Protective Effect Of Interleukin-6 Research Articles

2126-P: Investigating the Regulation of Autophagy and the Antioxidant Response by IL-6 Family Cytokines

Pathways that mitigate cellular stress are critical for pancreatic beta cell function and survival. We have reported that the cytokine interleukin-6 (IL-6) coordinately activates two such pathways, autophagy and the antioxidant response, resulting in decreased oxidative stress and increased beta cell survival under diabetogenic conditions. Our investigation of this protective effect of IL-6 on the beta cells subsequently revealed that members of the IL-6 family of cytokines stimulated the mitochondrial translocation of NRF2, the central antioxidant regulator. This was surprising since NRF2 is well-characterized as a transcription factor. Under these conditions, we also observe translocation of another transcription factor, STAT3, to the mitochondria, consistent with previously published observations. Here, we present data to validate these findings in the islet in vivo and investigate the downstream events associated with NRF2 mitochondrial translocation. We used a mouse model where animals were intraperitoneally injected with either IL-6 or another IL-6 family member, leukemia inhibitory factor (LIF), and pancreata were collected at 30 minutes post-injection. We then used immunofluorescence analysis of paraffin tissue sections. We observed that both IL-6 and LIF rapidly elicit a reduction in the autophagy receptor p62 both in the cytosol and at the mitochondria when compared to saline-injected mice. This suggests that both global autophagy and selective mitophagy are stimulated in the beta cell by both IL-6 and LIF. Furthermore, as both IL-6 and LIF selectively stimulate mitochondrial but not nuclear translocation of NRF2, our data suggests that NRF2 may play a role in the stimulation of mitophagy by IL-6 family cytokines. Further studies investigating the requirement of NRF2 for beta cell mitophagy under conditions of beta cell stress response will shed light on this novel pathway of the cellular antioxidant response. Disclosure M. Marasco: Employee; Spouse/Partner; Eli Lilly and Company. Z. Akbar: None. J. Crowder: Employee; Spouse/Partner; Eli Lilly and Company. A. Novak: None. C. Muralidharan: None. M. Arvin: None. A.K. Linnemann: None. Funding National Institutes of Health (T32DK064466-16, R03DK115990)

Protective effects of interleukin-6 in lipopolysaccharide (LPS)-induced experimental endotoxemia are linked to alteration in hepatic anti-oxidant enzymes and endogenous cytokines

Endogenous interleukin-6 has been considered as an important anti-inflammatory cytokine controlling both local and systemic acute inflammatory responses; the usefulness of IL-6 in endotoxemia aiming to block the production of reactive oxygen species and the release of inflammatory cytokines is under discussion The aim of the study was to evaluate the protective effects of IL-6 in experimentally induced endotoxemia in mice correlating the changes in tissue anti-oxidant enzymes and circulating cytokines. Liver injury in low-dose bacterial lipopolysaccharide (5 μg/mouse)-induced endotoxemic mice receiving IL-6 (300 ng/mouse) treatment either before or after LPS injection was detected by the estimation of serum oxaloacetate transaminase and serum glutamate pyruvate transaminase. This finding supports that liver injury during experimental endotoxemia could be lowered by IL-6. Current data also demonstrate the critical role of IL-6 in inducing SOD in liver, whereas IL-6 prior and after LPS challenge group showed reduced PMN infiltration in the liver as evident by decreased hepatic MPO content in those mice. IL-6 treatment also showed higher IL-10 production in serum than endotoxic group as IL-10 is a potent and pleiotropic anti-inflammatory cytokine that inhibits the synthesis of pro-inflammatory cytokines and also has a suppressive effect on pro-inflammatory cytokine like TNF-α, IFN-γ and IL-12. It is also directly involved in the modulation of other aspects of inflammation, particularly cytokine responses and inflammatory cell infiltration.

GP130-STAT3 Regulates Epithelial Cell Migration and Is Required for Repair of the Bronchiolar Epithelium

Following injury, bronchiolar cells undergo rapid squamous metaplasia, followed by proliferation and re-establishment of the complex columnar epithelium that is characteristic of the normal airway. Mechanisms that regulate the repair of bronchiolar epithelium are of considerable relevance for understanding the pathogenesis of both acute and chronic lung diseases associated with airway remodeling. This study was designed to identify the role of the GP130-STAT3 signaling pathway during repair of the bronchiolar epithelium. STAT3 (signal transducer and activator of transcription 3) and GP130 (glycoprotein 130) were each selectively deleted from the pulmonary epithelial cells of transgenic mice in vivo, producing Stat3(Delta/Delta) and Gp130(Delta/Delta) mice, respectively. Airway injury was induced in adult mice by administration of naphthalene, a toxicant of nonciliated respiratory epithelial cells (Clara cells). Nuclear STAT3 staining was induced in bronchiolar epithelial cells following naphthalene-mediated injury in control (Stat3(flox/flox)) mice. Whereas nearly complete repair of the bronchiolar epithelium was observed in control mice within 13 days, restoration of cell shape, cell density, and the pattern of ciliated and nonciliated cells did not occur in the peripheral bronchioles of either Stat3(Delta/Delta) or Gp130(Delta/Delta) mice. Expression of dominant-negative STAT3 inhibited airway epithelial cell migration during repair in vitro; wild-type STAT3 expression activated such migration. In the present study, we show that GP130-STAT3 signaling functions in a cell-autonomous manner to restore cell shape and numbers required for repair of the bronchiolar epithelium following injury.

Maintaining the Integrity of the Intestinal Epithelial Cell Barrier

The cytokine IL-6 (interleukin-6), which has both pro- and antiinflammatory properties, helps to maintain epithelial barrier function in the intestine. Members of a family of structural proteins called keratins form the intermediate filaments in the cytoskeleton of epithelial cells and have been shown to protect cells from injury. A mutation in keratin-8 is found in some patients with inflammatory bowel disease, and mice deficient in keratin-8 develop colonic problems. Wang et al . uncovered a connection between IL-6 and keratins, particularly keratin-8, in studies performed using a human colonic epithelial cell line and IL-6 knockout mice. Treatment of Caco2-BBE cells with IL-6 increased both keratin-8 and keratin-18 at the level of mRNA and protein. The authors used confocal microscopy to show that IL-6 increased these keratins in the subapical region of Caco2-BBE epithelia. Analysis with phosphospecific antibodies showed that IL-6 treatment increased keratin-8 phosphorylation, which is important for the regulation of keratin organization and function. By monitoring the permeability of Caco2-BBE epithelia to fluorescein isothiocyanate-dextran, the authors showed that IL-6 treatment resulted in decreased permeability of the epithelial barrier. Experiments using RNA interference showed that this decreased permeability was mediated by keratin-8, although loss of keratin-8 had no effect on epithelial permeability in the absence of IL-6. IL-6-deficient mice treated with dextran sodium sulfate showed increased intestinal permeability in comparison with wild-type mice. Together, these data implicate keratin-8 in mediating the protective effects of IL-6 on the integrity of the intestinal epithelial layer. L. Wang, S. Srinivasan, A. L. Theiss, D. Merlin, S. V. Sitaraman, Interleukin-6 induces keratin expression in intestinal epithelial cells. J. Biol. Chem. 282 , 8219-8227 (2007). [PubMed]

Interleukin-6 protects LNCaP cells from apoptosis induced by androgen deprivation through the Stat3 pathway.

Elevated expression of interleukin-6 (IL-6) is implicated in the progression of hormone refractory prostate cancer. Previous studies demonstrated that IL-6 promotes androgen-independent growth of prostate cancer cells. In this study, the effect of IL-6 on apoptosis induced by androgen deprivation was investigated. The effect of IL-6 on apoptosis induced by androgen deprivation in LNCaP cells was examined by cell death ELISA and Western blot using cleaved poly (ADP-ribose) polymerase (PARP) and caspase-9, as well as Bcl-xL and phosphorylated Bad. The Stat3 in IL-6-mediated anti-apoptosis in prostate cancer cells was examined using either dominant-negative or constitutively activated Stat3 mutants. Overexpression of IL-6 renders androgen sensitive LNCaP human prostate cancer cells more resistant to apoptosis induced by androgen deprivation. LNCaP cells undergo apoptosis after 72 hr of androgen deprivation, an outcome is largely absent in clones overexpressing IL-6 as measured by cell death ELISA and chromatin degradation assays. IL-6 over-expressing cells resulted in a significant decrease in the expression of cleaved PARP and cleaved caspase-9 as well as an increase in the expression of Bcl-xL and phosphorylated Bad. Addition of IL-6 antibody completely abolished the anti-apoptotic activity of IL-6. This protective effect of IL-6 was reversed by the expression of a dominant-negative Stat3 mutant, Stat3F. Furthermore, ectopic expression of a constitutively active Stat3 antagonized androgen deprivation-induced cell death of LNCaP cells. These results indicate that IL-6 protects androgen sensitive LNCaP cells from apoptosis induced by androgen deprivation, and Stat3 activation play an important role in IL-6-mediated anti-apoptosis in prostate cancer cells.

Interleukin-6 protects skin lesion caused by 7,12-dimethylbenz[a]anthracene.

Interleukin-6 (IL-6) regulates essential physiological functions such as acute phase reaction, immune response and hematopoiesis. We here studied possible protective effects of IL-6 on skin damage caused by 7,12-dimethylbenz[a]anthracene (DMBA) by using IL-6 null mice. The mice were topically applied with a single dose of DMBA (500 microg /mouse) on the dorsal skin. Osmotic pumps filled with recombinant human IL-6 (rhIL-6) were implanted subcutaneously on the ventral side of the mice. Control mice received PBS instead of rhIL-6 by the pump. Severe skin damage was observed in IL-6-null mice, whereas only epidermal hyperplasia was observed in the wild-type mice. Recombinant hIL-6 treatment to DMBA-treated IL-6-null mice suppressed the occurrence of the skin damage, indicating.

Interleukin-6 inhibits neurotransmitter release and the spread of excitation in the rat cerebral cortex.

Cytokines are extracellular mediators that have been reported to affect neurotransmitter release and synaptic plasticity phenomena when applied in vitro. Most of these effects occur rapidly after the application of the cytokines and are presumably mediated through the activation of protein phosphorylation processes. While many cytokines have an inflammatory action, interleukin-6 (IL-6) has been found to have a neuroprotective effect against ischaemia lesions and glutamate excitotoxicity, and to increase neuronal survival in a variety of experimental conditions. In this paper, the functional effects of IL-6 on the spread of excitation visualized by dark-field/infrared videomicroscopy in rat cortical slices and on glutamate release from cortical synaptosomes were analysed and correlated with the activation of the STAT3, mitogen-activated protein kinase ERK (MAPK/ERK) and stress-activated protein kinase/cJun NH2-terminal kinase (SAPK/JNK) pathways. We have found that IL-6 depresses the spread of excitation and evoked glutamate release in the cerebral cortex, and that these effects are accompanied by a stimulation of STAT3 tyrosine phosphorylation, an inhibition of MAPK/ERK activity, a decreased phosphorylation of the presynaptic MAPK/ERK substrate synapsin I and no detectable effects on SAPK/JNK. The effects of IL-6 were effectively counteracted by treatment of the cortical slices with the tyrosine kinase inhibitor lavendustin A. The inhibitory effects of IL-6 on glutamate release and on the spread of excitation in the rat cerebral cortex indicate that the protective effect of IL-6 on neuronal survival could be mediated by a downregulation of neuronal activity, release of excitatory neurotransmitters and MAPK/ERK activity.

P-486 - Protective effect of interleukin-6 against the death of PC 12 cells caused by 4-hydroxynonenaI toxicity

P-486 - Protective effect of interleukin-6 against the death of PC 12 cells caused by 4-hydroxynonenaI toxicity

Ischemia impairs liver regeneration after major tissue loss in rodents: protective effects of interleukin-6.

The effects of ischemia on the regenerative capacity of the liver after major tissue loss remain unclear. Interleukin-6 (IL-6) has been shown to confer protection in models of normothermic ischemia and reperfusion injury and to initiate hepatocyte proliferation after major hepatectomy. Therefore, we investigated the effects of ischemia on the regenerative capacity of the liver and evaluated the role of IL-6 in reducing reperfusion injury and enhancing hepatic proliferation in models combining ischemia and major hepatectomy. Rats subjected to 70% hepatectomy and 30 minutes of hepatic ischemia showed significantly reduced regenerative capacity (mitotic index, proliferating cell nuclear antigen, and regenerated liver weight) when compared with animals subjected to hepatectomy alone. Pretreatment of animals subjected to hepatectomy and ischemia with recombinant interleukin-6 (rIL-6) completely restored each parameter of regeneration to levels comparable with those of animals subjected to hepatectomy only. Similar results were obtained in IL-6 deficient (IL-6(-/-)) mice. IL-6(-/-) mice exposed to ischemia and hepatectomy showed impaired hepatic regeneration when compared with wild-type mice subjected to the same experimental conditions. The use of rIL-6 completely corrected each parameter of regeneration showing the specificity of IL-6 in this type of injury. The impact of IL-6 on animal survival was studied in a model combining 45 minutes of ischemia and 68% hepatectomy. Five of 7 (71%) animals pretreated with rIL-6 survived permanently, whereas all control animals died within 3 days of surgery (P =.02, Fisher's exact test). In conclusion, the study shows that ischemia dramatically impairs the regenerative capacity of the liver. IL-6 appears to be a key protective molecule in reducing injury and promoting regeneration following combined ischemia and major tissue loss.

Protective effect of interleukin-6 against the death of PC12 cells caused by serum deprivation or by the addition of a calcium ionophore

Interleukin-6 (IL-6) is known to differentiate the rat pheochromocytoma cell line PC12 to neuron-like cells. We examined the effect of IL-6 on the death of PC 12 cells. IL-6 significantly blocked the death of PC12 cells by serum deprivation. The protective effect of IL-6 was increased by preincubation of PC12 with IL-6 for 20 hr before serum deprivation. The inhibition of protein synthesis by cycloheximide had no effect on the protective effect of IL-6 on the serum deprivation-induced cell death. IL-6 also inhibited the death of PC12 cells induced by addition of the calcium ionophore A23187 to the culture medium. Specific in situ labeling of DNA cleavage was observed in PC12 cells subjected to both serum deprivation and A23187 for 24 hr. IL-6 inhibited DNA fragmentation in PC12 cells following serum deprivation. These results suggest that the death of PC12 cells induced by serum deprivation or by the addition of calcium ionophore is apoptosis, and that IL-6 blocks apoptosis of PC12 cells.

Effect of metals on interleukin-6 (IL-6) mitogenic stimulation of murine hybridoma cells.

The effect of several divalent metal cations (Co, Cu, Zn, Hg and Pb) on the proliferative response of B9 hybridoma cells to IL-6 has been investigated. At concentrations which are not cytotoxic all the metals inhibited proliferation. The inhibition by Cd and Pb was dependent on both time of addition of the metal and IL-6 concentration. Cd (10 microM) and Pb (50 microM) added at the same time as IL-6 were inhibitory but added 24h later had no effect. Increasing the concentration of IL-6 overcame the inhibitory effect of Cd (10 microM) and Pb (50 microM). Inhibition caused by the other metals was independent of either time of addition or IL-6 concentration. IL-6 did not stimulate an increased intracellular concentration of metallothionein suggesting that the protective effect of IL-6 is not mediated via induction of metallothionein. The results suggest that there are at least two distinct metal sensitive events in B9 proliferation, i) IL-6 reversible inhibition by Cd and Pb ii) IL-6 independent inhibition by Co, Cu and Hg.