Pioglitazone, a PPARgamma ligand, suppresses NFkappaB activation through inhibition of IkappaB kinase activation in cerulein-treated AR42J cells

Pitfalls in AR42J-model of cerulein-induced acute pancreatitis

Background

AR42J are immortalized pancreatic adenocarcinoma cells that share similarities with pancreatic acinar cells. AR42J are often used as a cell-culture model of cerulein (CN)-induced acute pancreatitis (AP). Nevertheless, it is controversial how to treat AR42J for reliable induction of AP-like processes. Gene knockout and/or overexpression often remain challenging, as well. In this study, we demonstrate conditions for a reliable induction of proinflammatory markers upon CN treatment in AR42J and high transfection efficacy using Glyoxalase-I (Glo-I) as a target of interest.

Methods

Effects of dexamethasone (dexa) and CN on cell morphology and amylase secretion were analyzed via ELISA of supernatant. IL-6, TNF-α and NF-κB-p65 were measured via qRT-PCR, ELISA and Western Blot (WB). Transfection efficacy was determined by WB, qRT-PCR and immune fluorescence of pEGFP-N1-Glo-I-Vector and Glo-I-siRNA.

Results

Treatment of AR42J with 100 nm dexa is mandatory for differentiation to an acinar-cell-like phenotype and amylase production. CN resulted in secretion of amylase but did not influence amylase production. High levels of CN-induced amylase secretion were detected between 3 and 24 hours of incubation. Treatment with LPS alone or in combination with CN did not influence amylase release compared to control or CN. CN treatment resulted in increased TNF-α production but not secretion and did not influence IL-6 mRNA. CN-induced stimulation of NF-κB was found to be highest on protein levels after 6h of incubation. Transient transfection was able to induce overexpression on protein and mRNA levels, with highest effect after 12 to 24 hours. Gene-knockdown was achieved by using 30 pmol of siRNA leading to effective reduction of protein levels after 72 hours. CN did not induce amylase secretion in AR42J cell passages beyond 35.

Conclusion

AR42J cells demonstrate a reliable in-vitro model of CN-induced AP but specific conditions are mandatory to obtain reproducible data.

Pioglitazone/microRNA‑141/FOXA2: A novel axis in pancreatic β‑cells proliferation and insulin secretion

MicroRNAs (miRs) are considered to be effective, post‑transcriptional regulators in the pathophysiology of type 2 diabetes (T2D) and promising treatment targets. However, the function of miR‑141 remains to be elucidated. In the present study, upregulation of miR‑141 was demonstrated in diabetic mice and elderly diabetic patients. Using reverse transcriptase‑quantitative polymerase chain reaction, luciferase reporter assays and western blotting, forkhead box A2 (FOXA2) was identified as a direct target gene of miR‑141. The potential role of miRNA‑141 or FOXA2 was evaluated by overexpressing or silencing miR‑141 or FOXA2, respectively. The increased expression of miR‑141 resulted in impaired glucose‑stimulated insulin secretion (GSIS) and INS‑1 β cell proliferation. In addition, miR‑141 silencing in MIN6 pseudoislets or INS‑1 β cells led to reduced T2D‑associated damage. Furthermore, the expression of miR‑141 may be corrected by treatment with pioglitazone, which is widely used for insulin resistance therapy. The present study also demonstrated the mechanism by which miR‑141 regulated GSIS and proliferation through FOXA2. Overexpression of FOXA2 in MIN6 pseudoislets increased the effect of the miR‑141 inhibitor on GSIS. FOXA2 effectively reversed the effect of miR‑141 overexpression on β cell proliferation. In conclusion, the results of the present study indicate that the pioglitazone/miR‑141/FOXA2 axis may represent a promising target mechanism for T2D treatment.

Recombinant Netrin-1 binding UNC5B receptor attenuates neuroinflammation and brain injury via PPARγ/NFκB signaling pathway after subarachnoid hemorrhage in rats

Neuroinflammation is an essential mechanism involved in the pathogenesis of subarachnoid hemorrhage (SAH)-induced brain injury. Recently, Netrin-1 (NTN-1) is well established to exert anti-inflammatory property in non-nervous system diseases through inhibiting infiltration of neutrophil. The present study was designed to investigate the effects of NTN-1 on neuroinflammation, and the potential mechanism in a rat model of SAH. Two hundred and ninety-four male Sprague Dawley rats (weight 280-330 g) were subjected to the endovascular perforation model of SAH. Recombinant human NTN-1 (rh-NTN-1) was administered intravenously. Small interfering RNA (siRNA) of NTN-1 and UNC5B, and a selective PPARγ antagonist bisphenol A diglycidyl ether (BADGE) were applied. Post-SAH evaluations included neurobehavioral function, brain water content, Western blot analysis, and immunohistochemistry. Our results showed that endogenous NTN-1 and its receptor UNC5B level were increased after SAH. Administration of rh-NTN-1 reduced brain edema, ameliorated neurological impairments, and suppressed microglia activation after SAH, which were concomitant with PPARγ activation, inhibition of NFκB, and decrease in TNF-α, IL-6, and ICAM-1, as well as myeloperoxidase (MPO). Knockdown of endogenous NTN-1 increased expression of pro-inflammatory mediators and MPO, and aggravated neuroinflammation and brain edema. Moreover, knockdown of UNC5B using specific siRNA and inhibition of PPARγ with BADGE blocked the protective effects of rh-NTN-1. In conclusion, our findings indicated that exogenous rh-NTN-1 treatment attenuated neuroinflammation and neurological impairments through inhibiting microglia activation after SAH in rats, which is possibly mediated by UNC5B/PPARγ/NFκB signaling pathway. Exogenous NTN-1 may be a novel therapeutic agent to ameliorating early brain injury via its anti-inflammation effect.

An Anti-Inflammatory PPAR-γ Agonist from the Jellyfish-Derived Fungus Penicillium chrysogenum J08NF-4

An investigation of the jellyfish-derived fungus Penicillium chrysogenum J08NF-4 led to the isolation of two new meroterpene derivatives, chrysogenester (1) and 5-farnesyl-2-methyl-1-O-methylhydroquinone (2), and four known farnesyl meroterpenes. Docking analysis of 1 showed that it binds to PPAR-γ in the same manner as the natural PPAR-γ agonist amorfrutin B (7). Compound 1 activated PPAR-γ in murine Ac2F liver cells and increased nuclear PPAR-γ protein levels in murine RAW 264.7 macrophages. Because one of the main biological functions of PPAR-γ agonists is to suppress inflammatory response, an in vitro study was performed to explore the anti-inflammatory potency of 1 and the mechanism involved. In RAW 264.7 macrophages, 1 inhibited phosphorylation of the NF-κB p65 subunit and suppressed the expression of the pro-inflammatory mediators iNOS, NO, COX-2, TNF-α, IL-1β, and IL-6. We propose 1 suppresses inflammatory responses by activating PPAR-γ and subsequently downregulating the NF-κB signaling pathway, thus reducing the expressions of pro-inflammatory mediators.

Yin-Chen-Hao Tang Attenuates Severe Acute Pancreatitis in Rat: An Experimental Verification of In silico Network Target Prediction

Yin-Chen-Hao Tang (YCHT) is a classical Chinese medicine compound that has a long history of clinical use in China for the treatment of inflammatory diseases. However, the efficacy and mechanisms of YCHT for the treatment of severe acute pancreatitis (SAP) are not known. The current study investigated the pharmacological properties of YCHT against SAP and its underlying mechanisms. A computational prediction of potential targets of YCHT was initially established based on a network pharmacology simulation. The model suggested that YCHT attenuated SAP progress by apoptosis inducement, anti-inflammation, anti-oxidation and blood lipid regulation. These effects were validated in SAP rats. YCHT administration produced the following results: (1) significantly inhibited the secretion of pancreatic enzymes and protected pancreatic tissue; (2) obviously increased the number of in situ terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL)-positive cells and induced apoptosis; (3) markedly inhibited neutrophil infiltration to the impaired pancreas and reduced the inflammatory reaction; (4) notably enhanced the activities of antioxidant enzymes and decreased the nitric oxide synthase levels; (5) significantly reduced the levels of triglycerides, total cholesterol and low-density lipoprotein and increased high-density lipoprotein; and (6) significantly up-regulated peroxisome proliferator-activated receptor-γ (PPARγ) and down-regulated nuclear factor-kappa B (NF-κB). In summary, these results demonstrated that YCHT attenuated SAP progress by inducing apoptosis, repressing inflammation, alleviating oxidative stress and regulating lipid metabolism partially via regulation of the NF-κB/PPARγ signal pathway.

NF-κB in acute pancreatitis: Mechanisms and therapeutic potential

The incidence of acute pancreatitis (AP) is increasing globally and mortality could be high among patients with organ failure and infected necrosis. The predominant factors responsible for the morbidity and mortality of AP are systemic inflammatory response syndrome and multiorgan dysfunction. Even though preclinical studies have shown antisecretory agents (somatostatin), antioxidants (S-adenosyl methionine [SAM], selenium), protease inhibitors, platelet activating factor inhibitor (Lexipafant), and anti-inflammatory immunomodulators (eg. prostaglandin E, indomethacin) to benefit AP in terms of reducing the severity and/or mortality, most of these agents have shown heterogeneous results in clinical studies. Several years of experimental studies have implicated nuclear factor-kappa B (NF-κB) activation as an early and central event in the progression of inflammation in AP. In this manuscript, we review the literature on the role of NF-κB in the pathogenesis of AP, its early intraacinar activation, and how it results in progression of the disease. We also discuss why anti-protease, antisecretory, and anti-inflammatory agents are unlikely to be effective in clinical acute pancreatitis. NF-κB, being a central molecule that links the initial acinar injury to systemic inflammation and perpetuate the inflammation, we propose that more studies be focussed towards targeted inhibition of NF-κB activity. Direct NF-κB inhibition strategies have already been attempted in patients with various cancers. So far, peroxisome proliferator activator receptor gamma (PPAR-γ) ligand, pyrrolidine dithiocarbamate (PDTC), proteasome inhibitor and calpain I inhibitor have been shown to have direct inhibitory effects on NF-κB activation in experimental AP.

Effects of Ranolazine on Astrocytes and Neurons in Primary Culture

Ranolazine (Rn) is an antianginal agent used for the treatment of chronic angina pectoris when angina is not adequately controlled by other drugs. Rn also acts in the central nervous system and it has been proposed for the treatment of pain and epileptic disorders. Under the hypothesis that ranolazine could act as a neuroprotective drug, we studied its effects on astrocytes and neurons in primary culture. We incubated rat astrocytes and neurons in primary cultures for 24 hours with Rn (10-7, 10-6 and 10-5 M). Cell viability and proliferation were measured using trypan blue exclusion assay, MTT conversion assay and LDH release assay. Apoptosis was determined by Caspase 3 activity assay. The effects of Rn on pro-inflammatory mediators IL-β and TNF-α was determined by ELISA technique, and protein expression levels of Smac/Diablo, PPAR-γ, Mn-SOD and Cu/Zn-SOD by western blot technique. In cultured astrocytes, Rn significantly increased cell viability and proliferation at any concentration tested, and decreased LDH leakage, Smac/Diablo expression and Caspase 3 activity indicating less cell death. Rn also increased anti-inflammatory PPAR-γ protein expression and reduced pro-inflammatory proteins IL-1 β and TNFα levels. Furthermore, antioxidant proteins Cu/Zn-SOD and Mn-SOD significantly increased after Rn addition in cultured astrocytes. Conversely, Rn did not exert any effect on cultured neurons. In conclusion, Rn could act as a neuroprotective drug in the central nervous system by promoting astrocyte viability, preventing necrosis and apoptosis, inhibiting inflammatory phenomena and inducing anti-inflammatory and antioxidant agents.

Translational Insights Into Peroxisome Proliferator-Activated Receptors in Experimental Acute Pancreatitis

Acute pancreatitis (AP) is an inflammatory disorder of the exocrine pancreas frequently associated with metabolic causes, contributing factors, or consequences, including hypertriglyceridemia, obesity, and disorders of intermediary metabolism, respectively. To date, there is no specific therapy for this disease. Future optimal therapy should correct both inflammatory and metabolic components of the disease. Peroxisome proliferator-activated receptors (PPARs) are lipid-sensing nuclear receptors that control inflammatory and metabolic pathways via ligand-dependent and ligand-independent mechanisms. There are 3 known subtypes, PPAR-α, PPAR-β/δ, and PPAR-γ, which are differentially expressed in various tissues. The PPARs interact closely with other transcription factors such as nuclear factor κB and signal tranducers and activators of transcription that have pivotal roles in the pathobiology of AP. In this comprehensive review, we summarize the role of PPARs in AP, highlighting important in vitro and in vivo experimental findings. Finally, we propose future research directions as well as potential translational use of PPAR agonists in the treatment of AP.

Apoptotic Mechanisms of Peroxisome Proliferator-Activated Receptor-γ Activation in Acinar Cells During Acute Pancreatitis

OBJECTIVE

The objective of this study was to determine the mechanism by which activation of peroxisome proliferator-activated receptor-γ promotes apoptosis of acinar cells in pancreatitis.

METHODS

AR42j cells pretreated with the peroxisome proliferator-activated receptor-γ agonist pioglitazone were activated by cerulein as an in vitro model of acute pancreatitis. Inflammatory cytokines and amylase were detected by enzyme-linked immunosorbent assay. Cell viability was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Cell apoptosis was measured by flow cytometry and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling staining. Activity of caspases was determined. Bax and Bcl-2 levels were assayed by Western blot.

RESULTS

Cytokines, amylase, and cellular proliferation decreased in pioglitazone-pretreated cells. Pioglitazone increased the activity of caspases 3, 8, and 9 in cerulein-activated AR42j cells as well as in the pancreas of rats 3 hours after induction of severe acute pancreatitis. Acinar cell apoptosis was induced by reducing the mitochondrial membrane potential in the pioglitazone group. Pioglitazone increased expression of proapoptotic Bax proteins and decreased antiapoptotic Bcl-2 in cerulein-induced AR42j cells and decreased Bcl-2 levels in pancreatic tissue of severe acute pancreatitis rats 1 and 3 hours after induction.

CONCLUSION

Pioglitazone may promote apoptosis of acinar cells through both intrinsic and extrinsic apoptotic pathways in acute pancreatitis.

Orange peel extract, containing high levels of polymethoxyflavonoid, suppressed UVB-induced COX-2 expression and PGE2 production in HaCaT cells through PPAR-γ activation

Ultraviolet light (UV) induces an inflammatory response in the skin by cyclooxygenase (COX)-2 expression and prostaglandin (PG) E2 production. Citrus peel has been used as a natural medicine. It contains polymethoxyflavonoids (PMFs) as a major ingredient, which have anti-inflammatory activity. We obtained orange peel extract containing high levels of PMFs. The extract suppressed UVB-induced COX-2 expression and PGE2 production in HaCaT cells. Furthermore, it was found that this extract acted as a peroxisome proliferator-activated receptor (PPAR)-γ agonist. The suppression of UVB-induced COX-2 expression by this extract was inhibited by GW 9662 and T0070907, which are both PPAR-γ antagonists. It is therefore suggested that orange peel extract, containing high levels of PMFs, suppresses UVB-induced COX-2 expression and PGE2 production through PPAR-γ. Hence, these extracts could provide useful protection against or alleviation of UV damage.

Pioglitazone restores IGFBP-3 levels through DNA PK in retinal endothelial cells cultured in hyperglycemic conditions

PURPOSE

Previously, we reported that pioglitazone prevented insulin resistance and cell death in type 2 diabetic retina by reducing TNFα and suppressor of cytokine signaling 3 (SOCS3) levels. Numerous reports suggest prominent vasoprotective effects of insulin growth factor binding protein-3 (IGFBP-3) in diabetic retinopathy. We hypothesized that pioglitazone protects against retinal cell apoptosis by regulating IGFBP-3 levels, in addition to reducing TNFα. The current study explored potential IGFBP-3 regulatory pathways by pioglitazone in retinal endothelial cells cultured in high glucose.

METHODS

Primary human retinal endothelial cells (REC) were grown in normal (5 mM) and high glucose (25 mM) and treated with pioglitazone for 24 hours. Cell lysates were processed for Western blotting and ELISA analysis to evaluate IGFBP-3, TNFα, and cleaved caspase 3 protein levels.

RESULTS

Our results show that treatment with pioglitazone restored the high glucose-induced decrease in IGFBP-3 levels. This regulation was independent of TNFα actions, as reducing TNFα levels with siRNA did not prevent pioglitazone from increasing IGFBP-3 levels. Pioglitazone required protein kinase A (PKA) and DNA-dependent protein kinase (DNA PK) activity to regulate IGFBP-3, as specific inhibitors for each protein prevented pioglitazone-mediated normalization of IGFBP-3 in high glucose. Insulin growth factor binding protein-3 activity was increased and apoptosis decreased by pioglitazone, which was eliminated when serine site 156 of IGFBP-3 was mutated suggesting a key role of this phosphorylation site in pioglitazone actions.

CONCLUSIONS

Our findings suggest that pioglitazone mediates regulation of IGFBP-3 via activation of PKA/DNA PK pathway in hyperglycemic retinal endothelial cells.

A systematic review of acute pancreatitis as an adverse event of type 2 diabetes drugs: from hard facts to a balanced position

The question whether antidiabetes drugs can cause acute pancreatitis dates back to the 1970s. Recently, old concerns have re-emerged following claims that use of incretins, a new class of drugs for type 2 diabetes, might increase the relative risk of acute pancreatitis up to 30-fold. Given that diabetes is per se a potent risk factor for acute pancreatitis and that drug-related acute pancreatitis is rare and difficult to diagnose, we searched the medical databases for information linking acute pancreatitis and type 2 diabetes drugs. Among the biguanides, both phenformin and metformin (the latter in patients with renal insufficiency) have been cited in case reports as a potential cause of acute pancreatitis. Sulphonylureas, as both entire class and single compound (glibenclamide), have also been found in cohort studies to increase its risk. No direct link was found between pancreatic damage and therapy with metaglinide, acarbose, pramlintide or SGLT-2 inhibitors. In animal models, thiazolinediones have demonstrated proprieties to attenuate pancreatic damage, opening perspectives for their use in treating acute pancreatitis in humans. Several case reports and the US Food and Drug Administration pharmacovigilance database indicate an association between acute pancreatitis and incretins, dipeptidyl peptidase-4 (DPP-4) inhibitors, and GLP-1 receptor agonists. To date, however, a clear-cut odds ratio for this association has been reported in only one of eight pharmacoepidemiological studies. Finally, none of the intervention trials investigating these compounds, including two large randomized controlled trials with cardiovascular endpoints, confirmed the purportedly increased risk of acute pancreatitis with incretin use.

Pioglitazone prevents morphine antinociceptive tolerance via ameliorating neuroinflammation in rat cerebral cortex

BACKGROUND

Opioid induced neuroinflammation is shown to be implicated in opioid analgesic tolerance development. In the present study the effect of pioglitazone on morphine-induced tolerance and neuroinflammation in the cerebral cortex of the rat was investigated.

MATERIALS AND METHODS

Various groups of rats received morphine (10mg/kg; ip) and vehicle (po), or morphine (10mg/kg) and pioglitazone (20 or 40 mg/kg; po) once a day for 17 days. In order to determine the possible involvement of PPAR-γ in the pioglitazone effect, one group of rats received PPAR-γ antagonist, GW-9662 (2mg/kg; sc), and pioglitazone (40 mg/kg) and morphine once daily for 17 days. Nociception was assessed using a tail flick apparatus and the percentage of the maximal possible effect was calculated as well. On 18th day, 2h after the last morphine injection, the cerebral cortex of the animals were harvested and the tissue levels of tumour necrosis factor alpha, interleukin-1beta, interleukin-6, interleukin-10 and nuclear factor-kappa B activity were determined.

RESULTS

Co-administration of pioglitazone (40 mg/kg) with morphine not only attenuated morphine-induced tolerance, but also prevented the up-regulation of pro-inflammatory cytokines (tumour necrosis factor alpha, interleukin-1beta, interleukin-6) and nuclear factor-kappa B activity in the rat cerebral cortex. Moreover, GW-9662 (2mg/kg) administration 30 min before pioglitazone, antagonized the above mentioned pioglitazone-induced effects.

CONCLUSION

It is concluded that oral administration of pioglitazone attenuates morphine-induced tolerance. This effect of pioglitazone may be, at least in part, due to its anti-inflammatory property which suppressed the cortical pro-inflammatory cytokine and inhibited of nuclear factor-kappa B activity.

Pioglitazone inhibits the expression of matrix metalloproteinase-9, a protein involved in diabetes-associated wound healing

Matrix metalloproteinase-9 (MMP-9) is a protein involved in diabetes-associated wound healing. The present study aimed to determine whether pioglitazone, an agonist of peroxisome proliferator-activated receptor‑γ (PPAR-γ), inhibits the expression of MMP-9. HaCaT cells at a density of 6x105 cells/well were seeded into 6-well plates in medium and were cultured for 24 h. The cells were then treated with bovine serum albumin (BSA) only or advanced glycation end‑product (AGE)-BSA (50, 100, 200, 300 or 400 µg/ml), with or without pioglitazone (0.5 or 1 µM). The effects of AGE-BSA on cell viability were determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The levels of MMP-9 secreted into the medium were detected by an enzyme-linked immunosorbent assay. The mRNA and protein levels were analyzed by quantitative polymerase chain reaction (qPCR) and western blot analysis, respectively. AGEs are able to increase the level of MMP-9 mRNA in HaCaT cells and the levels of MMP-9 protein secreted into the medium. Pioglitazone (0.5 or 1 µΜ) significantly inhibited the levels of MMP-9 in the treated HaCaT cells. Pioglitazone (0.5 or 1 µΜ) also suppressed the levels of MMP-9 in the cell culture medium. Pioglitazone at concentrations of 0.5 and 1 µΜ significantly suppressed the levels of MMP-9 mRNA to 20 or 8%, respectively. These results suggest that pioglitazone is able to effectively suppress the expression of MMP-9 via a transcriptional mechanism.

Pioglitazone attenuates the detrimental effects of advanced glycation end-products in the pancreatic beta cell line HIT-T15

Pioglitazone is an anti-diabetic agent that preserves pancreatic beta cell mass and improves their function. Advanced Glycation End-Products (AGEs) are implicated in diabetic complications. We previously demonstrated that exposure of the pancreatic islet cell line HIT-T15 to high concentrations of AGEs significantly decreases cell proliferation and insulin secretion, and affects transcription factors regulating insulin gene transcription. The aim of this work was to investigate the effects of Pioglitazone on the function and viability of HIT-T15 cells cultured with AGEs. HIT-T15 cells were cultured for 5 days in the presence of AGEs alone, or supplemented with 1 μmol/l Pioglitazone. Cell viability, insulin secretion and insulin content, redox balance, expression of the AGE receptor (RAGE), and NF-kB activation were then determined. The results showed that Pioglitazone protected beta cells against AGEs-induced apoptosis and necrosis. Moreover, Pioglitazone restored the redox balance and improved the responsiveness to low glucose concentration. Adding Pioglitazone to the AGEs culture attenuated NF-kB phosphorylation, and prevented AGEs to down-regulate IkBα expression. These findings suggest that Pioglitazone protects beta cells from the dangerous effects of AGEs.

The effects of rosiglitazone on osteoblastic differentiation, osteoclast formation and bone resorption

Rosiglitazone has the potential to activate peroxisome proliferator-activated receptor-γ (PPARγ), which in turn can affect bone formation and resorption. However, the mechanisms by which rosiglitazone regulates osteoclastic orosteoblastic differentiation are not fully understood. This study examines how rosiglitazone affects osteoclast formation, bone resorption and osteoblast differentiation from mouse bone marrow. Rosiglitazone treatment not only inhibited the formation of tartrate-resistant acid phosphatase-positive cells, but also prevented pit formation by bone marrow cells in a dose- and time-dependent manner. Rosiglitazone also suppressed the receptor activator of nuclear factor (NF)-κB ligand (RANKL) receptor(RANK) expression but increased PPARγ2 expression in the cells. In addition, rosiglitazone diminished RANKL induced activation of NF-κB-DNA binding by blocking IκBαphosphorylation. Furthermore, it reduced collagen and osteocalcin levels to nearly zero and prevented mRNA expression of osteoblast-specific proteins including runtrelated transcription factor-2, osteocalcin, and type I collagen.However, mRNA levels of adipocyte-specific marker, aP2, were markedly increased in the cells co-incubated with rosiglitazone. These results suggest that PPARγ activation by rosiglitazone inhibits osteoblast differentiation with increased adipogenesis in bone marrow cells and also may prevent osteoclast formation and bone resorptionin the cells.

15-lipoxygenase-1 exerts its tumor suppressive role by inhibiting nuclear factor-kappa B via activation of PPAR gamma

15-Lipoxygenase-1 (15-LOX-1) is an enzyme of the inflammatory eicosanoid pathway whose expression is known to be lost in colorectal cancer (CRC). We have previously shown that reintroduction of the gene in CRC cell lines slows proliferation and induces apoptosis (Cimen et al. [2009] Cancer Sci 100: 2283-2291). We have hypothesized that 15-LOX-1 may be anti-tumorigenic by the inhibition of the anti-apoptotic inflammatory transcription factor nuclear factor kappa B. We show here that ectopic expression of 15-LOX-1 gene in HCT-116 and HT-29 CRC cell lines inhibited the degradation of inhibitor of kappa B (IκBα), decreased nuclear translocation of p65 and p50, decreased DNA binding in the nucleus and decreased transcriptional activity of Nuclear factor kappa B (NF-κB). As the 15-LOX-1 enzymatic product 13(S)-HODE is known to be a peroxisome proliferator-activated receptor gamma (PPARγ) agonist, and NF-κB can be inhibited by PPARγ, we examined whether activation of PPARγ was necessary for the abrogation of NF-κB activity. Our data show that the inhibition of both early and late stages of NF-κB activation could rescued by the PPARγ antagonist GW9662 indicating that the inhibition was most likely mediated via PPARγ.

Lycopene inhibits IL-6 expression in cerulein-stimulated pancreatic acinar cells

Reactive oxygen species (ROS) are known to be involved in the pathogenesis of acute and chronic pancreatitis. The cholecystokinin (CCK) analog cerulein causes pathophysiological, morphological, and biochemical events similar to those observed in human acute pancreatitis. The oxidant-sensitive transcription factor NF-κB plays a critical role in the development of cerulein pancreatitis by regulating the expression of pro-inflammatory cytokines in the pancreas. Lycopene has an anti-oxidant effect in various cells. In the present study, we investigated whether cerulein induces NF-κB activation and IL-6 expression in pancreatic acinar cells and whether lycopene inhibits these events. NF-κB-DNA-binding activity was determined by electrophoretic mobility shift assay, and mRNA expression was analyzed by reverse transcription-polymerase chain reaction (RT-PCR) and real-time RT-PCR analyses. The IL-6 concentration in the medium was determined by enzyme-linked immunosorbent assay. Our results showed that cerulein induced IL-6 expression in a time-dependent manner. NF-κB-DNA-binding activity and intracellular levels of ROS in pancreatic acinar cells were increased by cerulein. Lycopene inhibited the cerulein-induced increase in intracellular ROS, NF-κB activation, and IL-6 expression in pancreatic acinar cells in a dose-dependent manner. In conclusion, lycopene may be beneficial in the prevention and/or treatment of acute pancreatitis by inhibiting the activation of NF-κB and the expression of inflammatory cytokines through reduction in intracellular levels of ROS in pancreatic acinar cells.

Opposite action of peroxisome proliferator-activated receptor-gamma in regulating renal inflammation: functional switch by its ligand

Peroxisome proliferator-activated receptor-γ (PPARγ) agonists, a new class of antidiabetic agents, have been shown to possess antiinflammatory activity. In this study, we investigated the molecular mechanism by which PPARγ agonists inhibit proinflammatory cytokine expression in rat glomerular mesangial cells. Both natural and synthetic PPARγ agonists potently inhibited RANTES (regulated upon activation, normal T cell expressed and secreted) and monocyte chemoattractant protein-1 expression induced by TNF-α in mesangial cells, which was dependent on NF-κB signaling. However, PPARγ agonists had little effect on TNF-α-triggered IκBα phosphorylation and its subsequent degradation, p65 phosphorylation, and nuclear translocation. In the absence of PPARγ ligand, TNF-α induced a physical interaction between nuclear p65 and PPARγ, as demonstrated by co-immunoprecipitation. Such an interaction was mediated by the C-terminal region of p65. Activation of PPARγ by its agonist prevented PPARγ·p65 complex formation. Chromatin immunoprecipitation assay revealed that TNF-α induced p65 binding to the cis-acting κB elements in rat RANTES promoter, whereas disruption of PPARγ·p65 by its agonist blocked p65 interaction with its cognate κB sites. Knockdown of PPARγ via siRNA strategy completely abolished TNF-α-mediated p65 binding to κB sites and negated RANTES induction, suggesting that unliganded PPARγ is obligatory for NF-κB signaling. Consistently, overexpression of PPARγ in the absence of its ligand sensitized mesangial cells to TNF-α stimulation. These results uncover a paradoxical action of the unliganded and ligand-activated PPARγ in regulating NF-κB signaling and demonstrate PPARγ ligand as a molecular switch that controls its ability to modulate inflammatory responses in opposite directions.

Effect of pioglitazone on expression of intercellular adhesion molecule-1 in pulmonary tissues of rats with severe acute pancreatitis

AIM: To investigate the expression changes of pulmonary intercellular adhesion molecule-1 (ICAM-1) after pioglitazone treatment in rats with severe acute pancreatitis (SAP).

METHODS: A total of 54 Sprague Dawley rats were randomly and divided into 3 groups, named group A, C and T (n = 18). Group A and C served as SAP model group and sham operation group, respectively. Rats in group T were treated with pioglitazone, an agonist of peroxisome proliferator activated receptor. The modified Li Qing-hua's method was used to reproduce SAP models. Histopathological changes of pulmonary tissues were examined by microscopy. The activity of myeloperoxidase (MPO) in pulmonary tissues was measured. The expression of pulmonary ICAM-1 was determined by immunohistochemical staining (ABC).

RESULTS: The histological examination revealed intensive inflammatory response in pulmonary tissues after SAP model was induced, but inflammatory response was significantly alleviated in group T. The activity of MPO (6 h: 5.12 ± 0.71 vs 6.03 ± 0.63, P < 0.05; 12 h: 5.20 ± 0.66 vs 8.05 ± 0.62, P < 0.01) in the lung tissues were significantly decreased. After modeling, the expression of ICAM-1 was persistently increased from the 3^rd hour on. In group A, the expression of ICAM-1 was 0.82 ± 0.23, 1.03 ± 0.31 and 1.40 ± 0.58 at the 3^rd, 6^th, and 12^th hour, respectively, and there was significant difference between those at the 12th and 3rd hour (P < 0.05). In group T, ICAM-1 expression was 0.62 ± 0.18, 0.75 ± 0.27 and 0.78 ± 0.31 at the 3^rd, 6^th, and 12th hour, respectively, and there was marked difference at the 12th hour between group A and group T (P < 0.05). ICAM-1 expression was weakly positive in group C, and faded away as time went by.

CONCLUSION: The severity of pancreatitis and degree of lung injury could be predicted by detection of ICAM-1 expression and pioglitazone inhibits the expression of ICAM-1 in SAP.