Role of PKC-delta on substance P-induced chemokine synthesis in pancreatic acinar cells

Hydrogen Sulfide and its Interaction with Other Players in Inflammation

Hydrogen sulfide (H₂S) plays a vital role in human physiology and in the pathophysiology of several diseases. In addition, a substantial role of H₂S in inflammation has emerged. This chapter will discuss the involvement of H₂S in various inflammatory diseases. Furthermore, the contribution of reactive oxygen species (ROS), adhesion molecules, and leukocyte recruitment in H₂S-mediated inflammation will be discussed. The interrelationship of H₂S with other gasotransmitters in inflammation will also be examined. There is mixed literature on the contribution of H₂S to inflammation due to studies reporting both pro- and anti-inflammatory actions. These apparent discrepancies in the literature could be resolved with further studies.

Intracellular emetic signaling cascades by which the selective neurokinin type 1 receptor (NK1R) agonist GR73632 evokes vomiting in the least shrew (Cryptotis parva)

To characterize mechanisms involved in neurokinin type 1 receptor (NK₁R)-mediated emesis, we investigated the brainstem emetic signaling pathways following treating least shrews with the selective NK₁R agonist GR73632. In addition to episodes of vomiting over a 30-min observation period, a significant increase in substance P-immunoreactivity in the emetic brainstem dorsal motor nucleus of the vagus (DMNX) occurred at 15 min post an intraperitoneal (i.p.) injection GR73632 (5 mg/kg). In addition, time-dependent upregulation of phosphorylation of several emesis -associated protein kinases occurred in the brainstem. In fact, Western blots demonstrated significant phosphorylations of Ca²⁺/calmodulin kinase IIα (CaMKIIα), extracellular signal-regulated protein kinase1/2 (ERK1/2), protein kinase B (Akt) as well as α and βII isoforms of protein kinase C (PKCα/βII). Moreover, enhanced phospho-ERK1/2 immunoreactivity was also observed in both brainstem slices containing the dorsal vagal complex emetic nuclei as well as in jejunal sections from the shrew small intestine. Furthermore, our behavioral findings demonstrated that the following agents suppressed vomiting evoked by GR73632 in a dose-dependent manner: i) the NK₁R antagonist netupitant (i.p.); ii) the L-type Ca²⁺ channel (LTCC) antagonist nifedipine (subcutaneous, s.c.); iii) the inositol trisphosphate receptor (IP₃R) antagonist 2-APB (i.p.); iv) store-operated Ca²⁺ entry inhibitors YM-58483 and MRS-1845, (i.p.); v) the ERK1/2 pathway inhibitor U0126 (i.p.); vi) the PKC inhibitor GF109203X (i.p.); and vii) the inhibitor of phosphatidylinositol 3-kinase (PI3K)-Akt pathway LY294002 (i.p.). Moreover, NK₁R, LTCC, and IP₃R are required for GR73632-evoked CaMKIIα, ERK1/2, Akt and PKCα/βII phosphorylation. In addition, evoked ERK1/2 phosphorylation was sensitive to inhibitors of PKC and PI3K. These findings indicate that the LTCC/IP₃R-dependent PI3K/PKCα/βII-ERK1/2 signaling pathways are involved in NK₁R-mediated vomiting.

Ginsenoside Re protects methamphetamine-induced dopaminergic neurotoxicity in mice via upregulation of dynorphin-mediated κ-opioid receptor and downregulation of substance P-mediated neurokinin 1 receptor

BACKGROUND

We previously reported that ginsenoside Re (GRe) attenuated against methamphetamine (MA)-induced neurotoxicity via anti-inflammatory and antioxidant potentials. We also demonstrated that dynorphin possesses anti-inflammatory and antioxidant potentials against dopaminergic loss, and that balance between dynorphin and substance P is important for dopaminergic neuroprotection. Thus, we examined whether GRe positively affects interactive modulation between dynorphin and substance P against MA neurotoxicity in mice.

METHODS

We examined changes in dynorphin peptide level, prodynorphin mRNA, and substance P mRNA, substance P-immunoreactivity, homeostasis in enzymatic antioxidant system, oxidative parameter, microglial activation, and pro-apoptotic parameter after a neurotoxic dose of MA to clarify the effects of GRe, prodynorphin knockout, pharmacological inhibition of κ-opioid receptor (i.e., nor-binaltorphimine), or neurokinin 1 (NK1) receptor (i.e., L-733,060) against MA insult in mice.

RESULTS

GRe attenuated MA-induced decreases in dynorphin level, prodynorphin mRNA expression in the striatum of wild-type (WT) mice. Prodynorphin knockout potentiated MA-induced dopaminergic toxicity in mice. The imbalance of enzymatic antioxidant system, oxidative burdens, microgliosis, and pro-apoptotic changes led to the dopaminergic neurotoxicity. Neuroprotective effects of GRe were more pronounced in prodynorphin knockout than in WT mice. Nor-binaltorphimine, a κ-opioid receptor antagonist, counteracted against protective effects of GRe. In addition, we found that GRe significantly attenuated MA-induced increases in substance P-immunoreactivity and substance P mRNA expression in the substantia nigra. These increases were more evident in prodynorphin knockout than in WT mice. Although, we observed that substance P-immunoreactivity was co-localized in NeuN-immunreactive neurons, GFAP-immunoreactive astrocytes, and Iba-1-immunoreactive microglia. NK1 receptor antagonist L-733,060 or GRe selectively inhibited microgliosis induced by MA. Furthermore, L-733,060 did not show any additive effects against GRe-mediated protective activity (i.e., antioxidant, antimicroglial, and antiapoptotic effects), indicating that NK1 receptor is one of the molecular targets of GRe.

CONCLUSIONS

Our results suggest that GRe protects MA-induced dopaminergic neurotoxicity via upregulatgion of dynorphin-mediated κ-opioid receptor and downregulation of substance P-mediated NK1 R.

A Mini-Review on the Effect of Docosahexaenoic Acid (DHA) on Cerulein-Induced and Hypertriglyceridemic Acute Pancreatitis

Acute pancreatitis refers to the sudden inflammation of the pancreas. It is associated with premature activation and release of digestive enzymes into the pancreatic interstitium and systemic circulation, resulting in pancreatic tissue autodigestion and multiple organ dysfunction, as well as with increased cytokine production, ultimately leading to deleterious local and systemic effects. Although mechanisms involved in pathogenesis of acute pancreatitis have not been completely elucidated, oxidative stress is regarded as a major risk factor. In human acute pancreatitis, lipid peroxide levels in pancreatic tissues increase. Docosahexaenoic acid (DHA), an omega-3 polyunsaturated fatty acid (C22:6n-3), exerts anti-inflammatory and antioxidant effects on various cells. Previous studies have shown that DHA activates peroxisome proliferator-activated receptor-γ and induces catalase, which inhibits oxidative stress-mediated inflammatory signaling required for cytokine expression in experimental acute pancreatitis using cerulein. Cerulein, a cholecystokinin analog, induces intra-acinar activation of trypsinogen in the pancreas, which results in human acute pancreatitis-like symptoms. Therefore, DHA supplementation may be beneficial for preventing or inhibiting acute pancreatitis development. Since DHA reduces serum triglyceride levels, addition of DHA to lipid-lowering drugs like statins has been investigated to reduce hypertriglyceridemic acute pancreatitis. However, high DHA concentrations increase cytosolic Ca²⁺, which activates protein kinase C and may induce hyperlipidemic acute pancreatitis. In this review, effect of DHA on cerulein-induced and hypertriglyceridemic acute pancreatitis has been discussed. The relation of high concentration of DHA to hyperlipidemic acute pancreatitis has been included.

Long intergenic noncoding RNA p21 mediates oxidized LDL‑induced apoptosis and expression of LOX‑1 in human coronary artery endothelial cells

Atherosclerosis is the most common pathological cause of cardiovascular diseases, and endothelial dysfunction has a vital role. It has been suggested that inhibiting endothelial cell apoptosis induced by oxidized low‑density lipoprotein (ox‑LDL), an essential atherosclerotic factor, is a potential novel therapeutic strategy against atherosclerosis. Previous studies have revealed that endothelial lectin‑like ox‑LDL receptor‑1 (LOX‑1) and long intergenic noncoding RNA p21 (lincRNA‑p21) may serve as therapeutic targets for atherosclerosis and associated cardiovascular disorders. The present study investigated the role of lincRNA‑p21 in oxLDL‑induced apoptosis and expression of LOX‑1 in human coronary artery endothelial cells (HCAECs). Primary HCAECs were treated with ox‑LDL (30, 60 or 90 µg/ml) for 24 or 48 h, and the expression of lincRNA‑p21, LOX‑1 and cell apoptosis rate were measured. Ox‑LDL dose‑ and time‑dependently induced the expression of lincRNA‑p21 and LOX‑1 and apoptosis in HCAECs. Lentiviral overexpression of lincRNA‑p21 markedly increased oxLDL‑induced apoptosis and the expression of LOX‑1 in HCAECs. Additionally, the effect was largely blocked by selective protein kinase C (PKC) inhibitor, rottlerin. However, lentiviral knockdown of lincRNA‑p21 markedly decreased oxLDL‑induced apoptosis and the expression of LOX‑1. In addition, overexpression and knockdown of lincRNA‑p21 markedly increased and decreased oxLDL‑induced PKCδ activity/phosphorylation, respectively. In conclusion, to the best of our knowledge, the present study provides the first evidence indicating that lincRNA‑p21 is a major mediator of oxLDL‑induced apoptosis and expression of LOX‑1 in human vascular endothelial cells, and acts via activation of PKCδ. These results provide insights into the role of lincRNA‑p21 in the pathogenesis of atherosclerosis.

Src kinases play a novel dual role in acute pancreatitis affecting severity but no role in stimulated enzyme secretion

In pancreatic acinar cells, the Src family of kinases (SFK) is involved in the activation of several signaling cascades that are implicated in mediating cellular processes (growth, cytoskeletal changes, apoptosis). However, the role of SFKs in various physiological responses such as enzyme secretion or in pathophysiological processes such as acute pancreatitis is either controversial, unknown, or incompletely understood. To address this, in this study, we investigated the role/mechanisms of SFKs in acute pancreatitis and enzyme release. Enzyme secretion was studied in rat dispersed pancreatic acini, in vitro acute-pancreatitis-like changes induced by supramaximal COOH-terminal octapeptide of cholecystokinin (CCK). SFK involvement assessed using the chemical SFK inhibitor (PP2) with its inactive control, 4-amino-7-phenylpyrazol[3,4-d]pyrimidine (PP3), under experimental conditions, markedly inhibiting SFK activation. In CCK-stimulated pancreatic acinar cells, activation occurred of trypsinogen, various MAP kinases (p42/44, JNK), transcription factors (signal transducer and activator of transcription-3, nuclear factor-κB, activator protein-1), caspases (3, 8, and 9) inducing apoptosis, LDH release reflective of necrosis, and various chemokines secreted (monocyte chemotactic protein-1, macrophage inflammatory protein-1α, regulated on activation, normal T cell expressed and secreted). All were inhibited by PP2, not by PP3, except caspase activation leading to apoptosis, which was increased, and trypsin activation, which was unaffected, as was CCK-induced amylase release. These results demonstrate SFK activation is playing a dual role in acute pancreatitis, inhibiting apoptosis and promoting necrosis as well as chemokine/cytokine release inducing inflammation, leading to more severe disease, as well as not affecting secretion. Thus, our studies indicate that SFK is a key mediator of inflammation and pancreatic acinar cell death in acute pancreatitis, suggesting it could be a potential therapeutic target in acute pancreatitis.

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.

Substance P enhances tissue factor release from granulocyte-macrophage colony-stimulating factor-dependent macrophages via the p22phox/β-arrestin 2/Rho A signaling pathway

Granulocyte-macrophage colony stimulating factor (GM-CSF) induces procoagulant activity of macrophages. Tissue factor (TF) is a membrane-bound glycoprotein and substance P (SP) is a pro-inflammatory neuropeptide involved in the formation of membrane blebs. This study investigated the role of SP in TF release by GM-CSF-dependent macrophages. SP significantly decreased TF levels in whole-cell lysates of GM-CSF-dependent macrophages. TF was detected in the culture supernatant by enzyme-linked immunosorbent assay after stimulation of macrophages by SP. Aprepitant (an SP/neurokinin 1 receptor antagonist) reduced TF release from macrophages stimulated with SP. Pretreatment of macrophages with a radical scavenger(pyrrolidinedithiocarbamate) also limited the decrease of TF in whole-cell lysates after stimulation with SP. A protein kinase C inhibitor (rottlerin) partially blocked this macrophage response to SP, while it was significantly inhibited by a ROCK inhibitor (Y-27632) or a dynamin inhibitor (dinasore). An Akt inhibitor (perifosine) also partially blocked this response. Furthermore, siRNA targeting p22phox, β-arrestin 2, or Rho A, blunted the release of TF from macrophages stimulated with SP. In other experiments, visceral adipocytes derived from cryopreserved preadipocytes were found to produce SP. In conclusion, SP enhances the release of TF from macrophages via the p22phox/β-arrestin 2/Rho A signaling pathway.

Distinctive roles of unsaturated and saturated fatty acids in hyperlipidemic pancreatitis

AIM: To investigate how the saturated and unsaturated fatty acid composition influences the susceptibility of developing acute pancreatitis.

METHODS: Primary pancreatic acinar cells were treated with low and high concentrations of different saturated and unsaturated fatty acids, and changes in the cytosolic Ca²⁺ signal and the expression of protein kinase C (PKC) were measured after treatment.

RESULTS: Unsaturated fatty acids at high concentrations, including oleic acid, linoleic acid, palmitoleic acid, docosahexaenoic acid, and arachidonic acid, induced a persistent rise in cytosolic Ca²⁺ concentrations in acinar cells. Unsaturated fatty acids at low concentrations and saturated fatty acids, including palmitic acid, stearic acid, and triglycerides, at low and high concentrations were unable to induce a rise in Ca²⁺ concentrations in acinar cells. Unsaturated fatty acids at high concentrations but not saturated fatty acids induced intra-acinar cell trypsin activation and cell damage and increased PKC expression.

CONCLUSION: At sufficiently high concentrations, unsaturated fatty acids were able to induce acinar cells injury and promote the development of pancreatitis. Unsaturated fatty acids may play a distinctive role in the pathogenesis of pancreatitis through the activation of PKC family members.

Hypertriglyceridemia-induced pancreatitis and risk of persistent systemic inflammatory response syndrome

BACKGROUND

The mechanisms responsible for the development of acute pancreatitis (AP) and its complications are not fully understood.

AIM

To assess the role of clinical and host molecular factors for the development and outcome of persistent systemic inflammatory response syndrome (SIRS) in patients with AP.

METHODS

We included 191 patients with AP in the study. The considered variables were demographic characteristics, prognosis and outcome, etiology, laboratory findings and complications. Interleukin (IL) 10 (-1082 G/A, -592 C/A), TNFA-308 (G/A) and ILB-31 (C/T) polymorphisms were determined by pyrosequencing. An amplification refractory mutation system-polymerase chain reaction method was used to genotype the IL8-251 (A/T) polymorphism.

RESULTS

Demographic characteristics were not statistically significant risk factors for the acquisition of persistent SIRS in patients with AP. Patients with hypertriglyceridemia were more likely to develop persistent SIRS (P < 0.05). No association with the TNFA, ILB, IL8-251 (A/T) and IL10 single-nucleotide polymorphisms was detected from the allele, genotype or haplotype frequencies.

CONCLUSIONS

Patients with hypertriglyceridemia-induced AP were more likely to develop persistent SIRS.

Regulated norepinephrine transporter interaction with the neurokinin-1 receptor establishes transporter subcellular localization

Neurokinin-1 receptor (NK1R) mediates down-regulation of human norepinephrine (NE) transporter (hNET) via protein kinase C (PKC). However, native NET regulation by NK1R and the mechanism by which NK1R targets NET among other potential effectors are unknown. Effect of NK1R activation on native NET regulation and NET/NK1R interaction were studied using rat brain synaptosomes expressing native NET and NK1R as well as human placental trophoblast (HTR) cells coexpressing WT-hNET or NK1R/PKC-resistant hNET-T258A,S259A double mutant (NET-DM) and hNK1R. The selective NK1R agonist, GR73632, and Substance-P (SP) inhibited NE transport and reduced plasma membrane expression of NET and NK1R. Pretreatment with the NK1R antagonist, EMEND (aprepitant) prevented these NK1R-mediated effects. Immunoprecipitation experiments showed that NET forms stable complexes with NK1R. In HTR cells, combined biotinylation and immunoprecipitation studies revealed plasma membrane localization of NET·NK1R complexes. Receptor activation resulted in the internalization of NET·NK1R complexes. Lipid raft and immunoprecipitation analyses revealed the presence of NET·NK1R complexes exclusively in non-raft membrane fractions under basal/unstimulated conditions. However, NK1R activation led to translocation of NET·NK1R complexes to raft-rich membrane fractions. Importantly, PKCα was found in association with raft-localized NET following SP treatment. Similar to WT-NET, PKC-resistant NET-DM was found in association with NK1R exclusively in non-raft fractions. However, SP treatment failed to translocate NET-DM·NK1R complexes from non-raft fractions to raft fractions. Collectively, these results suggest that NK1R forms physical complexes with NET and that the receptor-mediated Thr(258) + Ser(259) motif-dependent translocation of NET·NK1R complexes into raft-rich microdomains facilitates NET/NK1R interaction with PKCα to coordinate spatially restricted NET regulation.

Activation of neurokinin-1 receptors up-regulates substance P and neurokinin-1 receptor expression in murine pancreatic acinar cells

Acute pancreatitis (AP) has been associated with an up-regulation of substance P (SP) and neurokinin-1 receptor (NK1R) in the pancreas. Increased SP-NK1R interaction was suggested to be pro-inflammatory during AP. Previously, we showed that caerulein treatment increased SP/NK1R expression in mouse pancreatic acinar cells, but the effect of SP treatment was not evaluated. Pancreatic acinar cells were obtained from pancreas of male swiss mice (25–30 g). We measured mRNA expression of preprotachykinin-A (PPTA) and NK1R following treatment of SP (10⁻⁶M). SP treatment increased PPTA and NK1R expression in isolated pancreatic acinar cells, which was abolished by pretreatment of a selective NK1R antagonist, CP96,345. SP also time dependently increased protein expression of NK1R. Treatment of cells with a specific NK1R agonist, GR73,632, up-regulated SP protein levels in the cells. Using previously established concentrations, pre-treatment of pancreatic acinar cells with Gö6976 (10 nM), rottlerin (5 μM), PD98059 (30 μM), SP600125 (30 μM) or Bay11-7082 (30 μM) significantly inhibited up-regulation of SP and NK1R. These observations suggested that the PKC-ERK/JNK-NF-κB pathway is necessary for the modulation of expression levels. In comparison, pre-treatment of CP96,345 reversed gene expression in SP-induced cells, but not in caerulein-treated cells. Overall, the findings in this study suggested a possible auto-regulatory mechanism of SP/NK1R expression in mouse pancreatic acinar cells, via activation of NK1R. Elevated SP levels during AP might increase the occurrence of a positive feedback loop that contributes to abnormally high expression of SP and NK1R.

Role of hydrogen sulfide in the pathology of inflammation

Hydrogen sulfide (H2S) is a well-known toxic gas that is synthesized in the human body from the amino acids cystathionine, homocysteine, and cysteine by the action of at least two distinct enzymes: cystathionine-γ-lyase and cystathionine-β-synthase. In the past few years, H2S has emerged as a novel and increasingly important biological mediator. Imbalances in H2S have also been shown to be associated with various disease conditions. However, defining the precise pathophysiology of H2S is proving to be a complex challenge. Recent research in our laboratory has shown H2S as a novel mediator of inflammation and work in several groups worldwide is currently focused on determining the role of H2S in inflammation. H2S has been implicated in different inflammatory conditions, such as acute pancreatitis, sepsis, joint inflammation, and chronic obstructive pulmonary disease (COPD). Active research on the role of H2S in inflammation will unravel the pathophysiology of its actions in inflammatory conditions and may help develop novel therapeutic approaches for several, as yet incurable, disease conditions.

Role of protein kinase C in caerulein induced expression of substance P and neurokinin-1-receptors in murine pancreatic acinar cells

Substance P (SP) is involved in the pathophysiology of acute pancreatitis (AP) via binding to its high-affinity receptor, neurokinin-1-receptor (NK1R). An up-regulation of SP and NK1R expression was observed in experimental AP and in caerulein-stimulated pancreatic acinar cells. However, the mechanisms that lead to this up-regulation are not fully understood. In this study, we showed the role of protein kinase C (PKC) in caerulein-induced SP and NK1R production in isolated mouse pancreatic acinar cells. Caerulein (10(-7) M) stimulation rapidly activated the conventional PKC-α and novel PKC-δ as observed by the phosphorylation of these molecules. Pre-treatment of pancreatic acinar cells with Gö6976 (1-10 nM) and rottlerin (1-10 μM) inhibited PKC-α and PKC-δ phosphorylation, respectively, but not the other way round. At these concentrations used, PKC-α and PKC-δ inhibition reversed the caerulein-induced up-regulation of SP and NK1R, indicating an important role of PKCs in the modulation of SP and NK1R expression. Further experiments looking into signalling mechanisms showed that treatment of pancreatic acinar cells with both Gö6976 and rottlerin inhibited the activation of extracellular signal-regulated kinase 1/2 (ERK1/2) and c-Jun N-terminal kinase (JNK). Inhibition of PKC-α or PKC-δ also affected caerulein-induced transcription factor activation, as represented by nuclear factor-κB and AP-1 DNA-binding activity. The findings in this study suggested that PKC is upstream of the mitogen-activated protein kinases and transcription factors, which then lead to the up-regulation of SP/NK1R expression in caerulein-treated mouse pancreatic acinar cells.

The role of neutral endopeptidase in caerulein-induced acute pancreatitis

Substance P (SP) is well known to promote inflammation in acute pancreatitis (AP) by interacting with neurokinin-1 receptor. However, mechanisms that terminate SP-mediated responses are unclear. Neutral endopeptidase (NEP) is a cell-surface enzyme that degrades SP in the extracellular fluid. In this study, we examined the expression and the role of NEP in caerulein-induced AP. Male BALB/c mice (20-25 g) subjected to 3-10 hourly injections of caerulein (50 μg/kg) exhibited reduced NEP activity and protein expression in the pancreas and lungs. Additionally, caerulein (10(-7) M) also downregulated NEP activity and mRNA expression in isolated pancreatic acinar cells. The role of NEP in AP was examined in two opposite ways: inhibition of NEP (phosphoramidon [5 mg/kg] or thiorphan [10 mg/kg]) followed by 6 hourly caerulein injections) or supplementation with exogenous NEP (10 hourly caerulein injections, treatment of recombinant mouse NEP [1 mg/kg] during second caerulein injection). Inhibition of NEP raised SP levels and exacerbated inflammatory conditions in mice. Meanwhile, the severity of AP, determined by histological examination, tissue water content, myeloperoxidase activity, and plasma amylase activity, was markedly better in mice that received exogenous NEP treatment. Our results suggest that NEP is anti-inflammatory in caerulein-induced AP. Acute inhibition of NEP contributes to increased SP levels in caerulein-induced AP, which leads to augmented inflammatory responses in the pancreas and associated lung injury.

Oxidative and nitrosative stress in acute pancreatitis. Modulation by pentoxifylline and oxypurinol

Reactive oxygen species are considered mediators of the inflammatory response and tissue damage in acute pancreatitis. We previously found that the combined treatment with oxypurinol - as inhibitor of xanthine oxidase- and pentoxifylline - as inhibitor of TNF-α production-restrained local and systemic inflammatory response and decreased mortality in experimental acute pancreatitis. Our aims were (1) to determine the time-course of glutathione depletion and oxidation in necrotizing pancreatitis in rats and its modulation by oxypurinol and pentoxifylline; (2) to determine whether TNF-α is responsible for glutathione depletion in acute pancreatitis; and (3) to elucidate the role of oxidative stress in the inflammatory cascade in pancreatic AR42J acinar cells. We report here that oxidative stress and nitrosative stress occur in pancreas and lung in acute pancreatitis and the co-treatment with oxypurinol and pentoxifylline prevents oxidative stress in both tissues. Oxypurinol was effective in preventing glutathione oxidation, whereas pentoxifylline abrogated glutathione depletion. This latter effect was independent of TNF-α since glutathione depletion occurred in mice deficient in TNF-α or its receptors after induction of pancreatitis. The beneficial effects of oxypurinol in the inflammatory response may also be ascribed to a partial inhibition of MEK1/2 activity. Pentoxifylline markedly reduced the expression of Icam1 and iNos induced by TNF-α in vitro in AR42J cells. Oxidative stress significantly contributes to the TNF-α-induced up-regulation of Icam and iNos in AR42J cells. These results provide new insights into the mechanism of action of oxypurinol and pentoxifylline as anti-inflammatory agents in acute pancreatitis.

Artemisinin inhibits extracellular matrix metalloproteinase inducer (EMMPRIN) and matrix metalloproteinase-9 expression via a protein kinase Cδ/p38/extracellular signal-regulated kinase pathway in phorbol myristate acetate-induced THP-1 macrophages

1. Overexpression of extracellular matrix metalloproteinase inducer (EMMPRIN) and matrix metalloproteinases (MMPs) by monocytes/macrophages has been proposed to play a significant role in atherosclerotic plaque progression and rupture. The aim of the present study was to explore whether artemisinin, a natural extract from Artemisia annua, could decrease EMMPRIN and MMP-9 expression in phorbol myristate acetate (PMA)-induced macrophages by regulating the protein kinase (PK) Cδ/c-Jun N-terminal kinase (JNK)/p38/extracellular signal-regulated kinase (ERK) pathway. 2. Human monocytic THP-1 cells were pretreated with 20-80 μg/mL artemisinin for 4 h or 1-10 μmol/L rottlerin for 1 h prior to stimulation with PMA (100 nmol/L) for another 48 h. Cells were collected to analyse the induction of EMMPRIN and MMP-9. Upstream pathway analysis using the PKCδ inhibitor rottlerin detected activation of the PKCδ/JNK/p38/ERK pathway. 3. Artemisinin (20-80 μg/mL) significantly inhibited the induction of EMMPRIN and MMP-9 at both the transcriptional and translational levels in a dose-dependent manner in PMA-induced macrophages. In addition, artemisinin (20-80 μg/mL) strongly blocked PKCδ/JNK/p38/ERK MAPK phosphorylation. The PKCδ inhibitor rottlerin (1-10 μmol/L) also significantly inhibited JNK/p38/ERK phosphorylation and decreased EMMPRIN and MMP-9 mRNA and protein expression. 4. The results of the present study suggest that artemisinin inhibits EMMPRIN and MMP-9 expression and activity by suppressing the PKCδ/ERK/p38 cascade in PMA-induced macrophages.

Substance P activates both contractile and inflammatory pathways in lymphatics through the neurokinin receptors NK1R and NK3R

OBJECTIVE

The aim of this study was to elucidate the molecular signaling mechanisms by which substance P (SP) modulates lymphatic muscle contraction and to determine whether SP stimulates both contractile as well as inflammatory pathways in the lymphatics.

METHODS

A rat mesenteric lymphatic muscle cell culture model (RMLMCs) and known specific pharmacological inhibitors were utilized to delineate SP-mediated signaling pathways in lymphatics.

RESULTS

We detected expression of neurokinin receptor 1 (NK1R) and neurokinin receptor 3 (NK3R) in RMLMCs. SP stimulation increased phosphorylation of myosin light chain 20 (MLC₂₀) as well as p38 mitogen associated protein kinase (p38-MAPK) and extracellular signal regulated kinase (ERK1/2) indicating activation of both a contractile and a pro-inflammatory MAPK pathway. Pharmacological inhibition of both NK1R and NK3R significantly affected the downstream SP signaling. We further examined whether there was any crosstalk between the two pathways upon SP stimulation. Inhibition of ERK1/2 decreased levels of p-MLC₂₀ after SP activation, in a PKC dependent manner, indicating a potential crosstalk between these two pathways.

CONCLUSIONS

These data provide the first evidence that SP-mediated crosstalk between pro-inflammatory and contractile signaling mechanisms exists in the lymphatic system and may be an important bridge between lymphatic function modulation and inflammation.

Regulation of acinar cell function in the pancreas

PURPOSE OF REVIEW

This review identifies and puts into context the recent articles which have advanced understanding of the functions of pancreatic acinar cells and the mechanisms by which these functions are regulated.

RECENT FINDINGS

Receptors present on acinar cells, particularly those for cholecystokinin and secretin, have been better characterized as to the molecular nature of the ligand-receptor interaction. Other reports have described the potential regulation of acinar cells by GLP-1 and cannabinoids. Intracellular Ca2+ signaling remains at the center of stimulus secretion coupling and its regulation has been further defined. Recent studies have identified specific channels mediating Ca2+ release from intracellular stores and influx across the plasma membrane. Work downstream of intracellular mediators has focused on molecular mechanisms of exocytosis particularly involving small G proteins, SNARE proteins and chaperone molecules. In addition to secretion, recent studies have further defined the regulation of pancreatic growth both in adaptive regulation to diet and hormones in the regeneration that occurs after pancreatic damage. Lineage tracing has been used to show the contribution of different cell types. The importance of specific amino acids as signaling molecules to activate the mTOR pathway is being elucidated.

SUMMARY

Understanding the mechanisms that regulate pancreatic acinar cell function is contributing to knowledge of normal pancreatic function and alterations in disease.

PKC δ mediates pro-inflammatory responses in a mouse model of caerulein-induced acute pancreatitis

Acute pancreatitis is an inflammatory disorder of the pancreas. Protein kinase C (PKC) δ plays an important role in mediating chemokine production in mouse pancreatic acinar cells. This study aims to investigate the role of PKC δ in the pathogenesis of acute pancreatitis and to explore the mechanisms through which PKC δ mediates pro-inflammatory signaling. Acute pancreatitis was induced in mice by ten hourly intraperitoneal injections of caerulein. PKC δ translocation inhibitor peptide (δV1-1) at a dose of 1.0 mg/kg or Tat (carrier peptide) at a dose of 1.0 mg/kg was administered to mice either 1 h before or 1 h after the first caerulein injection. One hour after the last caerulein injection, the mice were killed and pancreas, lungs, and blood were collected. Prophylactic and therapeutic treatment with δV1-1 attenuated caerulein-induced plasma amylase levels and pancreatic edema. Treatment with δV1-1 decreased myeloperoxidase activity and monocyte chemotactic protein-1 levels in both pancreas and plasma. PKC δ mediated acute pancreatitis by activating pancreatic nuclear factor κB, activator protein-1, and mitogen-activated protein kinases. Moreover, blockade of PKC δ attenuated lung myeloperoxidase activity and edema. Histological examination of pancreatic and lung sections confirmed protection against acute pancreatitis. Treatment with Tat had no protective effect on acute pancreatitis. Blockade of PKC δ represents a promising prophylactic and/or therapeutic tool for the treatment of acute pancreatitis.

Hydrogen sulfide and substance P in inflammation

Hydrogen sulfide (H(2)S) plays an important role in cardiovascular, central nervous, and gastrointestinal systems. Being the third gaseous mediator, H(2)S has been shown to act as a vasodilator. In recent times, more and more attention has been paid to the biological functions of H(2)S in inflammation. Substance P is an 11 amino acid neuropeptide that is released from nerve endings in many tissues. Subsequent to its release, substance P binds to neurokinin-1 (NK-1) receptors on the surface of effector cells and, in addition to being a mediator of pain, it plays an important role in many inflammatory states including asthma, immune-complex-mediated lung injury, experimental arthritis, and inflammatory bowel disease. Substance P has been shown to increase microvascular permeability and promote plasma extravasation. Using animal models of inflammation of different etiologies such as acute pancreatitis, sepsis, and burns, studies in our laboratory have recently shown an important role of the pro-inflammatory action of H(2)S and substance P.

P2X7 receptor activation induces CXCL2 production in microglia through NFAT and PKC/MAPK pathways

Microglia plays an important role in many neurodegenerative conditions. ATP leaked or released by damaged cells triggers microglial activation through P2 receptors, and stimulates the release of oxygen radicals, proinflammatory cytokines and chemokines from activated microglia. However, little is known about mechanisms underlying ATP-induced chemokine release from microglia. In this study, we found that a high concentration of ATP induces the mRNA expression and release of CXCL2 from microglia. A similar effect was observed following treatment of microglia with a P2X7 receptor (P2X7R) agonist, 2'-and 3'-O-(4-benzoylbenzoyl) ATP, and this was inhibited by pre-treatment with a P2X7R antagonist, Brilliant Blue G. ATP induced both activation of nuclear factor of activated T cells (NFAT) and MAPKs (p38, ERK, and JNK) through P2X7R. ATP-induced mRNA expression of CXCL2 was inhibited by INCA-6 (an NFAT inhibitor), SB203580 (a p38 inhibitor), U0126 (a MEK-ERK inhibitor) and JNK inhibitor II (a JNK inhibitor). However, MAPK inhibitors did not inhibit activation of NFAT. In addition, protein kinase C inhibitors suppressed ATP-induced ERK and JNK activation, and also inhibited ATP-induced CXCL2 expression in microglia. These results suggest that ATP increased CXCL2 production via both NFAT and protein kinase C/MAPK signaling pathways through P2X7 receptor stimulation in microglia.

Cardiocirculatory pathophysiological mechanisms in severe acute pancreatitis

Acute pancreatitis (AP) is a common and potentially lethal acute inflammatory process. Although the majority of patients have a mild episode of AP, 10%-20% develop a severe acute pancreatitis (SAP) and suffer systemic inflammatory response syndrome (SIRS) and/or pancreatic necrosis. The main aim of this article is to review the set of events, first localized in the pancreas, that lead to pancreatic inflammation and to the spread to other organs contributing to multiorganic shock. The early pathogenic mechanisms in SAP are not completely understood but both premature activation of enzymes inside the pancreas, related to an impaired cytosolic Ca²⁺ homeostasis, as well as release of pancreatic enzymes into the bloodstream are considered important events in the onset of pancreatitis disease. Moreover, afferent fibers within the pancreas release neurotransmitters in response to tissue damage. The vasodilator effects of these neurotransmitters and the activation of pro-inflammatory substances play a crucial role in amplifying the inflammatory response, which leads to systemic manifestation of AP. Damage extension to other organs leads to SIRS, which is usually associated with cardiocirculatory physiology impairment and a hypotensive state. Hypotension is a risk factor for death and is associated with a significant hyporesponsiveness to vasoconstrictors. This indicates that stabilization of the patient, once this pathological situation has been established, would be a very difficult task. Therefore, it seems particularly necessary to understand the pathological mechanisms involved in the first phases of AP to avoid damage beyond the pancreas. Moreover, efforts must also be directed to identify those patients who are at risk of developing SAP.

Extracellular signal-regulated kinase 1/2 and c-Jun NH2-terminal kinase, through nuclear factor-kappaB and activator protein-1, contribute to caerulein-induced expression of substance P and neurokinin-1 receptors in pancreatic acinar cells

The neuropeptide substance P (SP) has emerged to be an important proinflammatory mediator in acute pancreatitis (AP). The presence of substance P and its receptor, neurokinin-1 receptor (NK1R) has been shown in the pancreas and the pancreatic acinar cells. In this study, we investigated the unexplored mechanisms that mediate SP and NK1R expression using an in vitro AP model. Pancreatic acinar cells were obtained from pancreas of male Swiss mice. Isolated cells were treated with caerulein to mimic secretagogue pancreatitis. A concentration-dependent study that subjected the cells to 60 min of stimulation by caerulein showed that SP and the transcript from its gene preprotachykinin-A (PPT-A), and NK1R were up-regulated at a supraphysiological concentration of 10(-7) M. A concentration-dependent study on intracellular kinases, extracellular signal-regulated kinase (ERK1/2), and c-Jun N-terminal kinase (JNK) and also transcription factors nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1) showed that they were activated when the caerulein concentration was 10(-7) M. Inhibition of JNK reversed the up-regulation of PPT-A, SP, and NK1R. However, inhibition of ERK1/2 reversed the up-regulation of NK1R but not of PPT-A and SP. Furthermore, we found that specific ERK1/2 and JNK inhibitors reduce NF-kappaB and AP-1 activity. Taken together, our results suggest that supraphysiological concentrations of caerulein up-regulate the expression of SP and NK1R in pancreatic acinar cells, and the signaling molecules that are involved in this up-regulation include ERK1/2, JNK, NF-kappaB, and AP-1.

Protein kinase C delta-mediated processes in cholecystokinin-8-stimulated pancreatic acini

OBJECTIVES

To define the role of protein kinase C delta (PKC delta) in acinar cell responses to the hormone cholecystokinin-8 (CCK) using isoform-specific inhibitors and a previously unreported genetic deletion model.

METHODS

Pancreatic acinar cells were isolated from (1) rat, and pretreated with a PKC delta-specific inhibitor or (2) PKC delta-deficient and wild type mice. Isolated cells were stimulated with CCK (0.001-100 nmol/L) and cell responses were measured.

RESULTS

The PKC delta inhibitor did not affect stimulated amylase secretion from rat pancreatic acinar cells. Cholecystokinin-8 stimulation induced a typical biphasic dose-response curve for amylase secretion in acinar cells isolated from both PKC delta(-/-) and wild type mice, with maximal stimulation at 10-pmol/L CCK. Cholecystokinin-8 (100 nmol/L) induced zymogen and nuclear factor kappaB activation in both PKC delta(-/-) and wild type mice, although it was up to 50% less in PKC delta(-/-).

CONCLUSIONS

In contrast to previous studies, this study has used specific and complementary approaches to examine PKC delta-mediated acinar cell responses. We could not confirm that it mediates amylase release but corroborated its role in the early stages of acute pancreatitis.

The role of redox status on chemokine expression in acute pancreatitis

This study focused on the involvement of oxidative stress in the mechanisms mediating chemokine production in different cell sources during mild and severe acute pancreatitis (AP) induced by bile-pancreatic duct obstruction (BPDO) and 3.5% NaTc, respectively. N-Acetylcysteine (NAC) was used as antioxidant treatment. Pancreatic glutathione depletion, acinar overexpression of monocyte chemoattractant protein-1 (MCP-1) and cytokine-induced neutrophil chemoattractant (CINC), and activation of p38MAPK, NF-kappaB and STAT3 were found in both AP models. NAC reduced the depletion of glutathione in BPDO- but not in NaTc-induced AP, in which oxidative stress overwhelmed the antioxidant capability of NAC. As a result, inhibition of the acinar chemokine expression and signalling pathways occurs in mild, but not in severe AP. However, MCP-1 and CINC expressions in whole pancreas and plasma chemokine levels were not reduced by NAC, even in BPDO-induced AP, suggesting that in addition to acini, other pancreatic cells produced chemokines by antioxidant resistant mechanisms. The high Il-6 plasma levels found during AP, both in NAC-treated and non-treated rats, pointed out cytokines as activating factors of chemokine expression in non-acinar cells. In conclusion, from early AP oxidant-mediated MAPK, NF-kappaB and STAT3 activation triggers the chemokine expression in acini but not in non-acinar cells.

Murine pancreatic duct ligation induces stress kinase activation, acute pancreatitis, and acute lung injury

BACKGROUND

Acute lung injury is a major determinant of outcomes in acute pancreatitis. We evaluated acute lung injury and stress kinase activation in ligation-induced acute pancreatitis in mice.

METHODS

Mice with duct ligation or sham operation were killed after 24 or 48 hours.

RESULTS

In addition to acute pancreatitis, duct ligation was associated with pulmonary morphologic changes indicative of acute lung injury (alveolar septal thickening, congestion, and neutrophil infiltration). Furthermore, immunoblotting showed stress kinase activation in the pancreas and lung after ligation. Although mortality was observed in the ligated group, that is consistent with severe lung injury, it requires further evaluation.

CONCLUSIONS

Bile and pancreatic duct ligation in the mouse is associated with pancreatic and pulmonary stress kinase activation and acute inflammatory changes consistent with early acute pancreatitis and acute lung injury. Our findings are important as acute lung injury increases mortality in clinical acute pancreatitis and stress kinases are established proinflammatory signal transducers.

Molecular basis for pancreatitis

PURPOSE OF REVIEW

This timely review will focus on clinical and basic science studies that have greatly advanced our knowledge of the molecular mechanisms of both acute pancreatitis and chronic pancreatitis over the last year.

RECENT FINDINGS

Animal models of both severe acute pancreatitis and chronic pancreatitis have recently been developed. Several unexpected protective mechanisms, mediated by the protease activated receptor 2 and heat shock protein 70, have been described. A genetic study suggested that polymorphisms in toll-like receptor-4 might affect the risk of developing infections in acute pancreatitis. Studies of chronic pancreatitis have shown that specific neural receptors, transient receptor potential vanilloid subtype 1, mediate pain responses in a model of chronic pancreatitis. The pancreatic zymogen, chymotrypsin C, can degrade pathologically activated trypsin in the acinar cell. Inactivating mutations in chymotrypsin C have been reported to predispose to the development of chronic pancreatitis, especially in those who are prone to alcohol abuse.

SUMMARY

The implications of the last year's findings are widespread. Improved animal models of acute pancreatitis and chronic pancreatitis will be critical for performing pilot studies of therapy. A greater understanding of genetic factors and pain responses could lead to potential treatments. This review will first discuss issues related to acute pancreatitis, and then conclude with studies most relevant to chronic disease.