elucidated the mechanism by which the nuclear‐damage–associated molecular pattern molecule, high‐mobility group box 1 (HMGB1), released under hypoxic stress, can induce an inflammatory response to promote invasion and metastasis in hepatocellular carcinoma (HCC) cells. Caspase‐1 activation was found to occur in hypoxic HCC cells in a process that was dependent on the extracellular release of HMGB1 and subsequent activation of both Toll‐like receptor 4 (TLR4)‐ and receptor for advanced glycation endproducts (RAGE)‐signaling pathways. Downstream from hypoxia‐induced caspase‐1 activation, cleavage and release of proinflammatory cytokines interleukin (IL)‐1β and ‐18 occurred. We further demonstrate that overexpression of HMGB1 or treatment with recombinant HMGB1 enhanced the invasiveness of HCC cells, whereas stable knockdown of HMGB1 remarkably reduced HCC invasion. Moreover, in a murine model of HCC pulmonary metastasis, stable knockdown of HMGB1 suppressed HCC invasion and metastasis. Conclusion: These results suggest that in hypoxic HCC cells, HMGB1 activates TLR4‐ and RAGE‐signaling pathways to induce caspase‐1 activation with the subsequent production of multiple inflammatory mediators, which, in turn, promote cancer invasion and metastasis. (HEPATOLOGY 2012;55:1866–1875)

Noninvasive radiofrequency ablation of cancer targeted by gold nanoparticles

INTRODUCTION Current radiofrequency ablation (RFA) techniques require invasive needle placement and are limited by accuracy of targeting. The purpose of this study was to test a novel non invasive radiowave machine that uses RF energy to thermally destroy tissue. Gold nanoparticles were designed and produced to facilitate tissue heating by the radiowaves. METHODS A solid state radiowave machine consisting of a power generator and transmitting/receiving couplers which transmit radiowaves at 13.56 MHz was used. Gold nanoparticles were produced by citrate reduction and exposed to the RF field either in solutions testing or after incubation with HepG2 cells. A rat hepatoma model using JM-1 cells and Fisher rats was employed using direct injection of nanoparticles into the tumor to focus the radiowaves for select heating. Temperatures were measured using a fiber-optic thermometer for real-time data. RESULTS Solutions containing gold nanoparticles heated in a time- and power-dependent manner. HepG2 liver cancer cells cultured in the presence of gold nanoparticles achieved adequate heating to cause cell death upon exposure to the RF field with no cytotoxicity attributable to the gold nanoparticles themselves. In vivo rat exposures at 35 W using direct gold nanoparticle injections resulted in significant temperature increases and thermal injury at subcutaneous injection sites as compared to vehicle (water) injected controls. DISCUSSION These data show that non invasive radiowave thermal ablation of cancer cells is feasible when facilitated by gold nanoparticles. Future studies will focus on tumor selective targeting of nanoparticles for in vivo tumor destruction.

Oral hydrogen water prevents chronic allograft nephropathy in rats

Reactive oxygen species (ROS) contribute to the development of interstitial fibrosis and tubular atrophy seen in chronic allograft nephropathy (CAN). As molecular hydrogen gas can act as a scavenger of ROS, we tested the effect of treatment with hydrogen water (HW) in a model of kidney transplantation, in which allografts from Lewis rats were orthotopically transplanted into Brown Norway recipients that had undergone bilateral nephrectomy. Molecular hydrogen was dissolved in water and recipients were given HW from day 0 until day 150. Rats that were treated with regular water (RW) gradually developed proteinuria and their creatinine clearance declined, ultimately leading to graft failure secondary to CAN. In contrast, treatment with HW improved allograft function, slowed the progression of CAN, reduced oxidant injury and inflammatory mediator production, and improved overall survival. Inflammatory signaling pathways, such as mitogen-activated protein kinases, were less activated in renal allografts from HW-treated rats as compared with RW-treated rats. Hence, oral HW is an effective antioxidant and antiinflammatory agent that prevented CAN, improved survival of rat renal allografts, and may be of therapeutic value in the setting of transplantation.

Outcomes of curative treatment for hepatocellular cancer in nonalcoholic steatohepatitis versus hepatitis C and alcoholic liver disease.

Concomitant increasing incidences of hepatocellular carcinoma (HCC) and nonalcoholic steatohepatitis (NASH) suggest that a substantial proportion of HCC arises as a result of hepatocellular injury from NASH. The aim of this study was to determine differences in severity of liver dysfunction at HCC diagnosis and long‐term survival outcomes between patients undergoing curative therapy for HCC in the background of NASH compared to hepatitis C virus (HCV) and/or alcoholic liver disease (ALD). Patient demographics and comorbidities, clinicopathologic data, and long‐term outcomes among patients who underwent liver transplantation, hepatic resection, or radiofrequency ablation for HCC were reviewed. From 2000 to 2010, 303 patients underwent curative treatment of HCC; 52 (17.2%) and 162 (53.5%) patients had NASH and HCV and/or alcoholic liver disease. At HCC diagnosis, NASH patients were older (median age 65 versus 58 years), were more often female (48.1% versus 16.7%), more often had the metabolic syndrome (45.1% versus 14.8%), and had lower model for end‐stage liver disease scores (median 9 versus 10) (all P < 0.05). NASH patients were less likely to have hepatic bridging fibrosis or cirrhosis (73.1% versus 93.8%; P < 0.001). After a median follow‐up of 50 months after curative treatment, the most frequent cause of death was liver failure. Though there were no differences in recurrence‐free survival after curative therapy (median, 60 versus 56 months; P = 0.303), NASH patients had longer overall survival (OS) (median not reached versus 52 months; P = 0.009) independent of other clinicopathologic factors and type of curative treatment. Conclusion: Patients with HCC in the setting of NASH have less severe liver dysfunction at HCC diagnosis and better OS after curative treatment compared to counterparts with HCV and/or alcoholic liver disease. (HEPATOLOGY 2012;55:1811–1821)

mTOR and GSK-3 shape the CD4+ T-cell stimulatory and differentiation capacity of myeloid DCs after exposure to LPS.

Prolonged inhibition of the kinase, mammalian target of rapamycin (mTOR), during myeloid dendritic cell (DC) generation confers resistance to maturation. Recently, however, mTOR inhibition immediately before Toll-like receptor ligation has been found to exert proinflammatory effects on myeloid cells, notably enhanced IL-12p40/p70 production. We show, for the first time, that mouse or human DCs generated under mTOR inhibition exhibit markedly enhanced IL-12p70 production after lipopolysaccharide (LPS) stimulation, despite impaired costimulatory molecule expression and poor T-cell stimulatory ability. Consistent with this finding, we reveal that increased IL-12p40 production occurs predominantly in CD86(lo) immature DCs. High IL-12p40/p70 production by CD86(lo) DC resulted from failed down-regulation of glycogen synthase kinase-3 (GSK-3) activity and could not be ascribed to enhanced Akt function. Despite high IL-12p70 secretion, rapamycin-conditioned, LPS-stimulated DCs remained poor T-cell stimulators, failing to enhance allogeneic Th1 cell responses. We also report that inhibition of GSK-3 impedes the ability of LPS-stimulated DCs to induce forkhead box p3 in CD4(+)CD25(-) T cells, as does the absence of IL-12p40/p70. Thus, GSK-3 activity in DC is regulated via signaling linked to mTOR and modulates their capacity both to produce IL-12p40/p70 and induce forkhead box p3 in CD4(+) T cells under inflammatory conditions.

Wnt/β-Catenin Signaling Regulates Cytokine-Induced Human Inducible Nitric Oxide Synthase Expression by Inhibiting Nuclear Factor-κB Activation in Cancer Cells

The human inducible nitric oxide synthase (hiNOS) gene is regulated by nuclear factor kappaB (NF-kappaB) and has recently been shown to be a target of the Wnt/beta-catenin pathway. In this study, we tested the hypothesis that Wnt/beta-catenin signaling might regulate cytokine- or tumor necrosis factor alpha (TNFalpha)-induced hiNOS expression through interaction with NF-kappaB. A cytokine mixture of TNFalpha + interleukin (IL)-1beta + IFNgamma induced a 2- to 3-fold increase in hiNOS promoter activity in HCT116 and DLD1 colon cells, but produced a 2-fold decrease in SW480 colon cancer cells. A similar differential activity was seen in liver cancer cells (HepG2, Huh7, and Hep3B). Overexpression of beta-catenin produced a dose-dependent decrease in NF-kappaB reporter activity and decreased cytokine mixture-induced hiNOS promoter activity. Gel shift for TNFalpha-induced hiNOS NF-kappaB activation showed decreased p50 binding and decreased NF-kappaB reporter activity in the beta-catenin-mutant HAbeta18 cells. Conversely, enhanced p50 binding and increased NF-kappaB reporter activity were seen in HAbeta85 cells, which lack beta-catenin signaling. Coimmunoprecipitation confirmed that beta-catenin complexed with both p65 and p50 NF-kappaB proteins. NF-kappaB-dependent Traf1 protein expression also inversely correlated with the level of beta-catenin. Furthermore, SW480 cells stably transformed with wild-type adenomatous polyposis coli showed decreased beta-catenin protein and increased TNFalpha-induced p65 NF-kappaB binding as well as iNOS and Traf1 expression. Finally, beta-catenin inversely correlated with iNOS and Fas expression in vivo in hepatocellular carcinoma tumor samples. Our in vitro and in vivo data show that beta-catenin signaling inversely correlates with cytokine-induced hiNOS and other NF-kappaB-dependent gene expression. These findings underscore the complex role of Wnt/beta-catenin, NF-kappaB, and iNOS signaling in the pathophysiology of inflammation-associated carcinogenesis.

Amelioration of rat cardiac cold ischemia/reperfusion injury with inhaled hydrogen or carbon monoxide, or both

BACKGROUND Recent advances in novel medical gases, including hydrogen and carbon monoxide (CO), have demonstrated significant opportunities for therapeutic use. This study was designed to evaluate the effects of inhaled hydrogen or CO, or both, on cold ischemia/reperfusion (I/R) injury of the myocardium. METHODS Syngeneic heterotopic heart transplantation was performed in rats after 6 or 18 hours of cold ischemia in Celsior solution. Survival, morphology, apoptosis and marker gene expression were assessed in the grafts after in vivo inhalation of hydrogen (1% to 3%), CO (50 to 250 ppm), both or neither. Both donors and recipients were treated for 1 hour before and 1 hour after reperfusion. RESULTS After 6-hour cold ischemia, inhalation of hydrogen (>2%) or CO (250 ppm) alone attenuated myocardial injury. Prolonged cold ischemia for 18 hours resulted in severe myocardial injury, and treatment with hydrogen or CO alone failed to demonstrate significant protection. Dual treatment with hydrogen and CO significantly attenuated I/R graft injury, reducing the infarcted area and decreasing in serum troponin I and creatine phosphokinase (CPK). Hydrogen treatment alone significantly reduced malondialdehyde levels and serum high-mobility group box 1 protein levels as compared with air-treated controls. In contrast, CO only marginally prevented lipid peroxidation, but it suppressed I/R-induced mRNA upregulation for several pro-inflammatory mediators and reduced graft apoptosis. CONCLUSIONS Combined therapy with hydrogen and CO demonstrated enhanced therapeutic efficacy via both anti-oxidant and anti-inflammatory mechanisms, and may be a clinically feasible approach for preventing cold I/R injury of the myocardium.

Cisplatin prevents high mobility group box 1 release and is protective in a murine model of hepatic ischemia/reperfusion injury†

The nuclear protein high mobility group box 1 (HMGB1) is an important inflammatory mediator involved in the pathogenesis of liver ischemia/reperfusion (I/R) injury. Strategies aimed at preventing its release from stressed or damaged cells may be beneficial in preventing inflammation after I/R. Cisplatin is a member of the platinating chemotherapeutic agents and can induce DNA lesions that are capable of retaining high mobility group proteins inside the nucleus of cells. In vitro studies in primary cultured rat hepatocytes show that nontoxic concentrations of cisplatin can sequester HMGB1 inside the nucleus of hypoxic cells. Similarly, the in vivo administration of nontoxic doses of cisplatin prevents liver damage associated with a well‐established murine model of hepatic I/R as measured by lower circulating serum aminotransferase levels, lower hepatic inflammatory cytokine levels including tumor necrosis factor α and interleukin‐6, lower inducible NO synthase expression, and fewer I/R‐associated histopathologic changes. The mechanism of action in vivo appears to involve the capacity of cisplatin to prevent the I/R‐induced release of HMGB1 as well as to alter cell survival and stress signaling in the form of autophagy and mitogen‐activated protein kinase activation, respectively. Conclusion: Low, nontoxic doses of cisplatin can sequester HMGB1 inside the nucleus of redox‐stressed hepatocytes in vitro and prevent its release in vivo in a murine model of hepatic I/R. Furthermore, cell survival and stress signaling pathways are altered by low‐dose cisplatin. Therefore, platinating agents may provide a novel approach to mitigating the deleterious effects of I/R‐mediated disease processes. (HEPATOLOGY 2009.)