Ca2+ and protein kinase C activation of mucin granule exocytosis in permeabilized SPOC1 cells

Abnormal neonatal sodium handling in skin precedes hypertension in the SAME rat

We discovered high Na⁺ and water content in the skin of newborn Sprague–Dawley rats, which reduced ~ 2.5-fold by 7 days of age, indicating rapid changes in extracellular volume (ECV). Equivalent changes in ECV post birth were also observed in C57Bl/6 J mice, with a fourfold reduction over 7 days, to approximately adult levels. This established the generality of increased ECV at birth. We investigated early sodium and water handling in neonates from a second rat strain, Fischer, and an Hsd11b2-knockout rat modelling the syndrome of apparent mineralocorticoid excess (SAME). Despite Hsd11b2^−/− animals exhibiting lower skin Na⁺ and water levels than controls at birth, they retained ~ 30% higher Na⁺ content in their pelts at the expense of K⁺ thereafter. Hsd11b2^−/− neonates exhibited incipient hypokalaemia from 15 days of age and became increasingly polydipsic and polyuric from weaning. As with adults, they excreted a high proportion of ingested Na⁺ through the kidney, (56.15 ± 8.21% versus control 34.15 ± 8.23%; n = 4; P < 0.0001), suggesting that changes in nephron electrolyte transporters identified in adults, by RNA-seq analysis, occur by 4 weeks of age. Our data reveal that Na⁺ imbalance in the Hsd11b2^−/− neonate leads to excess Na⁺ storage in skin and incipient hypokalaemia, which, together with increased, glucocorticoid-induced Na⁺ uptake in the kidney, then contribute to progressive, volume contracted, salt-sensitive hypertension. Skin Na⁺ plays an important role in the development of SAME but, equally, may play a key physiological role at birth, supporting post-natal growth, as an innate barrier to infection or as a rudimentary kidney.

The Long Road to the Development of Effective Therapies for the Short Gut Syndrome: A Personal Perspective

The ability to provide parenteral support represents a revolutionary change in medical therapy for patients with temporary and inadequate intestinal absorptive capacity or for patients with chronic intestinal failure due to digestive diseases. Nevertheless, due to the rarity of intestinal failure, a de facto policy of "discrimination by organ failure treatment" exists in many countries whereby this problem is under-recognized and under-treated. With the increasing recognition of the pathophysiological consequences of intestinal resection and the occurrence of new pro-adaptive treatments for patients suffering from short bowel syndrome, this review reflects on the history of developments in this area and discusses current practice and future directions of the field.

Regulation of Cellular Redox Signaling by Matricellular Proteins in Vascular Biology, Immunology, and Cancer

SIGNIFICANCE

In contrast to structural elements of the extracellular matrix, matricellular proteins appear transiently during development and injury responses, but their sustained expression can contribute to chronic disease. Through interactions with other matrix components and specific cell surface receptors, matricellular proteins regulate multiple signaling pathways, including those mediated by reactive oxygen and nitrogen species and H2S. Dysregulation of matricellular proteins contributes to the pathogenesis of vascular diseases and cancer. Defining the molecular mechanisms and receptors involved is revealing new therapeutic opportunities. Recent Advances: Thrombospondin-1 (TSP1) regulates NO, H2S, and superoxide production and signaling in several cell types. The TSP1 receptor CD47 plays a central role in inhibition of NO signaling, but other TSP1 receptors also modulate redox signaling. The matricellular protein CCN1 engages some of the same receptors to regulate redox signaling, and ADAMTS1 regulates NO signaling in Marfan syndrome. In addition to mediating matricellular protein signaling, redox signaling is emerging as an important pathway that controls the expression of several matricellular proteins.

CRITICAL ISSUES

Redox signaling remains unexplored for many matricellular proteins. Their interactions with multiple cellular receptors remains an obstacle to defining signaling mechanisms, but improved transgenic models could overcome this barrier.

FUTURE DIRECTIONS

Therapeutics targeting the TSP1 receptor CD47 may have beneficial effects for treating cardiovascular disease and cancer and have recently entered clinical trials. Biomarkers are needed to assess their effects on redox signaling in patients and to evaluate how these contribute to their therapeutic efficacy and potential side effects. Antioxid. Redox Signal. 27, 874-911.

Involvement of the accumbal osteopontin-interacting transmembrane protein 168 in methamphetamine-induced place preference and hyperlocomotion in mice

Chronic exposure to methamphetamine causes adaptive changes in brain, which underlie dependence symptoms. We have found that the transmembrane protein 168 (TMEM168) is overexpressed in the nucleus accumbens of mice upon repeated methamphetamine administration. Here, we firstly demonstrate the inhibitory effect of TMEM168 on methamphetamine-induced behavioral changes in mice, and attempt to elucidate the mechanism of this inhibition. We overexpressed TMEM168 in the nucleus accumbens of mice by using an adeno-associated virus vector (NAc-TMEM mice). Methamphetamine-induced hyperlocomotion and conditioned place preference were attenuated in NAc-TMEM mice. Additionally, methamphetamine-induced extracellular dopamine elevation was suppressed in the nucleus accumbens of NAc-TMEM mice. Next, we identified extracellular matrix protein osteopontin as an interacting partner of TMEM168, by conducting immunoprecipitation in cultured COS-7 cells. TMEM168 overexpression in COS-7 cells induced the enhancement of extracellular and intracellular osteopontin. Similarly, osteopontin enhancement was also observed in the nucleus accumbens of NAc-TMEM mice, in in vivo studies. Furthermore, the infusion of osteopontin proteins into the nucleus accumbens of mice was found to inhibit methamphetamine-induced hyperlocomotion and conditioned place preference. Our studies suggest that the TMEM168-regulated osteopontin system is a novel target pathway for the therapy of methamphetamine dependence, via regulating the dopaminergic function in the nucleus accumbens.

Aquaporins in Urinary System

Several aquaporin (AQP )-type water channels are expressed in kidney: AQP1 in the proximal tubule, thin descending limb of Henle, and vasa recta; AQP2 -6 in the collecting duct; AQP7 in the proximal tubule; AQP8 in the proximal tubule and collecting duct; and AQP11 in the endoplasmic reticulum of proximal tubule cells. AQP2 is the vasopressin-regulated water channel that is important in hereditary and acquired diseases affecting urine-concentrating ability. The roles of AQPs in renal physiology and transepithelial water transport have been determined using AQP knockout mouse models. This chapter describes renal physiologic insights revealed by phenotypic analysis of AQP knockout mice and the prospects for further basic and clinical studies.

Short Bowel Syndrome and Intestinal Failure in Crohn's Disease

Crohn's disease is a chronic and progressive inflammatory disorder of the gastrointestinal tract. Despite the availability of powerful immunosuppressants, many patients with Crohn's disease still require one or more intestinal resections throughout the course of their disease. Multiple resections and a progressive reduction in bowel length can lead to the development of short bowel syndrome, a form of intestinal failure that compromises fluid, electrolyte, and nutrient absorption. The pathophysiology of short bowel syndrome involves a reduction in intestinal surface area, alteration in the enteric hormonal feedback, dysmotility, and related comorbidities. Most patients will initially require parenteral nutrition as a primary or supplemental source of nutrition, although several patients may eventually wean off nutrition support depending on the residual gut anatomy and adherence to medical and nutritional interventions. Available surgical treatments focus on reducing motility, lengthening the native small bowel, or small bowel transplantation. Care of these complex patients with short bowel syndrome requires a multidisciplinary approach of physicians, dietitians, and nurses to provide optimal intestinal rehabilitation, nutritional support, and improvement in quality of life.

Intranasal Delivery of RGD Motif-Containing Osteopontin Icosamer Confers Neuroprotection in the Postischemic Brain via αvβ3 Integrin Binding

Osteopontin (OPN) is a phosphorylated glycoprotein possessing an arginine-glycine-aspartate (RGD)-motif, which binds to several cell surface integrins and mediates a wide range of cellular processes. Inductions of OPN have been reported in the postischemic brain, and the neuroprotective effects of OPN have been demonstrated in animal models of stroke. In the present study, we showed a robust neuroprotective effect of RGD-containing icosamer OPN peptide (OPNpt20) in a rat model of focal cerebral ischemia (middle cerebral artery occlusion, MCAO). Intranasally administered OPNpt20 reduced mean infarct volume by 79.7 % compared to the treatment-naïve MCAO control animals and markedly ameliorated neurological deficits. In addition, OPNpt20 significantly suppressed the inductions of iNOS and of inflammatory markers in postischemic brains and in primary microglial cultures, demonstrating anti-inflammatory effects. Administration of a mutant peptide, in which RGD was replaced by arginine-alanine-alanine (RAA), failed to suppress infarct volumes in MCAO animals and co-administration of OPNpt20 with anti-αvβ3 integrin antibody failed to suppress iNOS induction in primary microglia culture, indicating that the RGD motif in OPNpt20 and endogenous αvβ3 integrin play critical roles. Furthermore, pull-down assay revealed a direct binding between OPNpt20 and αvβ3 integrin in primary microglia culture. Together, these results indicate that RGD-containing OPN icosamer has therapeutic potential in the postischemic brain and αvβ3 integrin-mediated anti-inflammatory effect might be an underlying mechanism.

Dipeptidyl peptidase IV inhibition prevents the formation and promotes the healing of indomethacin-induced intestinal ulcers in rats

BACKGROUNDS AND AIMS

We studied the intestinotrophic hormone glucagon-like peptide-2 (GLP-2) as a possible therapy for non-steroidal anti-inflammatory drug (NSAID)-induced intestinal ulcers. Luminal nutrients release endogenous GLP-2 from enteroendocrine L cells. Since GLP-2 is degraded by dipeptidyl peptidase IV (DPPIV), we hypothesized that DPPIV inhibition combined with luminal administration of nutrients potentiates the effects of endogenous GLP-2 on intestinal injury.

METHODS

Intestinal injury was induced by indomethacin (10 mg/kg, sc) in fed rats. The long-acting DPPIV inhibitor K579 was given intragastrically (ig) or intraperitoneally (ip) before or after indomethacin treatment. L-Alanine (L-Ala) and inosine 5'-monophosphate (IMP) were co-administered ig after the treatment.

RESULTS

Indomethacin treatment induced intestinal ulcers that gradually healed after treatment. Pretreatment with ig or ip K579 given at 1 mg/kg reduced total ulcer length, whereas K579 at 3 mg/kg had no effect. Exogenous GLP-2 also reduced intestinal ulcers. The preventive effect of K579 was dose-dependently inhibited by a GLP-2 receptor antagonist. Daily treatment with K579 (1 mg/kg), GLP-2, or L-Ala + IMP after indomethacin treatment reduced total ulcer length. Co-administration (ig) of K579 and L-Ala + IMP further accelerated intestinal ulcer healing.

CONCLUSION

DPPIV inhibition and exogenous GLP-2 prevented the formation and promoted the healing of indomethacin-induced intestinal ulcers, although high-dose DPPIV inhibition reversed the preventive effect. Umami receptor agonists also enhanced the healing effects of the DPPIV inhibitor. The combination of DPPIV inhibition and luminal nutrient-induced GLP-2 release may be a useful therapeutic tool for the treatment of NSAIDs-induced intestinal ulcers.

Pharmacologic options for intestinal rehabilitation in patients with short bowel syndrome

A primary goal of intestinal rehabilitation programs is to facilitate intestinal adaptation. Adult patients with short bowel syndrome (SBS) who are dependent on parenteral nutrition and/or intravenous fluid (PN/IV) support have 2 hormonal pharmacologic treatment options available that may promote intestinal growth: a glucagon-like peptide 2 analog (teduglutide) and recombinant human growth hormone (somatropin). In two phase III clinical trials (N=169), 24 weeks of teduglutide administered to outpatients with SBS resulted in significant decreases in PN/IV volume requirements of 2.5-4.4 L/wk. In an extension study of one of these trials, patients with SBS who completed 30 months of teduglutide experienced a mean PN/IV reduction of 7.6 L/wk from baseline. Furthermore, some patients achieved independence from PN/IV support. The most common adverse events associated with teduglutide treatment in clinical trials were gastrointestinal symptoms, including abdominal distension, abdominal pain, and nausea. This safety profile is consistent with the associated underlying diseases leading to SBS or the known mechanism of action of teduglutide. A single phase III study (N=41) evaluated the safety and efficacy of a 4-week inpatient course of somatropin in combination with a glutamine-supplemented diet for adults with SBS. Somatropin treatment significantly reduced parenteral support requirements by 1.1 L/d in these patients. The most common adverse events were peripheral edema and musculoskeletal events. Large-scale, long-term follow-up studies of somatropin for SBS have not been conducted. Although treatment for patients with SBS must be individualized, teduglutide and somatropin are positive extensions to existing fluid and nutrient management strategies.

GLP2-2G-XTEN: a pharmaceutical protein with improved serum half-life and efficacy in a rat Crohn's disease model

OBJECTIVES

Glucagon-like peptide 2 (GLP2) is an intestinal growth factor that has been shown to stimulate intestinal growth and reduce disease severity in preclinical models of short bowel syndrome and inflammatory bowel disease. Teduglutide, a recombinant human GLP2 variant (GLP2-2G), has increased half-life and stability as compared to the native GLP2 peptide, but still requires twice daily dosing in preclinical models and daily dosing in the clinic. The goal of this study was to produce and characterize the preclinical pharmacokinetic and therapeutic properties of GLP2-2G-XTEN, a novel, long-acting form of GLP2-2G.

METHODOLOGY AND RESULTS

A GLP2-2G-XTEN fusion protein with extended exposure profile was produced by genetic fusion of GLP2-2G peptide to XTEN, a long, unstructured, non-repetitive, hydrophilic sequence of amino acids. The serum half-life of GLP2-2G-XTEN in mice, rats and monkeys was 34, 38 and 120 hours, respectively. Intestinotrophic effects were demonstrated in normal rats, where GLP2-2G-XTEN administration resulted in a significant increase in both small intestine weight and length. Efficacy of the GLP2-2G-XTEN protein was compared to that of GLP2-2G peptide in a rat Crohn's disease model, indomethacin-induced inflammation. Prophylactic administration of GLP2-2G-XTEN significantly increased the length, reduced the number of trans-ulcerations and adhesions, and reduced the TNFα content of the small intestine. GLP2-2G-XTEN demonstrated greater in vivo potency as compared to GLP2-2G peptide, and improvement in histopathology supported the GLP2-2G-XTEN treatment effects.

CONCLUSIONS AND SIGNIFICANCE

GLP2-2G-XTEN is intestinotrophic and demonstrates efficacy in a rat Crohn's disease model requiring a lower molar dose and less frequent dosing relative to GLP2-2G peptide. Allometric scaling based on pharmacokinetics from mouse, rat and monkey projects a human half-life of 240 hours. These improvements in preclinical pharmacokinetics and dosing indicate that GLP2-2G-XTEN may offer a superior therapeutic benefit for treatment of gastrointestinal diseases including Crohn's disease.

Serum levels of calcification inhibitors in patients with intracerebral hemorrhage

The vascular calcification regulators and inflammatory markers including fetuin-A, osteopontin (OPN), and matrix Gla protein (MGP) may play an important role in the development of intracerebral hemorrhages (ICHs). So far, the relationship between these parameters and ICH has not been studied. Therefore, this study was designed to elucidate whether fetuin-A, MGP, and OPN are involved in the pathophysiology of ICH. The ICH group consisted of 27 consecutive patients with spontaneous ICH evaluated in the neurology intensive care unit within the first 24 hours from the onset of the stroke. The serum OPN levels were significantly increased in patients with ICH compared to the controls. On the other hand, the serum MGP and fetuin-A levels were significantly decreased in the patients with ICH in comparison to the controls. In the patients with ICH, the serum MGP levels of the nonsurvivors were statistically significantly lower than the MGP levels of the survivors. In conclusion, the change in serum fetuin-A, MGP, and OPN levels after ICH indicates that these parameters play a role in the pathophysiological processes leading to an ICH. Measurement of the serum MGP levels may also be of value to estimate mortality.

Teduglutide for the treatment of short bowel syndrome

Extensive resection of the intestine impairs its absorptive capacity and results in short bowel syndrome when the nutritional equilibrium is compromised. The remnant intestine adapts structurally to compensate, but nutritional autonomy cannot be achieved in patients with intestinal failure, requiring intravenous fluids and parenteral nutrition (PN) for sustenance of life. PN is expensive and associated with serious complications. Efforts to minimize or eliminate the need for PN heralded research focusing on the therapeutic utility of intrinsic gut factors involved in the postresection adaptation process. With the breakthrough recognition of the intestinotrophic properties of glucagon-like peptide-2, teduglutide, a recombinant analogue of glucagon-like peptide-2, is being investigated as a promising hope to mitigate the requirement of PN. Clinical studies to date have demonstrated a desirable benefit-to-risk profile in regards to its safety and efficacy. If approved for marketing, it will be the first of its class in short bowel syndrome management, offering an innovative therapeutic modality for this debilitating condition.

Does low testosterone affect adaptive properties of adipose tissue in obese men?

Obesity and (pre)diabetes in males is associated with low serum testosterone and increased oestradiol levels. It is unknown whether these changes in sex steroids are part of a vicious circle resulting in an increase of risk for metabolic complications of obesity, or whether it presents merely an epiphenomenon. The risk for metabolic complications in obesity seems to be determined by adaptation and integrity of adipose tissue. It is unknown whether the typical changes in sex steroids seen in obese men are desirable or ominous with respect to these functions. However, it might be clinically relevant, as low serum testosterone can be treated, and well with different forms of interventional therapy. The present review provides a short summary on findings, obstacles and future research needed to gain better insight into consequences of changes in sex steroids for adaptation of adipose tissue in obese men.

Nucleotide-mediated airway clearance

A thin layer of airway surface liquid (ASL) lines the entire surface of the lung and is the first point of contact between the lung and the environment. Surfactants contained within this layer are secreted in the alveolar region and are required to maintain a low surface tension and to prevent alveolar collapse. Mucins are secreted into the ASL throughout the respiratory tract and serve to intercept inhaled pathogens, allergens and toxins. Their removal by mucociliary clearance (MCC) is facilitated by cilia beating and hydration of the ASL by active ion transport. Throughout the lung, secretion, ion transport and cilia beating are under purinergic control. Pulmonary epithelia release ATP into the ASL which acts in an autocrine fashion on P2Y(2) (ATP) receptors. The enzymatic network describes in Chap. 2 then mounts a secondary wave of signaling by surface conversion of ATP into adenosine (ADO), which induces A(2B) (ADO) receptor-mediated responses. This chapter offers a comprehensive description of MCC and the extensive ramifications of the purinergic signaling network on pulmonary surfaces.

Reciprocal interaction with G-actin and tropomyosin is essential for aquaporin-2 trafficking

Trafficking of water channel aquaporin-2 (AQP2) to the apical membrane and its vasopressin and protein kinase A (PKA)–dependent regulation in renal collecting ducts is critical for body water homeostasis. We previously identified an AQP2 binding protein complex including actin and tropomyosin-5b (TM5b). We show that dynamic interactions between AQP2 and the actin cytoskeleton are critical for initiating AQP2 apical targeting. Specific binding of AQP2 to G-actin in reconstituted liposomes is negatively regulated by PKA phosphorylation. Dual color fluorescence cross-correlation spectroscopy reveals local AQP2 interaction with G-actin in live epithelial cells at single-molecule resolution. Cyclic adenosine monophosphate signaling and AQP2 phosphorylation release AQP2 from G-actin. In turn, AQP2 phosphorylation increases its affinity to TM5b, resulting in reduction of TM5b bound to F-actin, subsequently inducing F-actin destabilization. RNA interference–mediated knockdown and overexpression of TM5b confirm its inhibitory role in apical trafficking of AQP2. These findings indicate a novel mechanism of channel protein trafficking, in which the channel protein itself critically regulates local actin reorganization to initiate its movement.

Protein kinase C delta regulates airway mucin secretion via phosphorylation of MARCKS protein

Mucin hypersecretion is a major pathological feature of many respiratory diseases, yet cellular mechanisms regulating secretion of mucin have not been fully elucidated. Previously, we reported that mucin hypersecretion induced by human neutrophil elastase involves activation of protein kinase C (PKC), specifically the delta-isoform (PKC delta). Here, we further investigated the role of PKC delta in mucin hypersecretion using both primary human bronchial epithelial cells and the human bronchial epithelial 1 cell line as in vitro model systems. Phorbol-12-myristate-13-acetate (PMA)-induced mucin hypersecretion was significantly attenuated by rottlerin, a PKC delta-selective inhibitor. Rottlerin also reduced PMA- or human neutrophil elastase-induced phosphorylation of myristoylated alanine-rich C kinase substrate (MARCKS) protein in these cells. Both secretion and MARCKS phosphorylation were significantly enhanced by the PKC delta activator bryostatin 1. A dominant-negative PKC delta construct (pEGFP-N1/PKC delta K376R) transfected into human bronchial epithelial 1 cells significantly attenuated both PMA-induced mucin secretion and phosphorylation of MARCKS, whereas transfection of a wild-type construct increased PKC delta and enhanced mucin secretion and MARCKS phosphorylation. Similar transfections of a dominant-negative or wild-type PKC epsilon construct did not affect either mucin secretion or MARCKS phosphorylation. The results suggest that PKC delta plays an important role in mucin secretion by airway epithelium via regulation of MARCKS phosphorylation.

Differential Down-Regulation of Aquaporin-2 in Rat Kidney Zones by Peripheral Nociceptin/Orphanin FQ Receptor Agonism and Vasopressin Type-2 Receptor Antagonism

We previously showed that aquaresis induced by the peripherally acting nociceptin/orphanin FQ receptor agonist ZP120 is associated with a decreased protein level of aquaporin-2 (AQP2) in whole-kidney homogenates. We now examined the effects of Ac-RYYRWKKKKKKK-NH(2) (ZP120) (1 nmol/kg/min i.v. for 4 h) on renal regional expression (cortex/outer stripe of outer medulla, inner stripe of outer medulla, and inner medulla) and subcellular localization of aquaporin-2. Responses to ZP120 were compared to the effects of an equi-aquaretic dose ( approximately 40% inhibition of distal water reabsorption) of the vasopressin type-2 receptor antagonist 5-dimethylamine-1-[4-(2-methylbenzoylamino)benzoyl]-2,3,4,5-tetrahydro-1H-benzapine (OPC31260) (32 nmol/kg/min). ZP120 decreased the aquaporin-2 protein level in the rat cortex/outer stripe of outer medulla and decreased apical plasma membrane localization of aquaporin-2 in the cortex (P = 0.002) and in the inner medulla (P = 0.06). These effects were not accompanied by a decrease in the aquaporin-2 mRNA level. OPC31260-induced aquaresis was associated with a decreased aquaporin-2 protein level in both the cortex/outer stripe of outer medulla and in the inner stripe of outer medulla. Apical localization of aquaporin-2 was decreased throughout all kidney zones, and OPC31260 decreased the AQP2 mRNA level in the inner medulla. We conclude that equi-aquaretic doses of ZP120 and OPC31260 produce different patterns of aquaporin-2 down-regulation, suggesting different signaling pathways.

Emerging drugs for acute and chronic heart failure: current and future developments

Heart failure continues to be a major public health issue. Although angiotensin-converting enzyme inhibitors and beta-adrenergic blockers have been broadly used as evidence-based therapies in heart failure, morbidity and mortality remains high. Furthermore, treatment for acute decompensated heart failure and diastolic heart failure (or 'heart failure with preserved ejection fraction') is far from perfect. This review provides a broad overview of some of the novel compounds under investigation for the treatment of heart failure. Novel strategies include drugs that aim to alleviate congestion and improve hemodynamics, drugs that preserve renal function, drugs that reduce arterial and myocardial stiffness, drugs that module myocardial contractility, drugs that affect metabolic and hormonal balance, and drugs that act on existing and novel physiologic targets.

Nitric oxide induces MUC5AC mucin in respiratory epithelial cells through PKC and ERK dependent pathways

Background

Nitric oxide (NO) is generally increased during inflammatory airway diseases. This increased NO stimulates the secretion of mucin from the goblet cell and submucosal glands but the mechanism is still unknown precisely. In this study, we investigated potential signaling pathways involving protein kinase C (PKC) and mitogen-activated protein kinase (MAPK) in the NO-induced MUC5AC mucin gene and protein expression in A549 cells.

Methods

Nitric oxide was donated to the A549 cells by NOR-1. MUC5AC mucin levels were assayed by enzyme-linked immunosorbent assay (ELISA). MUC5AC promoter activity was determined by measuring luciferase activity after the lysing the transfected cells. Activation of PKC isoforms were measured by assessing the distribution of the enzyme between cytosolic and membrane fractions using immunoblotting. Immunoblotting experiments using a monoclonal antibody specific to PKC isoforms were performed in the cytosol and membrane fractions from A549 cells. Western blot analysis for pERK and p38 were performed using the corresponding antibodies from the cell lysates after donating NO to the A549 cells by NOR-1.

Results

The transcriptional activity of MUC5AC promoter was maximal at the concentration of 0.1 mM NOR-1 for 1 hour incubation in transfected A549 cells. (±)-(E)-methyl-2-((E)-hydroxyimino)-5-nitro-6-methoxy-3-hexenamide (NOR-1) markedly displaced the protein kinase C (PKC)α and PKCδ from the cytosol to the membrane. Furthermore, the PKC-α,βinhibitors, GÖ6976 (10 nM) and PKCδ inhibitors, rottlerin (4 μM) inhibited the NOR-1 induced migration of PKCα and PKCδ respectively. NOR-1 also markedly increased the MUC5AC promoter activity and mRNA expression, mucin synthesis and ERK1/2 phosphorylation. The PKC inhibitors also inhibited the NOR-1 induced MUC5AC mRNA and MUC5AC protein synthesis by inhibiting the activation of PKCα and PKCδ with ERK1/2 pathways.

Conclusion

Exogenous NO induced the MUC5AC mucin gene and protein through the PKCα and PKCδ – ERK pathways in A549 cells. Inhibition of PKC attenuated NO-mediated MUC5AC mucin synthesis. In view of this findings, PKC inhibitors might be useful in the treatment of bronchial asthma and chronic bronchitis patients where NO and mucus are increased in the bronchial airways.

Age-dependent regulation of chromaffin cell proliferation by growth factors, dehydroepiandrosterone (DHEA), and DHEA sulfate

The adrenal gland comprises two endocrine tissues of distinct origin, the catecholamine-producing medulla and the steroid-producing cortex. The inner adrenocortical zone, which is in direct contact with the adrenomedullary chromaffin cells, produces dehydroepiandrostendione (DHEA) and DHEA sulfate (DHEAS). These two androgens exhibit potential effects on neurogenesis, neuronal survival, and neuronal stem cell proliferation. Unlike the closely related sympathetic neurons, chromaffin cells are able to proliferate throughout life. The aim of this study was to investigate the effect of DHEA and DHEAS on proliferation of bovine chromaffin cells from young and adult animals. We demonstrated that graded concentrations of leukemia inhibitory factor induced proliferation of chromaffin cells from young animals, whereas EGF had no effect. On the contrary, EGF increased the cell proliferation in cells from adult animals, whereas leukemia inhibitory factor was inactive. In both cases, DHEA decreased the proliferative effect induced by the growth factors. Surprisingly, DHEAS enhanced, in a dose-dependent-manner, the effect of growth factors on proliferation in cells from adult animals but not from young animals. Flutamide, ICI 182,780, and RU 486 had no effect on the action of DHEA or DHEAS on chromaffin cell proliferation. These data show that DHEA and its sulfated form, DHEAS, differentially regulate growth-factor-induced proliferation of bovine chromaffin cells. In addition, the sensitivity of chromaffin cells to different growth factors is age-dependent. Furthermore, these two androgens may act through a receptor other than the classical steroid receptors.

The mechanistic basis of infarct healing

Myocardial infarction triggers an inflammatory cascade that results in healing and replacement of the damaged tissue with scar. Cardiomyocyte necrosis triggers innate immune mechanisms eliciting Toll-like receptor- mediated responses, activating the complement cascade and generating reactive oxygen species. Subsequent activation of NF-kappaB is a critical element in the regulation of cytokine, chemokine, and adhesion molecule expression in the ischemic myocardium. Chemokine induction mediates leukocyte recruitment in the myocardium. Pleiotropic proinflammatory cytokines, such as TNF-alpha, IL-1, and IL-6, are also upregulated in the infarct and exert a wide range of effects on a variety of cell types. Timely repression of proinflammatory gene synthesis is crucial for optimal healing; IL-10 and TGF-beta-mediated pathways may be important for suppression of chemokine and cytokine expression and for resolution of the leukocytic infiltrate. In addition, TGF-beta may be critically involved in inducing myofibroblast differentiation and activation, promoting extracellular matrix protein deposition in the infarcted area. The composition of the extracellular matrix plays an important role in regulating cell behavior. Both structural and matricellular proteins modulate cell signaling through interactions with specific surface receptors. The molecular and cellular changes associated with infarct healing directly influence ventricular remodeling and affect prognosis in patients with myocardial infarction.

Glucagon-like Peptide-2

Multiple peptide hormones produced within the gastrointestinal system aid in the regulation of energy homeostasis and metabolism. Among these is the intestinotrophic peptide glucagon-like peptide-2 (GLP-2), which is released following food intake and plays a significant role in the adaptive regulation of bowel mass and mucosal integrity. The discovery of GLP-2's potent growth-promoting and cytoprotective effects in the gastrointestinal (GI) tract stimulated interest in its use as a therapeutic agent for the treatment of GI diseases involving malabsorption, inflammation, and/or mucosal damage. Current research has focused on determining the physiological mechanisms contributing to the effects of GLP-2 and factors regulating its biological mechanisms of action. This chapter provides an overview of the biology of GLP-2 with a focus on the most recent findings on the role of this peptide hormone in the normal and diseased GI tract.

Lipid malabsorption persists after weaning in rats whose dams were given GLP-2 and dexamethasone

Glucagon-like peptide-2 (GLP-2) enhances intestinal growth and absorption in mature animals, and glucocorticosteroids (GC) increase the sugar and lipid uptake in adult animals. However, the role of GC and GLP-2 in the ontogeny of lipid absorption is unknown. We hypothesized that GLP-2 and the GC dexamethasone (DEX), when administrated to rat dams during pregnancy and lactation, would enhance lipid uptake in the offspring. Rat dams were treated in the last 10 d of pregnancy and during lactation with GLP-2 [0.1 microg/g/d subcutaneous (sc)], DEX (0.128 microg/g/d sc), GLP-2 + DEX, or a placebo. Sucklings were sacrificed at 19-21 d of age, and weanlings were sacrificed 4 wk later. Lipid uptake was assessed using an in vitro ring uptake method. Although DEX and GLP-2 + DEX increased the jejunal mass, the jejunal lipid uptake was unchanged. In contrast, GLP-2, DEX, and GLP-2 + DEX reduced the ileal lipid uptake in suckling and weanling rats. This reduction was not due to alterations in intestinal morphology or to changes in fatty acid-binding protein abundance, but it was partially explained by an increase in the effective resistance of the intestinal unstirred water layer. In sucklings, DEX dramatically reduced the jejunal lipid uptake to levels similar to those seen in weanlings, such that the normal ontogenic decline in lipid uptake was not observed. Giving dams GLP-2 or DEX during pregnancy and lactation reduced lipid uptake in the offspring, and this persisted for at least 1 mon. The impact this may have on the nutritional well-being of the animal in later life is unknown.

New growth factor therapies aimed at improving intestinal adaptation in short bowel syndrome

Short bowel syndrome (SBS) is used to describe a condition of malabsorption and malnutrition resulting from the loss of absorptive area following massive small bowel resection. The key to improved clinical outcome after massive small bowel resection is the ability of the residual bowel to adapt. Although still in experimental stages, a major goal in the management of SBS may be the augmented use of growth factors to promote increased adaptation. A number of growth factors have been implicated in promoting the adaptation process. The best-described growth factors are reviewed: glucagon-like peptide-2 (GLP-2), epidermal growth factor (EGF), and growth hormone (GH). This article reviews the ability of recombinant GLP-2, EGF and GH to modulate structural and functional aspects of intestinal adaptation following small bowel resection. Although these growth factors have shown promise, small sample size, inconsistent measurement parameters and uncontrolled study designs have hampered the acquisition of strong data advocating the use of growth factor treatment for SBS. Multicenter trials using well-defined outcome measures to assess clinical efficacy are needed to direct the clinical indications, timing and duration of therapy and assess potential risks associated with growth factor therapies.

Dehydroepiandrosterone and human adipose tissue

OBJECTIVE

The aim of this study was to investigate whether DHEA alters the proliferation and differentiation of human sc and visceral adipose cells in primary cultures.

METHOD

Sc and omental adipose tissue was obtained from 10 female donors aged 36+/-3.6 yr with a body mass index (BMI) of 33+/-3.21 kg/m2. Stromal vascular cells were isolated and cultured using modified procedures described by Entenmann and Hauner. For the proliferation assay, stromal-vascular cells from sc and visceral adipose tissue cultures were fed with proliferation media containing 0, 25 or 100 microM DHEA for 3 days. At the end of this treatment period, two type cultures were prepared for determining their metabolic activity using the sulforhodamine B staining procedure.

RESULTS

The metabolic activity of proliferating human visceral adipose tissue was higher than sc adipose tissue. The activity of proliferating human visceral tissue cultures decreased more than the sc tissue as the level of DHEA in the cultures was increased.

CONCLUSIONS

These data suggest that DHEA predominantly influences the proliferation and differentiation of human omental adipose tissue.

Human neutrophil elastase induces hypersecretion of mucin from well-differentiated human bronchial epithelial cells in vitro via a protein kinase C{delta}-mediated mechanism

The presence of mucus obstruction and neutrophil-predominant inflammation in several lung disorders, such as cystic fibrosis, suggests a relationship between neutrophils and excess mucus production. Mechanisms of human neutrophil elastase (HNE)-induced mucin secretion by well-differentiated normal human bronchial epithelial (NHBE) cells maintained in air/liquid interface culture were investigated. HNE increased mucin secretion in a concentration-dependent manner, with maximal stimulation (more than twofold) occurring within a short (15 minutes) time period. Mucins MUC 5 AC and MUC 5 B, but not MUC 2, were released in response to HNE. Stimulation of mucin secretion required partial elastase enzymatic activity and did not appear to involve a soluble product released by the cells. HNE-stimulated secretion involved activation of protein kinase C (PKC), as HNE exposure rapidly provoked PKC enzymatic activity that was attenuated by the general PKC inhibitors calphostin C and bisindoylmaleimide I. Of the different isoforms, PKCalpha, delta, zeta, lambda, iota, and epsilon were constitutively expressed in NHBE cells while PKCbeta, eta, and mu were PMA-inducible. PKCdelta was the only isoform to translocate from cytoplasm to membrane in response to HNE. Inhibition of PKCdelta attenuated HNE-mediated mucin secretion. The results suggest HNE stimulation of mucin release by human airway epithelial cells involves intracellular activation of PKC, specifically the delta isoform.

P2Y2 agonist induces mucin secretion via Ca2+- and inositol 1,4,5-triphosphate-dependent pathway in human middle ear epithelial cells

Purinergic agonists regulate mucin secretion in the airway epithelial cells. This study examined the effects of the apical application of purinergic agonists on Ca(2+) influx ([Ca(2+)](i)), and mucin secretion along with their underlying signaling pathway in normal human middle ear epithelial (NHMEE) cells. The apical membrane of NHMEE cells were stimulated with various purinergic agonists, including UTP, and the [Ca(2+)](i) was measured using a miniature Ussing double perfusion chamber. P2Y(2) receptor in NHMEE cells was also localized by immunohistochemistry. UTP-induced mucin secretion was quantified by an immunoblotting assay. The order of the purinergic agonist potency with respect to [Ca(2+)](i) determined in this study was ATP = UTP > 2-MeSATP > UDP >> adenosine which is consistent with that obtained from P2Y(2) receptor activation. The P2Y(2) receptor is expressed in the apical membrane of monolayered cultured NHMEE cells. Apical UTP-induced [Ca(2+)](i) was inhibited by 2-aminoethoxydiphenyl borate (2-APB) but not by ryanodine. UTP-induced mucin secretion was inhibited by a Ca(2+) chelating agent, BAPTA-AM, and was stimulated by ionomycin. UTP-induced mucin secretion was also suppressed by U73122 and 2-APB, while Calphostin C suppressed it to a small extent and PD98059 was ineffective. Caffeine also inhibited the UTP-induced [Ca(2+)](i) and mucin secretion. These results suggest that the P2Y(2) receptor is expressed in NHMEE cells, and plays a major role in modulating the [Ca(2+)](i) from the IP(3)-sensitive intracellular Ca(2+) store. UTP-induced mucin secretion in NHMEE cells is strongly dependent on Ca(2+)- and IP(3).

Development and resolution of experimental colitis in mice with targeted deletion of dipeptidyl peptidase IV

Glucagon-like peptide-2 (GLP-2) is a potent intestinotrophic growth factor that enhances repair of damaged intestinal tissue. However, its bioactivity is limited by dipeptidyl peptidase IV (DPIV)-mediated degradation. We hypothesized that DPIV(-/-) mice would display an increased resistance to, and an enhanced recovery from, dextran sulfate sodium (DSS)-induced colitis compared to DPIV(+/+) mice. DPIV(+/+) and DPIV(-/-) mice consumed 2% DSS for 6 days, followed by a 15 day recovery period. Mice were killed at days 0, 3, 6, 9, 14, and 21 (n = 6-8) and the small intestine and colon removed for histological assessment of villus height, crypt depth, and crypt area. The epithelial cell proliferative labeling index was determined by proliferating cell nuclear antigen (PCNA) immunostaining. Small intestine, colon, and total body weight did not differ between DPIV(+/+) and DPIV(-/-) mice. Distal colon crypt depth did not differ significantly between DPIV(+/+) and DPIV(-/-) mice during the development of DSS-colitis or during the recovery phase. Similarly no significant effects were apparent on distal colon crypt area or PCNA labeling index between DPIV(+/+) and DPIV(-/-) during the development of and recovery from DSS-colitis. However, DPIV(-/-) mice still possessed significant levels of plasma DPIV-like activity. We conclude that loss of DPIV activity does not increase resistance to experimental colitis and hypothesize that other DPIV family members may also be involved in the cleavage of GLP-2.

Harnessing the gut to treat diabetes

The gut contains one of the largest stem cell populations in the body, yet has been largely overlooked as a source of potentially therapeutic cells. The stem cells reside in the crypts located at the base of the protruding villi, reproduce themselves, and repopulate the gut lining as differentiated cells are sloughed off into the lumen. Some studies have demonstrated that gut stem cells can be isolated and maintained in culture, but the field is currently hampered by the lack of clear markers for these cells. Nevertheless, the relative accessibility of the cells and the similar pathways of differentiation of both intestinal and pancreatic endocrine cells make the gut an attractive potential source of cells to treat diabetes. In particular, it may be possible to recapitulate islet development by the introduction of specific factors to gut stem cells. Alternatively, gut endocrine cells might be coaxed to produce insulin and secrete it into the blood in a meal-responsive manner. Several investigations support the feasibility of both approaches as novel potential therapies for diabetes. Utilizing a patient's own gut cells to re-establish endogenous meal-regulated insulin secretion could represent an attractive approach to ultimately cure diabetes.

PMA induces the MUC5AC respiratory mucin in human bronchial epithelial cells, via PKC, EGF/TGF-alpha, Ras/Raf, MEK, ERK and Sp1-dependent mechanisms

Asthma and chronic obstructive pulmonary disease are highly prevalent and economically important inflammatory airway diseases associated with mucus hypersecretion. Considerable additional morbidity and mortality are related to acute exacerbations, which are associated with further mucus hypersecretion. MUC5AC is a prominent airway mucin; however, the signalling pathways regulating MUC5AC hypersecretion are not fully characterised. We investigated the signalling pathway regulating phorbol 12-myristate 13-acetate (PMA)-induced MUC5AC gene and protein expression in human respiratory epithelial cells. Using NCI-H292 cells, we demonstrated that treatment with PMA increased production of total and MUC5AC-specific mucin proteins. This increase was dependent on de novo MUC5AC gene transcription. We identified a short, proximal region of the MUC5AC promoter essential for this activity containing three specificity protein (Sp) 1 transcription factor-binding sites and a single CACCC site. By chemical inhibition, site-directed promoter mutagenesis and electrophoretic mobility-shift assay (EMSA), we demonstrated that PMA induced proteins binding to all three Sp1 sites and that they were all required for full induction of MUC5AC promoter activity. We then demonstrated a Ras-Raf-MEK/ERK signalling pathway was exclusively activated upstream of Sp1 activating the promoter and confirmed the requirement for matrix metalloproteinase activation leading to a ligand-dependent activation of the epidermal growth factor receptor. Finally, we demonstrated that activation of the novel protein kinase C isoforms delta and theta; was required upstream of the metalloproteinase activation. We have characterised a signalling pathway regulating PMA induction of MUC5AC. Studies such as this identify key signalling intermediates as targets for pharmacological intervention to treat mucus hypersecretion.

Osteopontin expression in particle-induced lung disease

Osteopontin (OPN) is a secreted cytokine with cell adhesive and chemoattractive functions whose expression is induced by a variety of environmental toxicants. It has been implicated in the pathogenesis of several pulmonary granulomatous and fibrotic conditions. For these reasons the authors investigated OPN expression in experimental particle-induced lung disease using a titanium dioxide exposure model in the rat. Under exposure conditions that resulted in fibroproliferative lung disease, rats had significant increases in total lung OPN mRNA expression and increased levels of OPN protein in bronchoalveolar lavage fluid (BALF) prior to the development of lesions. OPN immunoreactivity studies of lesion development provide evidence that this multifunctional cytokine may be important in the pathogenesis of particle-induced lung disease. Findings suggest that OPN may serve as an important biomarker for particle-induced lung disease.

Hypersensitivity to ovalbumin induces chronic intestinal dysmotility and increases the number of intestinal mast cells

Undiagnosed food allergies have been proposed as possible causes of promoting and perpetuating irritable bowel syndrome . Our aim was to find out if sensitization could induce chronic functional motor disturbances in the intestine and the mechanisms implicated. Rats were sensitized to ovalbumin (OVA) following three hypersensitivity induction protocols, two parenteral and one oral. Rat mast cell protease II (RMCP II) release in response to OVA challenge and immunoglobulin E (IgE) concentration were measured in serum. At least 1 week after challenge, small intestinal motility was evaluated using strain gauges. Intestinal tissue samples from orally sensitized rats were checked for in vitro stimulation with OVA. Mucosal mast cells were counted from duodenum sections. All sensitized rats showed intestinal hypermotility. Only rats sensitized by parenteral procedure showed an increase in RMCP II after OVA challenge in serum. IgEs increased only in the Bordetella pertussis sensitized group. Small intestine sections from orally sensitized rats released more RMCP II than sections from control rats. All sensitized rats showed an increase in the number of mucosal mast cells in duodenum. In conclusion, hypersensitivity to food proteins induces chronic motor alteration that persists long after antigen challenge and an excited/activated state of sensitized mucosal mast cells.

Teduglutide ([Gly2]GLP-2) protects small intestinal stem cells from radiation damage

Glucagon-like peptide-2 and its dipeptidyl peptidase (DP-IV) resistant analogue teduglutide are trophic for the gastrointestinal epithelium. Exposure increases villus height and crypt size and results in increased overall intestinal weight. As these effects may be mediated through stimulation of the stem cell compartment, they may promote intestinal healing and act as potential anti-mucositis agents in patients undergoing cancer chemotherapy. A study was initiated to investigate the protective effects of teduglutide on the murine small intestinal epithelium following gamma-irradiation using the crypt microcolony assay as a measure of stem cell survival and functional competence. Teduglutide demonstrated intestinotrophic effects in both CD1 and BDF1 mouse strains. In BDF1 mice, subcutaneous injection of GLP-2 or teduglutide (0.2 mg/kg/day, b.i.d.) for 14 days increased intestinal weight by 28% and resulted in comparable increases in crypt size, villus height and area. Teduglutide given daily for 6 or 14 days prior to whole body, gamma-irradiation significantly increased crypt stem cell survival when compared with vehicle-treated controls. The mean levels of protection over a range of doses provided protection factors from 1.3 to 1.5. A protective effect was only observed when teduglutide was given before irradiation. These results suggest that teduglutide has the ability to modulate clonogenic stem cell survival in the small intestine and this may have a useful clinical application in the prevention of cancer therapy-induced mucositis.

Immunolocalisation of P2X and P2Y nucleotide receptors in the rat nasal mucosa

Purinoceptor subtypes were localised to various tissue types present within the nasal cavity of the rat, using immunohistochemical methods. P2X3 receptor immunoreactivity was localised in the primary olfactory neurones located both in the olfactory epithelium and vomeronasal organs (VNO) and also on subepithelial nerve fibres in the respiratory region. P2X5 receptor immunoreactivity was found in the squamous, respiratory and olfactory epithelial cells of the rat nasal mucosa. P2X7 receptor immunoreactivity was also expressed in epithelial cells and colocalised with caspase 9 (an apoptotic marker), suggesting an association with apoptosis and epithelial turnover. P2Y1 receptor immunoreactivity was found within the respiratory epithelium and submucosal glandular tissue. P2Y2 receptor immunoreactivity was localised to the mucus-secreting cells within the VNO. The possible functional roles of these receptors are discussed.

Colostrum protein concentrate enhances intestinal adaptation after massive small bowel resection in juvenile pigs

OBJECTIVES

Short bowel syndrome (SBS) usually results from the surgical removal of a large segment of small intestine. Patient outcome depends on the extent of intestinal resection and adaptation of the remaining intestine. We evaluated the impact of colostrum protein concentrate (CPC) on intestinal adaptation after massive small bowel resection in a porcine model of infant SBS.

METHODS

Four-week-old piglets underwent an approximate 75% small bowel resection (R, n = 23) or a control transection operation (C, n = 14). Postoperatively, animals from both groups received either pig chow (R = 6, C = 5), polymeric infant formula (R = 6, C = 3) or polymeric infant formula supplemented with CPC (R = 11, C = 6) for 8 weeks until sacrifice. Clinical outcome measures included weight gain and stool consistency. Morphologic measures were intestinal villus height and crypt depth. Functional outcome measure was mucosal disaccharidase activity.

RESULTS

Resected animals fed polymeric infant formula alone had reduced weight gain compared with controls fed the same diet (P < 0.005). Despite massive small bowel resection, animals fed pig chow or polymeric infant formula supplemented with CPC grew at an equivalent rate to controls fed polymeric infant formula alone. Resected animals supplemented with CPC had increased villus length and crypt depth in the jejunum (P < 0.001) and ileum (P < 0.001) compared with resected animals fed either pig chow or polymeric infant formula alone.

CONCLUSION

In an animal model of SBS, CPC supplementation of polymeric infant formula resulted in normal weight gain and features of enhanced morphologic adaptation.

Effect of glucagon-like peptide-2 (GLP-2) on diurnal SGLT1 expression

Glucagon-like peptide 2 (GLP-2) is a 33-amino acid gut peptide that leads to villus hyperplasia and altered gene expression. We examined the effect of chronically administered GLP-2 on diurnal gene expression rhythms using the Na+/glucose cotransporter 1 (SGLT1) as the index. Animals were treated with [Gly2]GLP-2 (twice daily; 1microg/g body weight) or vehicle (control) for 10 days. Rats were killed at either 3 hr or 9 hr after light onset (ZT3 and ZT9, respectively), an interval during which SGLT1 expression exhibits a robust induction. SGLT1 mRNA expression was assessed by Northern blotting and in situ hybridization. SGLT1 protein was examined by immunofluorescence and Western blotting. Tissues from GLP-2-treated rats had increased villus height, crypt depth, and proliferation index (P < 0.05). GLP-2 administration did not alter the diurnal increase in mRNA levels of SGLT1, GLUT2, or GLUT5. However, in GLP-2-treated rats, the SGLT1 protein amount increased at both ZT3 and ZT9. Moreover, SGLT1 was preferentially localized to the apical membranes in this group. GLP-2 does not adversely affect the diurnal expression rhythm of SGLT1 and appears to increase membrane expression of the protein. These biological actions of GLP-2 may contribute to its therapeutic value in intestinal diseases.

Direct and indirect mechanisms regulating secretion of glucagon-like peptide-1 and glucagon-like peptide-2

The proglucagon-derived peptide family consists of three highly related peptides, glucagon and the glucagon-like peptides GLP-1 and GLP-2. Although the biological activity of glucagon as a counter-regulatory hormone has been known for almost a century, studies conducted over the past decade have now also elucidated important roles for GLP-1 as an antidiabetic hormone, and for GLP-2 as a stimulator of intestinal growth. In contrast to pancreatic glucagon, the GLPs are synthesized in the intestinal epithelial L cells, where they are subject to the influences of luminal nutrients, as well as to a variety of neuroendocrine inputs. In this review, we will focus on the complex integrative mechanisms that regulate the secretion of these peptides from L cells, including both direct and indirect regulation by ingested nutrients.

Nucleotide-mediated mucin secretion from differentiated human bronchial epithelial cells

Most current cell-based models for examining the regulation of mucin secretion demonstrate low signal-to-noise ratios, making experimental manipulation and data interpretation difficult. Using adenosine triphosphate (ATP) as a mucin secretagogue, we have developed a model of agonist-induced mucin secretion in differentiated human bronchial epithelial cells. Mucin secretory signals were estimated using enzyme-linked lectin assay, and typical signals of 300-400% of baseline were observed in response to a 30-min exposure to ATP (100 microM). ATP and uridine triphosphate equipotently stimulated mucin secretion consistent with mediation via P2Y2 receptor activation. Suramin and AR-C118925XX, a competitive P2Y2 receptor antagonist, inhibited adenosine 5'-o-(3-thiotriphosphate) (ATP-gammaS)-induced mucin secretion. A selective Gq G-protein antagonist (GP-ANT)-2A completely abrogated ATP-gammaS-induced mucin secretion. Pertussis toxin and the G(i/o)-specific, GP-ANT-2, had no effect. The phospholipase C inhibitor, D609, and the protein kinase C inhibitor, calphostin C, substantially inhibited ATP-gammaS-induced mucin secretion. Phorbol myristate acetate also stimulated mucin secretion in a calphostin C-sensitive manner. ATP-gammaS-induced mucin secretion was inhibited by the Ca2+ chelator, 1,2-bis(o-aminophenoxy) ethane-N,N,N',N'-tetra-acetic acid tetra (acetoxymethyl) ester. Ionomycin and thapsigargin both stimulated mucin secretion. Our data are broadly consistent with known G-protein-coupling and downstream signaling events associated with the P2Y2 receptor. The exceptional signal-to-noise ratios obtained using this model have permitted clear evaluation of the involvement of these mechanisms in agonist-induced mucin secretion from differentiated human bronchial epithelial cells.

Intestinal rehabilitation and the short bowel syndrome: part 1

The management of patients with intestinal failure due to short bowel syndrome (SBS) is complex, requiring a comprehensive approach that frequently necessitates long-term, if not life-long, use of parenteral nutrition (PN). Despite tremendous advances in the provision of PN over the past three decades, which have allowed significant improvements in the survival and quality of life of these patients, this mode of nutritional support carries with it significant risks to the patient, is very costly and, ultimately, does not attempt to improve the function of the remaining bowel. Intestinal rehabilitation refers to the process of restoring enteral autonomy and, thus, allowing freedom from parenteral nutrition, usually by means of dietary, medical, and, occasionally, surgical strategies. While recent investigations have focused on the use of trophic substances to increase the absorptive function of the remaining gut, whether intestinal rehabilitation occurs as a consequence of enhanced bowel adaptation or is simply a result of an optimized, comprehensive approach to the care of these patients remains unclear. In Part 1 of this review, an overview of SBS and pathophysiological considerations related to the remaining bowel anatomy in these patients will be provided. Additionally, a review of intestinal adaptation and factors that may enhance the adaptive process, focusing on evidence derived from animal studies, will also be discussed. In Part 2, relevant data on the development of intestinal adaptation in studies involving humans will be reviewed as will the general management of SBS. Lastly, the potential benefits of a multidisciplinary intestinal rehabilitation program in the care of these patients will also be discussed.

Ca2+ dependency of 'Ca2+-independent' exocytosis in SPOC1 airway goblet cells

SPOC1 airway goblet cells secrete mucin in response to P2Y2 receptor agonists and to secretagogues, phorbol 12-myristate 13-acetate (PMA) and ionomycin, which mobilize elements of the phospholipase C pathway, PKC and Ca2+, respectively. Previous studies demonstrated that mucin secretion from SLO-permeabilized, EGTA-buffered SPOC1 cells was stimulated by PMA at low Ca2+ levels (< 0.1 microm), consistent with the notion that regulated exocytosis may occur by Ca2+-independent pathways. We tested the alternative hypothesis that PMA-induced mucin secretion is, in fact, a Ca2+-dependent process under the conditions of low bulk Ca2+, one that is permitted in the typical SLO-permeabilized cell model by the slow binding kinetics of EGTA. Both IP3 and elevated bulk Ca2+ activated mucin secretion in SPOC1 cells buffered by EGTA, suggesting that IP3 generates a local Ca2+ gradient in the vicinity of the secretory granules to the degree necessary to trigger exocytosis. BAPTA, which binds Ca2+ approximately 100-fold faster than EGTA, diminished IP3-induced mucin release over a range of concentrations by > or = 69%, yet maintained an essentially normal mucin secretory response to elevated bulk Ca2+ in permeabilized SPOC1 cells. BAPTA also diminished the mucin secretory response of permeabilized cells to PMA, relative to the EGTA-buffered control: at PMA below 30 nm, BAPTA abolished the secretory response, and at higher concentrations it was reduced significantly relative to the EGTA-buffered controls. PMA-induced secretion in EGTA was insensitive to heparin. These results suggest that Ca2+ is released locally during PMA-induced exocytosis, by an IP3-independent mechanism.

Uridine-5'-triphosphate and adenosine triphosphate gammaS induce mucin secretion via Ca2+-dependent pathways in human nasal epithelial cells

OBJECTIVES

Nucleotides such as adenosine triphosphate (ATP) and uridine-5'-triphosphate (UTP) play fundamental roles in the early stage of secretion in nasal epithelial cells via the P2Y receptor. In this study, we examined the expression pattern of P2Y subtypes and their functions on Ca2+ influx ([Ca2+]i) in normal human nasal epithelial (NHNE) cells. We also examined the effect of UTP (an agonist for P2Y2) and ATPgammaS (an agonist for P2Y11) on mucin secretion and mucin gene expression.

MATERIAL AND METHODS

The expression pattern of P2Y receptors and the mRNA levels of MUC5AC, MUC5B and MUC8 were examined after treatment with UTP and ATPgammaS by means of reverse transcriptase polymerase chain reaction. Mucin was quantified by an immunoblotting assay. We measured [Ca2+]i in NHNE cells using a double perfusion chamber.

RESULTS

Two uracil-sensitive receptors (P2Y2, P2Y4) and two adenine-selective receptors (P2Y1, P2Y11) were expressed in NHNE cells. UTP and ATPgammaS increased [Ca2+]i via caffeine-sensitive pathways, and these two agonists stimulated mucin secretion to a similar magnitude without their gene enhancement. In addition, the mucin stimulatory effects subsided when the intracellular Ca2+ was removed by 2-bis-(2-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester.

CONCLUSION

This study showed that P2Y2 and P2Y11 receptors were expressed in NHNE cells and that their agonists, UTP and ATPgammaS, act as secretogogues on mucin secretion via Ca2+-dependent pathways.

Secretory granule exocytosis

Regulated exocytosis of secretory granules or dense-core granules has been examined in many well-characterized cell types including neurons, neuroendocrine, endocrine, exocrine, and hemopoietic cells and also in other less well-studied cell types. Secretory granule exocytosis occurs through mechanisms with many aspects in common with synaptic vesicle exocytosis and most likely uses the same basic protein components. Despite the widespread expression and conservation of a core exocytotic machinery, many variations occur in the control of secretory granule exocytosis that are related to the specialized physiological role of particular cell types. In this review we describe the wide range of cell types in which regulated secretory granule exocytosis occurs and assess the evidence for the expression of the conserved fusion machinery in these cells. The signals that trigger and regulate exocytosis are reviewed. Aspects of the control of exocytosis that are specific for secretory granules compared with synaptic vesicles or for particular cell types are described and compared to define the range of accessory control mechanisms that exert their effects on the core exocytotic machinery.