Interleukin-1 beta induces the expression of hsp70, heme oxygenase and Mn-SOD in FACS-purified rat islet beta-cells, but not in alpha-cells

New insights into the role and therapeutic potential of HSP70 in diabetes

Emerging evidence indicates that HSP70 represents a key mechanism in the pathophysiology of β-cell dysfunction, insulin resistance, and various diabetic complications, including micro- and macro-vascular alterations, as well as impaired hemostasis. Hyperglycemia, a hallmark of both types of diabetes, increases the circulating levels of HSP70 (eHSP70), but there is still divergence about whether diabetes up- or down-regulates the intracellular fraction of this protein (iHSP70). Here, we consider that iHSP70 levels reduce in diabetic arterial structures and that the vascular system is in direct contact with all other systems in the body suggesting that a systemic response might also be happening for iHSP70, which is characterized by decreased levels of HSP70 in the vasculature. Furthermore, although many pathways have been proposed to explain HSP70's functions in diabetes, and organs/tissues/cells-specific variations occur, the membrane-bound receptor of the innate immune system, Toll-like receptor 4, and its downstream signal transduction pathways appear to be a constant, not only when we explore the actions of eHSP70, but also when we assess the contributions of iHSP70. In this review, we focus on discussing the multiple roles of HSP70 across organs/tissues/cells affected by hyperglycemia to further explore the possibility of targeting this protein with pharmacological and non-pharmacological approaches in the context of diabetes.

Single-cell RNA sequencing of mouse islets exposed to proinflammatory cytokines

Exposure to proinflammatory cytokines is believed to contribute to pancreatic β-cell damage during diabetes development. Although some cytokine-mediated changes in islet gene expression are known, the heterogeneity of the response is not well-understood. After 6-h treatment with IL-1β and IFN-γ alone or together, mouse islets were subjected to single-cell RNA sequencing. Treatment with both cytokines together led to expression of inducible nitric oxide synthase mRNA (Nos2) and antiviral and immune-associated genes in a subset of β-cells. Interestingly, IL-1β alone activated antiviral genes. Subsets of δ- and α-cells expressed Nos2 and exhibited similar gene expression changes as β-cells, including increased expression of antiviral genes and repression of identity genes. Finally, cytokine responsiveness was inversely correlated with expression of genes encoding heat shock proteins. Our findings show that all islet endocrine cell types respond to cytokines, IL-1β induces the expression of protective genes, and cellular stress gene expression is associated with inhibition of cytokine signaling.

MicroRNAs and histone deacetylase inhibition-mediated protection against inflammatory β-cell damage

Inflammatory β-cell failure contributes to type 1 and type 2 diabetes pathogenesis. Pro-inflammatory cytokines cause β-cell dysfunction and apoptosis, and lysine deacetylase inhibitors (KDACi) prevent β-cell failure in vitro and in vivo, in part by reducing NF-κB transcriptional activity. We investigated the hypothesis that the protective effect of KDACi involves transcriptional regulation of microRNAs (miRs), potential new targets in diabetes treatment. Insulin-producing INS1 cells were cultured with or without the broad-spectrum KDACi Givinostat, prior to exposure to the pro-inflammatory cytokines IL-1β and IFN-γ for 6 h or 24 h, and miR expression was profiled with miR array. Thirteen miRs (miR-7a-2-3p, miR-29c-3p, miR-96-5p, miR-101a-3p, miR-140-5p, miR-146a-5p, miR-146b-5p, miR-340-5p, miR-384-5p, miR-455-5p, miR-466b-2-3p, miR-652-5p, and miR-3584-5p) were regulated by both cytokines and Givinostat, and nine were examined by qRT-PCR. miR-146a-5p was strongly regulated by cytokines and KDACi and was analyzed further. miR-146a-5p expression was induced by cytokines in rat and human islets. Cytokine-induced miR-146a-5p expression was specific for INS1 and β-TC3 cells, whereas α-TC1 cells exhibited a higher basal expression. Transfection of INS1 cells with miR-146a-5p reduced cytokine signaling, including the activity of NF-κB and iNOS promoters, as well as NO production and protein levels of iNOS and its own direct targets TNF receptor associated factor 6 (TRAF6) and interleukin-1 receptor-associated kinase 1 (IRAK1). miR-146a-5p was elevated in the pancreas of diabetes-prone BB-DP rats at diabetes onset, suggesting that miR-146a-5p could play a role in type 1 diabetes development. The miR array of cytokine-exposed INS1 cells rescued by KDACi revealed several other miRs potentially involved in cytokine-induced β-cell apoptosis, demonstrating the strength of this approach.

A novel role for carbon monoxide as a potent regulator of intracellular Ca2+and nitric oxide in rat pancreatic acinar cells

Carbon monoxide (CO) is known as an essential gaseous messenger that regulates a wide array of physiological and pathological processes, similar to nitric oxide (NO) and hydrogen sulfide. The aim of the present study was to elucidate the potential role of CO in Ca2+homeostasis and to explore the underlying mechanisms in pancreatic acinar cells. The exogenous application of a CO-releasing molecule dose-dependently increased intracellular Ca2+concentration ([Ca2+]i). A heme oxygenase (HO) inducer increased [Ca2+]iin a concentration-dependent manner, and the increase was diminished by an HO inhibitor. The CO-induced [Ca2+]iincrease persisted in the absence of extracellular Ca2+, indicating that Ca2+release is the initial source for the increase. The inhibition of G protein, phospholipase C (PLC), and inositol 1,4,5-trisphosphate (IP3) receptor diminished the CO-induced [Ca2+]iincrease. CO upregulated endothelial nitric oxide synthase (eNOS) expression and stimulated NO production, and NOS inhibitor, calmodulin inhibitor, or the absence of extracellular Ca2+eliminated the latter response. Blocking the phosphatidylinositol 3-kinase (PI3K)-Akt/protein kinase B (PKB) pathway abolished CO-induced NO production. Pretreatment with an NOS inhibitor, NO scavenger, or soluble guanylate cyclase inhibitor, did not affect the CO-induced [Ca2+]iincrease, indicating that NO, soluble guanylate cyclase, and cyclic guanosine 5′-monophosphate are not involved in the CO-induced [Ca2+]iincrease. CO inhibited the secretory responses to CCK-octapeptide or carbachol. We conclude that CO acts as a regulator not only for [Ca2+]ihomeostasis via a PLC-IP3-IP3receptor cascade but also for NO production via the calmodulin and PI3K-Akt/PKB pathway, and both CO and NO interact. Moreover, CO may provide potential therapy to ameliorate acute pancreatitis by inhibiting amylase secretion.

Toll-like receptors and NLRP3 as central regulators of pancreatic islet inflammation in type 2 diabetes

The global health and economic burden of type 2 diabetes (T2D) has reached staggering proportions. Current projections estimate that 592 million people will have diabetes by 2035. T2D-which comprises 90% of cases-is a complex disease, in most cases resulting from a combination of predisposing genes and an unhealthy environment. Clinical onset of the disease occurs when pancreatic β cells fail in the face of insulin resistance. It has long been appreciated that chronic activation of the innate immune system is associated with T2D, and many organs critical to the regulation of glucose homeostasis show signs of a chronic inflammatory process, including the pancreatic islets of Langerhans. Recent clinical trials using IL-1-targeting agents have confirmed that inflammation contributes to β-cell failure in humans with T2D. However, little is known about the nature of the pro-inflammatory response within the islet, and there is considerable debate about the triggers for islet inflammation, which may be systemically derived and/or tissue-specific. In this review, we present evidence that Toll-like receptors 2 and 4 and the NLRP3 (Nucleotide-binding oligomerization domain, Leucine-rich Repeat and Pyrin domain containing 3) inflammasome are triggers for islet inflammation in T2D and propose that the activation of macrophages by these triggers mediates islet endocrine cell dysfunction. Therapeutically targeting these receptors may improve hyperglycemia and protect the β cell in T2D.

Do post-translational beta cell protein modifications trigger type 1 diabetes?

Type 1 diabetes is considered an autoimmune disease characterised by specific T cell-mediated destruction of the insulin-producing beta cells. Yet, except for insulin, no beta cell-specific antigens have been discovered. This may imply that the autoantigens in type 1 diabetes exist in modified forms capable of specifically triggering beta cell destruction. In other immune-mediated diseases, autoantigens targeted by the immune system have undergone post-translational modification (PTM), thereby creating tissue-specific neo-epitopes. In a similar manner, PTM of beta cell proteins might create beta cell-specific neo-epitopes. We suggest that the current paradigm of type 1 diabetes as a classical autoimmune disease should be reconsidered since the immune response may not be directed against native beta cell proteins. A modified model for the pathogenetic events taking place in islets leading to the T cell attack against beta cells is presented. In this model, PTM plays a prominent role in triggering beta cell destruction. We discuss literature of relevance and perform genetic and human islet gene expression analyses. Both direct and circumstantial support for the involvement of PTM in type 1 diabetes exists in the published literature. Furthermore, we report that cytokines change the expression levels of several genes encoding proteins involved in PTM processes in human islets, and that there are type 1 diabetes-associated polymorphisms in a number of these. In conclusion, data from the literature and presented experimental data support the notion that PTM of beta cell proteins may be involved in triggering beta cell destruction in type 1 diabetes. If the beta cell antigens recognised by the immune system foremost come from modified proteins rather than native ones, the concept of type 1 diabetes as a classical autoimmune disease is open for debate.

Development of diabetes in lean Ncb5or-null mice is associated with manifestations of endoplasmic reticulum and oxidative stress in beta cells

NADH-cytochrome b5 oxidoreductase (Ncb5or) is an endoplasmic reticulum (ER)-associated redox enzyme involved in fatty acid metabolism, and phenotypic abnormalities of Ncb5or(-/-) mice include diabetes and lipoatrophy. These mice are lean and insulin-sensitive but become hyperglycemic at age 7 weeks as a result of β-cell dysfunction and loss. Here we examine early cellular and molecular events associated with manifestations of β-cell defects in Ncb5or(-/-) mice. We observe lower islet β-cell content in pancreata at age 4 weeks and prominent ER distention in β-cells by age 5 weeks. Ultrastructural changes progress rapidly in severity from age 5 to 6 weeks, and their frequency rises from 10% of β-cells at 5 weeks to 33% at 6 weeks. These changes correlate temporally with the onset of diabetes. ER stress responses and lipid load in Ncb5or(-/-) β-cells were assessed with isolated islets from mice at age 5 weeks. Expression levels of the stress marker protein Grp78/BiP and of phosphorylated eIF2α protein were found to be reduced, although their transcript levels did not decline. This pattern stands in contrast to the canonical unfolded protein response. Ncb5or(-/-) β-cells also accumulated higher intracellular levels of palmitate and other free fatty acids and exhibited greater reactive oxygen species production than wild-type cells. An alloxan-susceptible genetic background was found to confer accelerated onset of diabetes in Ncb5or(-/-) mice. These findings provide the first direct evidence that manifestations of diabetes in lean Ncb5or(-/-) mice involve saturated free fatty acid overload of β-cells and ER and oxidative stress responses.

Overexpression of the nuclear factor-κB subunit c-Rel protects against human islet cell death in vitro

The transcription factor nuclear factor (NF)-κB is known to modulate rates of apoptosis and may therefore play a role in the increased β-cell death that occurs in type 1 and type 2 diabetes. The aim of the present investigation was to study the expression of NF-κB subunits in human islet cells and whether overexpression of the NF-κB subunit c-Rel affects islet cell survival. We detected expression of p65, Rel-B, p50, p105, p52, and the ribosomal protein S3 (rpS3) in human islet cells. Among these, only p65 and rpS3 were translocated from the cytosolic to the nuclear fraction in response to cytokines. Interestingly, rpS3 participated in p65 binding to the κB-element in gel shift analysis experiments. We observed cytoplasmic c-Rel expression in vivo in 6J mice, and signs of nuclear translocation in β-cells of infiltrated nonobese diabetic islets. Human islet cells were also dispersed by trypsin treatment and transduced with a c-Rel adenoviral vector. This resulted in increased expression of c-Rel and inhibitory factor κB, increased κB-binding activity, and augmented protein levels of Bcl-X(L,) c-IAP2, and heat shock protein 72. c-Rel expression in human islet cells protected against cytokine-induced caspase 3 activation and cell death. c-Rel protected also against streptozotocin- and H(2)O(2)-induced cell death, in both intact rat islets and human islet cells. We conclude that rpS3 participates in NF-κB signaling and that a genetic increase in the activity of the NF-κB subunit c-Rel results in protection against cell death in human islets.

Overexpression of SIRT1 protects pancreatic beta-cells against cytokine toxicity by suppressing the nuclear factor-kappaB signaling pathway

OBJECTIVE

SIRT1, a class III histone/protein deacetylase, is known to interfere with the nuclear factor-kappaB (NF-kappaB) signaling pathway and thereby has an anti-inflammatory function. Because of the central role of NF-kappaB in cytokine-mediated pancreatic beta-cell damage, we postulated that SIRT1 might work in pancreatic beta-cell damage models.

RESEARCH DESIGN AND METHODS

RINm5F (RIN) cells or isolated rat islets were treated with interleukin-1beta and interferon-gamma. SIRT1 was activated by resveratrol, a pharmacological activator, or ectopic overexpression. The underlying mechanisms of SIRT1 against cytokine toxicity were further explored.

RESULTS

Treatment of RIN cells with cytokines induced cell damage, and this damage was well correlated with the expression of the inducible form of nitric oxide (NO) synthase (iNOS) and NO production. However, SIRT1 overexpression completely prevented cytokine-mediated cytotoxicity, NO production, and iNOS expression. The molecular mechanism by which SIRT1 inhibits iNOS expression appeared to involve the inhibition of the NF-kappaB signaling pathway through deacetylation of p65. In addition, SIRT1 activation by either resveratrol or adenoviral-directed overexpression of SIRT1 could prevent cytokine toxicity and maintain normal insulin-secreting responses to glucose in isolated rat islets.

CONCLUSIONS

This study will provide valuable information not only into the mechanisms underlying beta-cell destruction but also into the regulation of SIRT1 as a possible target to attenuate cytokine-induced beta-cell damage.

Guggulsterone, a plant sterol, inhibits NF-kappaB activation and protects pancreatic beta cells from cytokine toxicity

Guggulsterone has been used to treat hyperlipidemia, arthritis, and obesity. Although its anti-inflammatory and anti-hyperlipidemic effects have been well documented, the effect of guggulsterone on pancreatic beta cells is unknown. Therefore, in this study, the effect of guggulsterone on IL-1beta- and IFN-gamma-induced beta-cell damage was investigated. Treatment of RINm5F (RIN) rat insulinoma cells with IL-1beta and IFN-gamma induced cell damage, and this damage was well correlated with nitric oxide (NO) and prostaglandin E2 (PGE2) production. However, guggulsterone completely prevented cytokines-mediated cytotoxicity, as well as NO and PGE2 production, and these effects were correlated with reduced levels of the inducible form of NO synthase (iNOS) and cyclooxygenase-2 (COX-2) mRNA and protein expressions. The molecular mechanism by which guggulsterone inhibits iNOS and COX-2 gene expressions appeared to involve the inhibition of NF-kappaB activation. The cytoprotective effects of guggulsterone were also mediated through the suppression of the JAK/STAT pathway. Cells treated with the cytokines downregulated the protein level of SOCS-3, however pretreatment with guggulsterone attenuated this decrease. Additionally, in a second set of experiments in which rat islets were used, the findings regarding the beta-cell protective effects of guggulsterone were essentially the same as those observed when RIN cells were used; guggulsterone prevented cytokines-induced NO and PGE2 production, iNOS and COX-2 expressions, JAK/STAT activation, NF-kappaB activation, downregulation of SOCS-3, and impairment of glucose-stimulated insulin secretion. Collectively, these results suggest that guggulsterone may be used to preserve functional beta-cell mass.

Gene expression profiling in practitioners of Sudarshan Kriya

BACKGROUND

The rapid pace of life, eating habits, and environmental pollution have increased stress levels and its related disorders. The complex molecular response to stress is mediated by stress genes and a variety of regulatory pathways. Oxidative stress is internal damage caused by reactive oxygen species. Increasing evidence suggests that chronic psychosocial stress may increase oxidative stress, which in turn may contribute to aging, and etiology of coronary diseases, cancer, arthritis, etc. Psychophysiological concomitants of meditation have been extensively researched, but there are very little data available on biochemical activity leading to relieving stress by causing a relaxation response by Sudarshan Kriya (SK). SK is a breathing technique that involves breathing in three different rhythms. It is preceded by Ujjayi Pranayam (long and deep breaths with constriction at the base of throat) and Bhastrika (fast and forceful breaths through nose along with arm movements).

METHODS

Forty-two SK practitioners and 42 normal healthy controls were recruited for our study. The practitioners had practiced SK for at least 1 year. Selected normal healthy controls did not perform any conventional physical exercise or any formal stress management technique. Whole blood was used for glutathione peroxidase estimation and red blood cell lysate was used for superoxide dismutase activity assay and for glutathione estimation. White blood cells were isolated from fresh blood and assayed for gene expression using reverse transcriptase-polymerase chain reaction. The parameters studied are antioxidant enzymes, genes involved in oxidative stress, DNA damage, cell cycle control, aging, and apoptosis.

RESULTS

A better antioxidant status both at the enzyme activity and RNA level was seen in SK practitioners. This was accompanied by better stress regulation and better immune status due to prolonged life span of lymphocytes by up-regulation of antiapoptotic genes and prosurvival genes in these subjects.

CONCLUSIONS

Our pilot study provides the first evidence suggesting that SK practice may exert effects on immunity, aging, cell death, and stress regulation through transcriptional regulation.

Genistein protects pancreatic beta cells against cytokine-mediated toxicity

In the past few decades, the use of genistein as an anti-inflammatory agent has gained much attention. Our current study focuses on the preventive effects of genistein on cytokine-induced pancreatic beta-cell damage. Treatment of RINm5F (RIN) rat insulinoma cells with interleukin (IL)-1beta and interferon (IFN)-gamma induced cell damage, which was correlated with nitric oxide (NO) production. Genistein completely prevented cytokine-mediated cytotoxicity and NO production, a finding that correlated well with reduced levels of the inducible form of NO synthase (iNOS) mRNA and protein. The molecular mechanism of genistein inhibition of iNOS gene expression appeared to involve the inhibition of NFkappaB activation. The cytokine induced increases in NFkappaB binding activity, nuclear p50 and p65 subunit levels, and IkappaBalpha degradation in cytosol compared to unstimulated cells; genistein abolished all of these parameters. The cytoprotective effects of genistein are also mediated through the suppression of ERK-1/2 and Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathways. In a second set of experiments, rat islets were used. The findings on beta-cell protective effects of genistein were essentially the same as for the RIN cell data, namely genistein prevented cytokine-induced NO production, iNOS expression, ERK-1/2 activation, JAK/STAT activation, and impairment of glucose-stimulated insulin secretion. Collectively, these results suggest that genistein might be used to preserve functional beta-cell mass.

Activation of peroxisome proliferator-activated receptor-γ protects pancreatic β-cells from cytokine-induced cytotoxicity via NFκB pathway

Diabetes mellitus is characterized by cytokine-induced insulitis and a deficit in beta-cell mass. Ligands for peroxisome proliferator-activated receptor-gamma (PPAR-gamma) have been shown to have anti-inflammatory effects in various experimental models. We questioned whether activation of endogenous PPAR-gamma by either PPAR-gamma ligands or adenoviral-directed overexpression of PPAR-gamma (Ad-PPAR-gamma) could inhibit cytokine-induced beta-cell death in RINm5F (RIN) cells, a rat insulinoma cell line. Treatment of RIN cells with interleukin-1 beta (IL-1 beta) and interferon-gamma (IFN-gamma) induced beta-cell damage through NF kappaB-dependent signaling pathways. Activation of PPAR-gamma by PPAR-gamma ligands or Ad-PPAR-gamma inhibited IL-1 beta and IFN-gamma-stimulated nuclear translocation of the p65 subunit and DNA binding activity. NF kappaB target gene expression and their product formation, namely inducible nitric oxide synthase and cyclooxygenase-2 were decreased by PPAR-gamma activation, as established by real-time PCR, Western blots and measurements of NO and PGE(2). The mechanism by which PPAR-gamma activation inhibited NF kappaB-dependent cell death signals appeared to involve the inhibition of I kappa B alpha degradation, evidenced by inhibition of cytokine-induced NF kappaB-dependent signaling events by Ad-I kappaB alpha (S32A, S36A), non-degradable I kappaB alpha mutant. I kappaB beta mutant, Ad-I kappaB beta (S19A, S23A) was not effective in preventing cytokine toxicity. Furthermore, a protective effect of PPAR-gamma ligands was proved by assaying for normal insulin secreting capacity in response to glucose in isolated rat pancreatic islets. The beta-cell protective function of PPAR-gamma ligands might serve to counteract cytokine-induced beta-cell destruction.

Variations in IB1/JIP1 expression regulate susceptibility of beta-cells to cytokine-induced apoptosis irrespective of C-Jun NH2-terminal kinase signaling

We previously reported that interleukin-1beta (IL-1beta) alone does not cause apoptosis of beta-cells, whereas when combined with gamma-interferon (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha), it exerts a distinct apoptotic effect. Studies in beta-cell lines indicated that IL-1beta reduced expression of islet brain (IB)-1/JNK interacting protein (JIP)-1, a JNK scaffold protein with antiapoptotic action. We examined whether variations in IB1/JIP-1 expression in purified primary beta-cells affect their susceptibility to cytokine-induced apoptosis. Exposure to IL-1beta for 24 h decreased cellular IB1/JIP-1 content by 66 +/- 17%; this IL-1beta effect was maintained in the presence of TNF-alpha + IFN-gamma, which did not influence IB1/JIP-1 levels by themselves. Addition of IL-1beta to TNF-alpha + IFN-gamma increased apoptosis from 20 +/- 2% to 59 +/- 5%. A similar increase in TNF-alpha + IFN-gamma-induced apoptosis was produced by adenoviral expression of antisense IB1/JIP-1 and was not further enhanced by addition of IL-1beta, indicating that IL-1beta-mediated suppression of IB1/JIP-1 in beta-cells increases their susceptibility to cytokine-induced apoptosis. However, adenovirally mediated overexpression of IB1/JIP-1 also potentiated TNF-alpha + IFN-gamma-induced apoptosis, suggesting that the antiapoptotic effect of IB1/JIP-1 depends on well-defined cellular levels. We conclude that the IB1/JIP-1 level in beta-cells can control their susceptibility to apoptosis independent of JNK signaling.

Haeme-oxygenase 1 expression in rat pancreatic beta cells is stimulated by supraphysiological glucose concentrations and by cyclic AMP

AIM/HYPOTHESIS

Increased expression of haeme-oxygenase 1 (HO1) and other antioxidant enzymes could improve pancreatic beta-cell survival under stressful conditions, including hyperglycaemia. However, how hyperglycaemia increases islet HO1 expression is not known.

METHODS

Rat islets were pre-cultured for 1 week in RPMI medium containing 10 mmol x l(-1) glucose (G10), and further cultured overnight in G5-G30 plus various test substances. Islet HO1 mRNA and protein expression was measured by semiquantitative RT-PCR, western blot, and immunohistochemistry.

RESULTS

Islet HO1 mRNA expression was minimal after overnight culture in G10, slightly increased in G5, and increased by five- to ten-fold in G30 in parallel with a heterogeneous increase in beta-cell HO1 protein expression. The effect of G30 was fully inhibited by agents decreasing cytosolic Ca2+ (diazoxide, nimodipine), but was only slightly reproduced by agents raising Ca2+ (tolbutamide, 30 mmol x l(-1) potassium). It was also suppressed by the alpha2-adrenoceptor agonist clonidine, whereas dibutyryl-cyclic-AMP largely increased beta-cell HO1 expression. The induction of HO1 mRNA expression by G30 was independent from changes in medium insulin concentration, but was completely inhibited by a cocktail of antioxidants. In contrast to HO1, islet mRNA expression of glutathione peroxidase and constitutive haeme-oxygenase 2 were not affected by G30, nor by dibutyryl-cyclic-AMP.

CONCLUSION/INTERPRETATION

High glucose and dibutyryl-cyclic-AMP stimulate expression of HO1 in rat pancreatic beta cells. The inhibition of HO1 expression in G30 by nimodipine, clonidine, and antioxidants, suggests that Ca2+ influx and cyclic-AMP are necessary for the generation of oxidative stress by G30, or for the stimulation of beta-cell HO1 expression by increased oxidative stress.

Immunoprotective haem oxygenase induction by ultraviolet A (320-400 nm) radiation in the mouse is inhibited in interferon-gamma null mice

BACKGROUND

A protective role for the ultraviolet (UV) A waveband against immunosuppression induced by UVB (280-320 nm) radiation has been identified. The mechanism for UVA immunoprotection was found to involve two apparently unrelated mediators, the T-helper-1-associated proinflammatory cytokine interferon (IFN)-gamma and the UVA-induced redox-regulated stress protein, haem oxygenase (HO).

OBJECTIVES

To identify a relationship between these two immune regulators.

METHODS

The HO response to UVA radiation in the skin and liver was examined in mice with a targeted disruption of the IFN-gamma gene, known to be unresponsive to UVA photoimmunoprotection. Results IFN-gamma null mice did not respond to UVA irradiation with the normal upregulation of HO activity in either the irradiated skin or the liver. Injection of these mice with recombinant IFN-gamma previously shown to restore the UVA-photoimmunoprotective effect, here partially and dose-responsively restored their ability for induction of HO activity in both skin and liver following UVA irradiation.

CONCLUSIONS

IFN-gamma appears to be a prerequisite for the immunoprotective induction of HO, although other mediators may also be involved. The UVA responsiveness of HO in an internal organ such as the liver suggests the existence of a soluble UVA-induced mediator from the skin, which may be IFN-gamma.

Gene transfer of manganese superoxide dismutase extends islet graft function in a mouse model of autoimmune diabetes

Islet transplantation is a promising cure for diabetes. However, inflammation, allorejection, and recurrent autoimmune damage all may contribute to early graft loss. Pancreatic islets express lower levels of antioxidant genes than most other tissues of the body, and beta-cells in particular are sensitive to oxidative damage. Therefore, damage from oxidative stress may pose a major obstacle to islet replacement therapy in that both the islet isolation and transplantation processes generate oxygen radicals. To determine whether antioxidant gene overexpression in isolated pancreatic islets can prevent oxidative damage and prolong islet function after transplantation, we used the NOD mouse model to study oxidative stress encountered during both transplantation and autoimmune attack. We transferred an antioxidant gene, manganese superoxide dismutase (MnSOD), by adenoviral infection into isolated islets that were transplanted into streptozotocin-treated NODscid recipient mice. Functioning islet grafts were subsequently exposed to diabetogenic spleen cells and monitored until graft failure. The results show that islet grafts overexpressing MnSOD functioned approximately 50% longer than control grafts. This significant prolongation of graft function suggests that the antioxidant activity of MnSOD is beneficial to transplanted islet survival and may be used in combination with other strategies aimed at islet graft protection.

Effect of proinflammatory cytokines on gene expression of the diabetes-associated autoantigen IA-2 in INS-1 cells

Cytokines released from activated antigen-presenting cells and T-lymphocytes are crucially involved in the pathogenesis of type 1 diabetes. Previous studies have shown that proinflammatory cytokines play an important role in the induction of autoimmunity and beta-cell damage. Inhibition of insulin expression has been described, but their effects on other major target autoantigens, such as the tyrosine phosphatase-like protein IA-2, is not known. In the present study, we established sensitive real-time RT-PCR to measure IA-2, insulin, and inducible nitric oxide (NO) synthase (iNOS) mRNA expression. Rat insulinoma INS-1 cells were stimulated with IL-1beta, TNF-alpha, interferon (IFN)-gamma, and IL-2 as well as with two combinations of these cytokines (C1: IL-1beta + TNF-alpha + IFN-gamma; C2: TNF-alpha + IFN-gamma). Treatment with IL-1beta, TNF-alpha, or IFN-gamma alone caused a significant down-regulation of IA-2 and insulin mRNA levels in a time and dose-dependent manner, whereas IL-2 had no effect. Exposure to cytokine combinations strongly potentiates the inhibitory effects. Incubation of cells with C1 and C2 for 24 h induces a significant inhibition of IA-2 mRNA levels by 78% and 58%, respectively. Under these conditions, an up to 5 x 10(4)-fold increase of iNOS gene expression was observed. The hypothesis that the formation of NO is involved in IA-2 regulation was confirmed by the finding that the coincubation of C1 with 4 mM L-N(G)-monomethyL-L-arginine, an inhibitor of the iNOS, partly reversed the down-regulation of IA-2. Further, incubation with the synthetic NO-donor S-nitroso-N-acetyl-D-L-penicillamine significantly decreased IA-2 mRNA level to 51% of basal levels. In conclusion, we have demonstrated for the first time that IL-1beta, TNF-alpha, and IFN-gamma exert a strong inhibitory effect on expression of the diabetes autoantigen IA-2. The action of IL-1beta may be partly mediated by the activation of the NO pathway.

Heme oxygenase-1 induction in islet cells results in protection from apoptosis and improved in vivo function after transplantation

Transplantation of islets of Langerhans represents a viable therapeutic approach for the treatment of type 1 diabetes. Unfortunately, transplanted islets are susceptible to allogeneic recognition and rejection, recurrence of autoimmunity, and destruction by local inflammation at the site of implantation. The last of these phenomena might not only result in functional impairment and death of islet cells but could also contribute to amplifying the subsequent specific immune response. Induction of islet cell protection against inflammation could therefore be postulated to be a powerful means to improve overall graft fate. Heme oxygenase-1 (HO-1) has been described as an inducible protein capable of cytoprotection via radical scavenging and apoptosis prevention. The purpose of the present study was to analyze whether HO-1 upregulation in a beta-cell line and in freshly isolated murine islets could result in protection from apoptosis and improve in vivo functional performance. HO-1 upregulation was induced reproducibly with protoporphyrins and was correlated with protection from apoptosis induced in vitro with proinflammatory cytokines or Fas engagement. Furthermore, in vivo HO-1 upregulation resulted in improved islet function in a model of marginal mass islet transplantation in rodents. Strategies aimed at inducing HO-1 upregulation might result in improved success in islet transplantation.

Proteome analysis of interleukin-1beta--induced changes in protein expression in rat islets of Langerhans

The intracellular molecular events involved in the beta-cell death process are complex but poorly understood. Cytokines, e.g., interleukin (IL)-1beta, may play a crucial role in inducing this process. Protein synthesis is necessary for the deleterious effect of IL-1, and induction of both protective and deleterious proteins has been described. To characterize the rather complex pattern of islet protein expression in rat islets in response to IL-1, we have attempted to identify proteins of altered expression level after IL-1 exposure by 2D gel electrophoresis and mass spectrometry. Of 105 significantly changed (i.e., up- or downregulated or de novo-induced) protein spots, we obtained positive protein identification for 60 protein spots. The 60 identifications corresponded to 57 different proteins. Of these, 10 proteins were present in two to four spots, suggesting that posttranslatory modifications had occurred. In addition, 11 spots contained more than one protein. The proteins could be classified according to their function into the following groups: 1) energy transduction; 2) glycolytic pathway; 3) protein synthesis, chaperones, and protein folding; and 4) signal transduction, regulation, differentiation, and apoptosis. In conclusion, valuable information about the molecular mechanisms involved in cytokine-mediated beta-cell destruction was obtained by this approach.

Increased urinary excretion of bilirubin oxidative metabolites in septic patients: a new marker for oxidative stress in vivo

BACKGROUND

Bilirubin oxidative metabolites (BOMs) are generated from bilirubin as a result of its scavenging action against free radicals. During sepsis, excess amounts of free radicals are produced, and they play an important role in the pathophysiological process. We studied whether urinary excretion of BOMs would increase under septic conditions in humans and compared BOM levels with other well-established clinical parameters of inflammation.

METHODS

In 19 septic patients and 28 nonseptic control patients, the BOM concentrations in urine were measured by enzyme-linked immunosorbent assay with an anti-bilirubin antibody.

RESULTS

Urinary BOM levels in septic patients were much higher than those in control patients (21.6 +/- 2.5 vs 1.4 +/- 0.4 micromol/g creatinine, P < 0.001). Although there was a linear correlation between urinary BOM and serum total bilirubin levels (r = 0.392, P = 0.008), serum bilirubin levels were not significantly higher in the septic group than in the control group (P = 0.072). BOM levels correlated with body temperature (r = 0.801, P < 0.001), white blood cell counts in the peripheral blood (r = 0.590, P < 0.001), serum C-reactive protein (r = 0.653, P < 0.001), and the acute physiological and chronic health evaluation (APACHE II) score (r = 0.467, P = 0.003).

CONCLUSIONS

These results demonstrated a urinary increase in BOMs in septic patients. This increase indicates that urinary BOM level is a possible marker for continuous monitoring of sepsis severity in clinical practice.

The stressed synovium

This review focuses on the mechanisms of stress response in the synovial tissue of rheumatoid arthritis. The major stress factors, such as heat stress, shear stress, proinflammatory cytokines and oxidative stress, are discussed and reviewed, focusing on their potential to induce a stress response in the synovial tissue. Several pathways of stress signalling molecules are found to be activated in the synovial membrane of rheumatoid arthritis; of these the most important examples are heat shock proteins, mitogen-activated protein kinases, stress-activated protein kinases and molecules involved in the oxidative stress pathways. The expression of these pathways in vitro and in vivo as well as the consequences of stress signalling in the rheumatoid synovium are discussed. Stress signalling is part of a cellular response to potentially harmful stimuli and thus is essentially involved in the process of synovitis. Stress signalling pathways are therefore new and promising targets of future anti-rheumatic therapies.

Heme oxygenase-1 and NADPH cytochrome P450 reductase expression in experimental allergic encephalomyelitis: an expanded view of the stress response

Oxidative stress is implicated in the pathogenesis of experimental allergic encephalomyelitis (EAE), a model for multiple sclerosis. Heme oxygenase-1 (HO-1) is a heat shock protein induced by oxidative stress. HO-1 metabolizes the pro-oxidant heme to the antioxidant biliverdin and CO. HO-1 requires electrons, donated by NADPH cytochrome P450 reductase (henceforth, reductase), for catalytic activity. EAE was induced with a peptide of proteolipid protein in SJL mice, and the expression of HO-1 and reductase in the hindbrain was analyzed. HO-1 protein levels were significantly increased in EAE animals compared with control mice. HO-1 expression was present in ameboid macrophages, reactive microglia, and astrocytes in white matter tracks. Bergmann glia and ameboid macrophages also were occasionally stained in the molecular layer of the cerebellum. Unlike HO-1, reductase protein levels decreased with disease severity. HO-1 and reductase were associated with each other in endoplasmic reticulum micelles, suggesting that the decrease in reductase does not interfere with its association with HO-1. In cells that express HO-1, the association of reductase with HO-1 should competitively inhibit the interaction of reductase with cytochrome P450 isozymes and thereby limit free radical production as the latter two enzymes act cooperatively to produce superoxide. The increase in HO-1 together with the decrease in reductase may be part of a common defense mechanism attempting to minimize tissue damage in several neurological conditions.

Pretransplant induction of HSP-70 in isolated adult pig islets decreases early islet xenograft survival

The heat-induced HSP-70 expression protects rat islet single cells against lysis mediated by nitric oxide (NO), reactive oxygen, and streptozotocin. The present study was performed to investigate the potential antiinflammatory effect of pretransplant heat shock in adult pig islets for subsequent early islet xenograft survival. Maximum HSP-70 expression in freshly isolated pig islets was induced by hyperthermia at 43 degrees C for 90 min prior to islet regeneration at 37 degrees C for 4-6 h. Heat-stressed and sham-treated islets were incubated in 0.6 mM H2O2 or 1.5 mM Na-nitroprusside at 37 degrees C for 20 h. Early graft survival was evaluated in normoglycemic Lewis rats after simultaneous, contralateral transplantation of heat-shocked islets and sham-treated islets into the renal subcapsular space of the same recipient. Prior hyperthermia significantly reduced specific lysis of islets exposed to NO or H2O2, although protection was only marginal. No differences were observed between viability of heat-shocked and sham-treated islets after NO exposure. In contrast, prior heat shock increased islet viability after H2O2 treatment. The finding that hyperthermia reduced recovery of initially grafted pig insulin 48 h after transplantation by 30% compared to controls contrasted significantly with an increased insulin recovery in heat-exposed islets at the end of simultaneous 37 degrees C culture. The observation, that the heat-induced HSP-70 expression decreases early islet xenograft survival as reflected by recovery of grafted insulin, implies an enhancement of islet immunogenicity and the induction of apoptosis. Future experiments aiming at augmentation of intrinsic defense mechanisms should consider detrimental effects associated with induction of heat shock proteins.

Novel experimental strategies to prevent the development of type 1 diabetes mellitus

Type 1 diabetes is an autoimmune disease leading to extensive destruction of the pancreatic beta-cells. Our research focusses on the role of beta-cells during the course of the disease, aiming at finding novel strategies to enhance beta-cell resistance against the cytotoxic damage inflicted by the immune system. Special attention has been paid to the possibility that cytokines released by the immune cells infiltrating the pancreatic islets can directly suppress and kill beta-cells. Certain cytokines (interleukin-1beta, tumor necrosis factor-alpha and interferon-gamma) either alone or in combination, are able to activate signal transduction pathways in beta-cells leading to transcription factor activation and de novo gene expression. In this context, it has been found that induction of inducible nitric oxide synthase mediates an elevated production of nitric oxide, which impairs mitochondrial function and causes DNA damage eventually leading to apoptosis and necrosis. However, other induced proteins SUCH AS heat shock protein 70 and superoxide dismutase may reflect a defense reaction elicited in the beta-cells by the cytokines. Our strategy is to further seek for proteins involved in both destruction and protection of beta-cells. Based on this knowledge, we plan to apply gene therapeutic approaches to increase expression of protective genes in beta-cells. If this is feasible we will then evaluate the function and survival of such modified beta-cells in animal models of type 1 diabetes such as the NOD mouse. The long-term goal for this research line is to find novel approaches to influence beta-cell resistance in humans at risk of developing type 1 diabetes.

Detection of heat shock protein 70 (Hsp70) and anti-Hsp70 antibodies in the serum of normal individuals

Heat shock or stress proteins (Hsp) are typically regarded as being intracellular proteins that have a range of functions including the maintenance of cellular integrity. Members of the Hsp70 family of molecules have been implicated in the processing and presentation of antigen and the cross reactivity of lymphocytes specific for pathogen-derived heat shock proteins with self Hsp70 has been suggested to be an underlying cause of certain autoimmune diseases. This study reports the presence of soluble Hsp70 in the peripheral circulation of normal individuals. Concentrations of soluble Hsp70 in females were approximately twice those in males. Circulating anti-Hsp70 antibodies were detected in all individuals assessed, but there were no differences between males and females. However, there was a significant correlation between soluble Hsp70 concentration and antibody levels in males, but not females. The physiological role for circulating heat shock proteins is intriguing, but currently unknown. These findings extend our previous observations that Hsp60 is present in the peripheral circulation and support the proposition that soluble heat shock proteins may play a regulatory role in either the prevention or protection of pathophysiological processes involving inadvertent immunorecognition or cross-recognition of heat shock proteins.

A protective role for heme oxygenase expression in pancreatic islets exposed to interleukin-1beta

Heme oxygenase (HO)-1 expression was investigated in rat isolated pancreatic islets. Freshly isolated islets showed no evidence of HO-1 expression. After a 20-h culture, there was a small increase in HO-1 in control islets, and interleukin-1beta (IL-1beta) induced HO-1 expression above control levels. N(G)-monomethyl-L-arginine inhibited the IL-1beta-induced increase in HO-1. Sodium nitroprusside-generated nitric oxide also increased HO-1 expression. CoCl2 induced a concentration- and time-dependent increase in HO-1, but not heat shock protein 70, expression. Cobalt chloride (CoCl2) protected islets from the inhibitory effects of IL-1beta on glucose-stimulated insulin release and glucose oxidation. Nickel chloride did not mimic the effects of CoCl2. An inhibitor of HO-1 activity, zinc-protoporphyrin IX (ZnPP), prevented the protective effect of CoCl2 on insulin release with IL-1beta but did not affect HO-1 expression or the inhibitory response to IL-1beta alone. ZnPP also inhibited the protective effect of hemin in IL-1beta-treated islets. CoCl2 inhibited the marked increase in islet nitrite production in response to IL-1beta. Cobalt-protoporphyrin IX (CoPP), which increased HO expression and activity, also protected islets from the inhibitory effects of IL-1beta, even though IL-1beta largely blocked the CoPP-induced increase in HO-1 expression. In betaHC9 cells, CoCl2 increased HO-1 expression and HO activity, whereas CoPP directly activated HO. ZnPP inhibited basal and CoCl2-stimulated HO activity. Thus, increased HO-1 expression and/or HO activity in response to CoCl2, CoPP, and hemin, seems to mediate protective responses of pancreatic islets against IL-1beta. HO-1 may be protective of beta-cells because of the scavenging of free heme, the antioxidant effects of the end-product bilirubin, or the generation of carbon monoxide, which might have insulin secretion-promoting effects and inhibitory effects on nitric oxide synthase.

Enhanced expression of heat shock protein 70 (hsp70) and heat shock factor 1 (HSF1) activation in rheumatoid arthritis synovial tissue. Differential regulation of hsp70 expression and hsf1 activation in synovial fibroblasts by proinflammatory cytokines, shear stress, and antiinflammatory drugs

Heat shock proteins (hsp) have been repeatedly implicated to participate in the pathogenesis of rheumatoid arthritis (RA). Herein, we investigated the regulation of synovial hsp70 expression by analyzing the DNA-binding activity of heat shock transcription factor 1 (HSF1) as well as inducible hsp70 expression. Experiments were performed both on synovial tissue and on synovial fibroblast-like cells (SFC). Gel mobility shift analysis revealed increased HSF1 activation, and Western blotting and immunohistochemistry revealed increased hsp70 expression in RA synovial tissue, but not in synovial tissue derived from patients with osteoarthritis. Proinflammatory cytokines (TNF-alpha, IL-1alpha, IL-6), but not IFN-gamma or TGF-beta, induced activation of HSF1-DNA binding and hsp70 expression in cultivated SFC. Activation of HSF1 in SFC was accompanied by hyperphosphorylation and nuclear translocation of HSF1. Furthermore, shear stress also induced a complete heat shock response in cultivated synovial cells. In contrast, nonsteroidal antiinflammatory drugs triggered only an incomplete heat shock response, with HSF1 activation but not hsp70 induction, whereas steroids and immunosuppressive drugs did not affect the heat shock response at all. In summary, these data suggest that induction of hsp70 expression in rheumatoid synovial tissue is based on transcriptional activation of HSF1 due to the presence of proinflammatory cytokines (and possibly also shear stress).

Thiol redox modulation of tumor necrosis factor-alpha responsiveness in cultured AIDS-related Kaposi's sarcoma cells

Both clinical and experimental evidence indicates that AIDS-related Kaposi's sarcoma (AIDS-KS) has a multifactorial pathogenesis with factors such as HIV viral load, latent virus induction, and opportunistic infections contributing to disease progression. However, a consistent feature that unites these apparently diverse putative etiologic agents is sustained serum elevations of pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha). While virtually every cell responds to TNF-alpha with gene activation, the extent of TNF-alpha-mediated cellular signaling is regulated by a delicate balance between signal activation and signal arresting events. Reactive oxygen intermediates (ROI), which are generated as a consequence of TNF-alpha membrane interaction, are part of this TNF-alpha-initiated cellular activation cascade. Previous studies in our laboratory have shown that AIDS-KS cells possess impaired oxygen intermediate scavenging capacities, thereby establishing conditions permissive for the intracellular retention of ROI. In this study, we used cellular capacity to upregulate the cytoprotective enzyme superoxide dismutase (SOD) to address the extent of cellular response to TNF-alpha. Concurrent with the SOD analyses, nucleotide profiles were obtained to assess cellular bioenergetic responses during TNF-alpha challenge. Proliferative growth levels of mitochondrial (Mn)SOD activities showed an activity spectrum ranging from lowest activity in AIDS-KS cells, to intermediate levels in matched, nonlesional cells from the AIDS-KS donors, to highest activities in HIV normal fibroblasts. In contrast, following TNF-alpha challenge, the AIDS-KS and KS donor nonlesional cells showed a 11.89- and 5.86-fold respective increase in MnSOD activity, while the normal fibroblasts demonstrated a 1.35-fold decrease. Subsequent thiol redox modulation studies showed that only the normal fibroblast cultures showed a potentiation of TNF-alpha-mediated MnSOD upregulation following GSH depletion. In addition, provision of the GSH precursor, N-acetylcysteine during TNF-alpha challenge only diminished MnSOD activity and mitochondrial compartmentalization in the AIDS-KS cells, a finding that likely reflects the lower levels of reduced thiols in this cellular population. Our data, which show that a perturbation in their cellular thiol redox status accentuates AIDS-KS cellular responsiveness to TNF-alpha, suggest a biochemical rationale for the recognized TNF-alpha AIDS-KS clinical correlation.

The harmony of the spheres: inducible nitric oxide synthase and related genes in pancreatic beta cells

The radical nitric oxide (NO) is a possible mediator of pancreatic beta-cell damage in insulin-dependent diabetes mellitus (IDDM). NO is produced by the enzyme nitric oxide synthase (NOS), in a reaction where arginine is the main substrate. There are different isoforms of NOS, but in the context of immune mediated beta-cell damage the inducible form of NOS (iNOS) is the most relevant. The beta-cell iNOS is similar and encoded by the same gene on chromosome 17 as the iNOS expressed in macrophages and other nucleated cells. iNOS activation depends on gene transcription and de novo enzyme synthesis, and NO seems to induce a negative feedback on iNOS expression. While iNOS mRNA is induced by interleukin-1 beta (IL-1 beta) alone in rodent insulin-producing cells, a combination of two (IL-1 beta + interferon gamma) (IFN-gamma) or three (IL-1 beta + IFN gamma + tumour necrosis factor alpha) cytokines is required for iNOS activation in human pancreatic islets. The promoter region of the murine iNOS gene has at least 25 binding sites for different transcription factors, and the nuclear transcription factor kappa B is necessary for cytokine-induced iNOS transcription in both rodent and human pancreatic islets. The nature of other transcription factors relevant for iNOS regulation in these cells remains to be determined. Induction of iNOS is paralleled by induction of several other cytokine-dependent genes in beta cells, including argininosuccinate synthetase, cyclooxygenase and manganese superoxide dismutase. Some of these genes may contribute to beta-cell damage, while others are probably involved in beta-cell defence and/or repair. Regulation of iNOS and other related genes in beta cells is complex, and differs in several aspects from that observed in macrophages. There are also important differences in iNOS regulation between rodent and human pancreatic islets. A detailed knowledge of the molecular regulation of these genes in beta cells may be instrumental in the development of new approaches to prevent beta-cell destruction in early IDDM.