Anti-inflammatory activity of amylin and CGRP in different experimental models of inflammation

AMPK/MTOR/TP53 Signaling Pathway Regulation by Calcitonin Gene-Related Peptide Reduces Oxygen-Induced Lung Damage in Neonatal Rats through Autophagy Promotion

Our previous studies indicated that calcitonin gene-related peptide (CGRP) alleviates hyperoxia-induced lung injury and suggested the possible involvement of autophagy in this process. Herein, we aimed to further explore the potential involvement of tumor protein p53 (TP53) and autophagy in the mode of action of CGRP against hyperoxia-induced lung injury in vitro and in vivo. The study conducted tests on type II alveolar epithelial cells (AECII) and rats that were subjected to hyperoxia treatment or combined treatment of hyperoxia with CGRP, CGRP inhibitor, rapamycin (an autophagy agonist), 3-methyladenine (3-MA, an autophagy inhibitor), TP53 silencing/inhibitor (pifithrin-α), or expression vector/activator (PRIMA-1 (2,2-bis(hydroxymethyl)-3-quinuclidinone)) and their corresponding controls. We found that oxidative stress, apoptosis, and autophagy were all increased by hyperoxia treatment in vitro. However, treating AECII cells with CGRP reversed hyperoxia-induced oxidative stress and apoptosis but further promoted autophagy. In addition, the combined treatment with rapamycin or TP53 silencing with CGRP promoted the effect of CGRP, while contrary results were obtained with combined therapy with 3-MA or TP53 overexpression. In vivo, the number of hyperoxia-induced autophagosomes was promoted in the lung tissue of neonatal rats. Furthermore, hyperoxia increased the expression levels of AMP-activated protein kinase (AMPK) alpha 1 (also known as protein kinase AMP-activated catalytic subunit alpha 1 (PRKAA1)) but inhibited TP53 and mechanistic target of rapamycin (MTOR); these expression trends were regulated by CGRP treatment. In conclusion, we showed that CGRP can attenuate hyperoxia-induced lung injury in neonatal rats by enhancing autophagy and regulating the TP53/AMPK/MTOR crosstalk axis.

Regulation of Cutaneous Immunity In Vivo by Calcitonin Gene-Related Peptide Signaling through Endothelial Cells

Calcitonin gene-related peptide (CGRP) can bias the outcome of Ag presentation to responsive T cells in vitro away from Th1-type immunity and toward the Th2 and Th17 poles through actions on endothelial cells (ECs). To test the in vivo significance of this observation, we engineered a mouse lacking functional CGRP receptors on ECs (EC receptor activity modifying protein 1 [RAMP1] knockout mice). On percutaneous immunization to 1-fluoro-2,4-dinitrobenzene, stimulated CD4+ T cells from draining lymph nodes showed significantly reduced IL-17A expression with significantly increased IFN-γ, IL-4, and IL-22 expression at the protein and mRNA levels compared with control mice. Retinoic acid receptor-related orphan receptor γ t mRNA was significantly reduced, while mRNAs for T-box expressed in T cells and GATA binding protein 3 were significantly increased. In addition, EC RAMP1 knockout mice had significantly reduced contact hypersensitivity responses, and systemic administration of a CGRP receptor antagonist similarly inhibited contact hypersensitivity in wild-type mice. These observations provide compelling evidence that CGRP is a key regulator of cutaneous immunity through effects on ECs and suggest a novel pathway for potential therapeutic manipulation.

Serum level of Adrenomedullin in patients with primary knee osteoarthritis; relation to disease severity

Background

Adrenomedullin (AM) is a peptide which was suggested to be involved in the pathogenesis of osteoarthritis through its anti-inflammatory and anti-apoptotic effect. AM was found to be elevated in some inflammatory rheumatic diseases as rheumatoid arthritis and ankylosing spondylitis.

The current study was performed to measure serum Adrenomodullin (AM) concentrations in patients with primary knee osteoarthritis (KOA) and to assess association with severity of the disease. The study was performed on 50 patients with primary KOA diagnosed according to American College of Rheumatology (ACR) Revised Criteria for Early Diagnosis of Knee Osteoarthritis and 20 age- and sex-matched controls with no clinical features of KOA. The Kellgren and Lawrence (KL) classification was used to evaluate the disease severity of knee OA. Disease activity was assessed by The Western Ontario and McMaster Universities Arthritis Index (WOMAC). Blood samples had been collected from patients with OA and controls for assessing Adrenomodullin in patients’ sera by ELISA.

Results

There were a significant increase in serum Adrenomedullin concentrations in KOA patients compared to controls (10.64 ±19.2 ng/ml vs. 1.39 ±1.6 ng/ml in cases and controls respectively) (p value = 0.036). There was positive significant correlation of serum Adrenomedullin levels with KL grades (r=0.608, p value <0.001). OA patients with VAS score >6 have significantly higher serum Adrenomedullin levels than OA patients with VAS Score <6. No detected significant correlation between any of (patients’ age, BMI, disease duration, tenderness score, and WOMAC score) with serum Adrenomedullin levels among studied OA cases (p values >0.05).

Conclusion

This study concluded that serum Adrenomedullin (AM) level is elevated in patients with KOA and is positively correlated with the severity of disease.

Neuroprotective Effects of the Amylin Analog, Pramlintide, on Alzheimer's Disease Are Associated with Oxidative Stress Regulation Mechanisms

Administration of the recombinant analog of the pancreatic amyloid amylin, Pramlintide, has shown therapeutic benefits in aging and Alzheimer's disease (AD) models, both on cognition and amyloid-β (Aβ) pathology. However, the neuroprotective mechanisms underlying the benefits of Pramlintide remain unclear. Given the early and critical role of oxidative stress in AD pathogenesis and the known reactive oxygen species (ROS) modulating function of amyloids, we sought to determine whether Pramlintide's neuroprotective effects involve regulation of oxidative stress mechanisms. To address this, we treated APP/PS1 transgenic mice with Pramlintide for 3 months, starting at 5.5 months prior to widespread AD pathology onset, and measured cognition (Morris Water Maze), AD pathology, and oxidative stress-related markers and enzymes in vivo. In vitro, we determined the ability of Pramlintide to modulate H2O2-induced oxidative stress levels. Our data show that Pramlintide improved cognitive function, altered amyloid-processing enzymes, reduced plaque burden in the hippocampus, and regulated endogenous antioxidant enzymes (MnSOD and GPx1) and the stress marker HO-1 in a location specific manner. In vitro, Pramlintide treatment in neuronal models reduced H2O2-induced endogenous ROS production and lipid peroxidation in a dose-dependent manner. Together, these results indicate that Pramlintide's benefits on cognitive function and pathology may involve antioxidant-like properties of this compound.

Disruption of the Sensory System Affects Sterile Cutaneous Inflammation In Vivo

Increasing evidence suggests that nerve fibers responding to noxious stimuli (nociceptors) modulate immunity in a variety of tissues, including the skin. Yet, the role of nociceptors in regulating sterile cutaneous inflammation remains unexplored. To address this question, we have developed a detailed description of the sterile inflammation caused by overexposure to UVB irradiation (i.e., sunburn) in the mouse plantar skin. Using this model, we observed that chemical depletion of nociceptor terminals did not alter the early phase of the inflammatory response to UVB, but it caused a significant increase in the number of dendritic cells and αβ⁺ T cells as well as enhanced extravasation during the later stages of inflammation. Finally, we showed that such regulation was driven by the nociceptive neuropeptide calcitonin gene-related peptide. In conclusion, we propose that nociceptors not only play a crucial role in inflammation through avoidance reflexes and behaviors, but can also regulate sterile cutaneous immunity in vivo.

Amylin Treatment Reduces Neuroinflammation and Ameliorates Abnormal Patterns of Gene Expression in the Cerebral Cortex of an Alzheimer's Disease Mouse Model

Our recent study has demonstrated that peripheral amylin treatment reduces the amyloid pathology in the brain of Alzheimer's disease (AD) mouse models, and improves their learning and memory. We hypothesized that the beneficial effects of amylin for AD was beyond reducing the amyloids in the brain, and have now directly tested the actions of amylin on other aspects of AD pathogenesis, especially neuroinflammation. A 10-week course of peripheral amylin treatment significantly reduced levels of cerebral inflammation markers, Cd68 and Iba1, in amyloid precursor protein (APP) transgenic mice. Mechanistic studies indicated the protective effect of amylin required interaction with its cognate receptor because silencing the amylin receptor expression blocked the amylin effect on Cd68 in microglia. Using weighted gene co-expression network analysis, we discovered that amylin treatment influenced two gene modules linked with amyloid pathology: 1) a module related to proinflammation and transport/vesicle process that included a hub gene of Cd68, and 2) a module related to mitochondria function that included a hub gene of Atp5b. Amylin treatment restored the expression of most genes in the APP cortex toward levels observed in the wild-type (WT) cortex in these two modules including Cd68 and Atp5b. Using a human dataset, we found that the expression levels of Cd68 and Atp5b were significantly correlated with the neurofibrillary tangle burden in the AD brain and with their cognition. These data suggest that amylin acts on the pathological cascade in animal models of AD, and further supports the therapeutic potential of amylin-type peptides for AD.

Amylin and its G-protein-coupled receptor: A probable pathological process and drug target for Alzheimer's disease

G-protein-coupled receptors (GPCRs) are shown to be involved in Alzheimer's disease (AD) pathogenesis. However, because GPCRs include a large family of membrane receptors, it is unclear which specific GPCR or pathway with rational ligands can become effective therapeutic targets for AD. Amylin receptor (AmR) is a GPCR that mediates several activities, such as improving glucose metabolism, relaxing cerebrovascular structure, modulating inflammatory reactions and potentially enhancing neural regeneration. Recent studies show that peripheral treatments with amylin or its clinical analog, pramlintide, reduced several components of AD pathology, including amyloid plaques, tauopathy, neuroinflammation and other components in the brain, corresponding with improved learning and memory in AD mouse models. Because amylin shares a similar secondary structure with amyloid-β peptide (Aβ), I propose that the AmR/GPCR pathway is disturbed by a large amount of Aβ in the AD brain, leading to tau phosphorylation, neuroinflammation and neuronal death in the pathological cascade. Amylin-type peptides, readily crossing the blood-brain barrier (BBB), are the rational ligands to enhance this GPCR pathway and may exhibit utility as novel therapeutic agents for treating AD.

Plasma amylin concentration in suckling goat neonates and its relationship with C-reactive protein, selected biochemical and hormonal indicators

Amylin is a recently discovered neuropeptide hormone that belongs to the calcitonin gene-related peptide family. It is co-secreted with insulin in response to feed intake. In goat kids, neonatal mortality and morbidity seems to be relatively higher than in other farm species. This high mortality and morbidity in goat kids may be associated with underdeveloped metabolism and immune system during the first week of life. The main objectives of this study were to determine amylin concentration and its relationship with some hormones, biochemical indicators and with a general inflammatory marker, CRP (C-reactive protein) in goat neonates. Blood samples were collected from 30 Saanen goat neonates at 20–35 days of age. Plasma amylin and other hormone concentrations were measured by ELISA, whereas serum biochemical indices were analysed by spectrophotometry. The mean values of plasma amylin concentrations were 9.07 ± 0.25 pmol/l. Plasma amylin concentrations were positively correlated with plasma non-esterified fatty acids, CRP, prolactin, cortisol, insulin; however, a negative correlation was determined between plasma amylin and serum triglyceride concentrations. The current study suggests that amylin contents are strongly associated with circulating concentrations of some hormones and with those of CRP in Saanen goat kids.

Calcitonin gene-related peptide: key regulator of cutaneous immunity

Calcitonin gene-related peptide (CGRP) has been viewed as a neuropeptide and vasodilator. However, CGRP is more appropriately thought of as a pleiotropic signalling molecule. Indeed, CGRP has key regulatory functions on immune and inflammatory processes within the skin. CGRP-containing nerves are intimately associated with epidermal Langerhans cells (LCs), and CGRP has profound regulatory effects on Langerhans cell antigen-presenting capability. When LCs are exposed to CGRP in vitro, their ability to present antigen for in vivo priming of naïve mice or elicitation of delayed-type hypersensitivity is inhibited in at least some situations. Administration of CGRP intradermally inhibits acquisition of immunity to Th1-dominant haptens applied to the injected site while augmenting immunity to Th2-dominant haptens, although the cellular targets of activity in these experiments remain unclear. Although CGRP can be a pro-inflammatory agent, several studies have demonstrated that administration of CGRP can inhibit the elicitation of inflammation by inflammatory stimuli in vivo. In this regard, CGRP inhibits the release of certain chemokines by stimulated endothelial cells. This is likely to be physiologically relevant as cutaneous blood vessels are innervated by sensory nerves. Exciting new studies suggest a significant role for CGRP in the pathogenesis of psoriasis and, most strikingly, that CGRP inhibits the ability of LCs to transmit the human immunodeficiency virus 1 to T lymphocytes. A more complete understanding of the role of CGRP in the skin immune system may lead to new and novel approaches for the therapy of immune-mediated skin disorders.

Amylin and its analogs: a friend or foe for the treatment of Alzheimer's disease?

Amylin, a gut-brain axis hormone, and amyloid-beta peptides (Aβ), a major component of the Alzheimer's disease (AD) brain, share several features, including similar β-sheet secondary structures, binding to the same receptor and being degraded by the same protease, insulin degrading enzyme (IDE). However, while amylin readily crosses the blood brain barrier (BBB) and mediates several activities including improving glucose metabolism, relaxing cerebrovascular structure, modulating inflammatory reaction and perhaps enhancing neural regeneration, Aβ has no known physiological functions. Thus, abundant Aβ in the AD brain could block or interfere with the binding of amylin to its receptor and hinder its functions. Recent studies using animal models for AD demonstrate that amylin and its analog reduce the AD pathology in the brain and improve cognitive impairment in AD. Given that, in addition to amyloid plaques and neurofibrillary tangles, perturbed cerebral glucose metabolism and cerebrovascular damage are the hallmarks of the AD brain, we propose that giving exogenous amylin type peptides have the potential to become a new avenue for the diagnosis and therapeutic of AD. Although amylin's property of self-aggregation may be a limitation to developing it as a therapeutic for AD, its clinical analog, pramlintide containing 3 amino acid differences from amylin, does not aggregate like human amylin, but more potently mediates amylin's activities in the brain. Pramlintide is an effective drug for diabetes with a favorable profile of safety. Thus a randomized, double-blind, placebo-controlled clinical trial should be conducted to examine the efficacy of pramlintide for AD. This review summarizes the knowledge and findings on amylin type peptides and discuss pros and cons for their potential for AD.

Nerve-derived transmitters including peptides influence cutaneous immunology

Clinical observations suggest that the nervous and immune systems are closely related. For example, inflammatory skin disorders; such as psoriasis, atopic dermatitis, rosacea and acne; are widely believed to be exacerbated by stress. A growing body of research now suggests that neuropeptides and neurotransmitters serve as a link between these two systems. Neuropeptides and neurotransmitters are released by nerves innervating the skin to influence important actors of the immune system, such as Langerhans cells and mast cells, which are located within close anatomic proximity. Catecholamines and other sympathetic transmitters that are released in response to activation of the sympathetic nervous system are also able to reach the skin and affect immune cells. Neuropeptides appear to direct the outcome of Langerhans cell antigen presentation with regard to the subtypes of Th cells generated and neuropeptides induce the degranulation of mast cells, among other effects. Additionally, endothelial cells, which release many inflammatory mediators and express cell surface molecules that allow leukocytes to exit the bloodstream, appear to be regulated by certain neuropeptides and transmitters. This review focuses on the evidence that products of nerves have important regulatory activities on antigen presentation, mast cell function and endothelial cell biology. These activities are highly likely to have clinical and therapeutic relevance.

Diabetic neuropathy and heart failure: role of neuropeptides

Cardiovascular autonomic neuropathy (CAN), in which patients present with damage of autonomic nerve fibres, is one of the most common complications of diabetes. CAN leads to abnormalities in heart rate and vascular dynamics, which are features of diabetic heart failure. Dysregulated neurohormonal activation, an outcome of diabetic neuropathy, has a significant pathophysiological role in diabetes-associated cardiovascular disease. Key players in neurohormonal activation include cardioprotective neuropeptides and their receptors, such as substance P (SP), neuropeptide Y (NPY), calcitonin-gene-related peptide (CGRP), atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and C-type natriuretic peptide (CNP). These neuropeptides are released from the peripheral or autonomic nervous system and have vasoactive properties. They are further implicated in cardiomyocyte hypertrophy, calcium homeostasis, ischaemia-induced angiogenesis, protein kinase C signalling and the renin-angiotensin-aldosterone system. Therefore, dysregulation of the expression of neuropeptides or activation of the neuropeptide signalling pathways can negatively affect cardiac homeostasis. Targeting neuropeptides and their signalling pathways might thus serve as new therapeutic interventions in the treatment of heart failure associated with diabetes. This review discusses how neuropeptide dysregulation in diabetes might affect cardiac functions that contribute to the development of heart failure.

Calcitonin gene-related peptide inhibits chemokine production by human dermal microvascular endothelial cells

This study examined whether the sensory neuropeptide calcitonin gene-related peptide (CGRP) inhibits release of chemokines by dermal microvascular endothelial cells. Dermal blood vessels are associated with nerves containing CGRP, suggesting that CGRP-containing nerves may regulate cutaneous inflammation through effects on vessels. We examined CGRP effects on stimulated chemokine production by a human dermal microvascular endothelial cell line (HMEC-1) and primary human dermal microvascular endothelial cells (pHDMECs). HMEC-1 cells and pHDMECs expressed mRNA for components of the CGRP and adrenomedullin receptors and CGRP inhibited LPS-induced production of the chemokines CXCL8, CCL2, and CXCL1 by both HMEC-1 cells and pHDMECs. The receptor activity-modifying protein (RAMP)1/calcitonin receptor-like receptor (CL)-specific antagonists CGRP₈-₃₇ and BIBN4096BS, blocked this effect of CGRP in a dose-dependent manner. CGRP prevented LPS-induced IκBα degradation and NF-κB binding to the promoters of CXCL1, CXCL8 and CCL2 in HMEC-1 cells and Bay 11-7085, an inhibitor of NF-κB activation, suppressed LPS-induced production of CXCL1, CXCL8 and CCL2. Thus, the NF-κB pathway appears to be involved in CGRP-mediated suppression of chemokine production. Accordingly, CGRP treatment of LPS-stimulated HMEC-1 cells inhibited their ability to chemoattract human neutrophils and mononuclear cells. Elucidation of this pathway may suggest new avenues for therapeutic manipulation of cutaneous inflammation.

Amylin suppresses acetic acid-induced visceral pain and spinal c-fos expression in the mouse

Amylin is a member of calcitonin or calcitonin gene-related peptide (CGRP) family. Immunohistochemical study revealed a dense network of amylin-immunoreactive (irAMY) cell processes in the superficial dorsal horn of the mice. Numerous dorsal root ganglion (DRG) and trigeminal ganglion cells expressed moderate to strong irAMY. Reverse transcriptase-polymerase chain reaction (RT-PCR) revealed amylin receptor mRNA in the mouse spinal cord, brain stem, cortex, hypothalamus and hippocampus. The nociceptive or antinociceptive effects of amylin were evaluated in the acetic acid-induced writhing test. Amylin (0.1, 0.5 and 1 mg/kg, intraperitoneally (i.p.) or 1-10 microg, intrathecally (i.t.)) reduced the number of writhes in a dose-dependent manner. Pretreatment of the mice with the amylin receptor antagonist salmon calcitonin (8-32), either by i.p. or i.t., antagonized the effect of amylin on acetic acid-induced writhing test. Locomotor activity was not significantly modified by amylin injected either i.p. (0.01-1 mg/kg) or i.t. (1-10 microg). Measurement of c-fos mRNA by RT-PCR or proteins by Western blot showed that the levels were upregulated in the spinal cord of mice injected with acetic acid and the increase was attenuated by pretreatment with amylin (10 microg, i.t.). Collectively, our result demonstrates that irAMY is expressed in DRG neurons with their cell processes projecting to the superficial layers of the dorsal horn, and that the peptide by interacting with amylin receptors in the spinal cord may be antinociceptive.

Neuronal Control of Skin Function: The Skin as a Neuroimmunoendocrine Organ

This review focuses on the role of the peripheral nervous system in cutaneous biology and disease. During the last few years, a modern concept of an interactive network between cutaneous nerves, the neuroendocrine axis, and the immune system has been established. We learned that neurocutaneous interactions influence a variety of physiological and pathophysiological functions, including cell growth, immunity, inflammation, pruritus, and wound healing. This interaction is mediated by primary afferent as well as autonomic nerves, which release neuromediators and activate specific receptors on many target cells in the skin. A dense network of sensory nerves releases neuropeptides, thereby modulating inflammation, cell growth, and the immune responses in the skin. Neurotrophic factors, in addition to regulating nerve growth, participate in many properties of skin function. The skin expresses a variety of neurohormone receptors coupled to heterotrimeric G proteins that are tightly involved in skin homeostasis and inflammation. This neurohormone-receptor interaction is modulated by endopeptidases, which are able to terminate neuropeptide-induced inflammatory or immune responses. Neuronal proteinase-activated receptors or transient receptor potential ion channels are recently described receptors that may have been important in regulating neurogenic inflammation, pain, and pruritus. Together, a close multidirectional interaction between neuromediators, high-affinity receptors, and regulatory proteases is critically involved to maintain tissue integrity and regulate inflammatory responses in the skin. A deeper understanding of cutaneous neuroimmunoendocrinology may help to develop new strategies for the treatment of several skin diseases.

Central nervous system and other effects

Amylin enhanced the uptake of certain amino acids, crossed the blood-brain barrier, and increased body temperature. The physiological significance of these responses is currently unclear. An effect of peripherally injected amylin to enhance weakly trained memory fitted with similar effects of other gastrointestinal peptide hormones. Centrally administered amylin reduced locomotor and exploratory behavior. Amylin administered alone was analgesic when administered peripherally, via a non-opiate pathway. When administered in combination with opiates, there was an opiate-sparing synergy.

Amylin and the integrated control of nutrient influx

The most potent actions of amylin that occur at physiological plasma concentrations include inhibition of food intake, gastric emptying, acid and digestive enzyme secretion, and glucagon secretion. These actions share a common outcome; they each help regulate the rate at which nutrients (including glucose) appear in the blood (Ra). Amylin physiologically orchestrates, via several parallel processes, the rate of entry of nutrient into the circulation, as shown schematically in Fig. 1. In this way, amylin's function may be viewed as complementary to that of insulin (secreted from the same pancreatic beta-cells), which orchestrates the exit of nutrient from blood and its storage in peripheral tissues. The following discussion addresses the emerging picture that, although amylin is co-secreted with an endocrine hormone from endocrine tissue (the pancreatic islets), the target for its most potent and physiologically relevant effects appears to be the central nervous system. Amylin thus may be primarily regarded as a neuroendocrine hormone (Young et al., 2000).

Effect of the resection of the sciatic nerve on the Th1/Th2 balance in the synovia of the ankle joint of adjuvant arthritic rats

Inflamed synovia of the ankle joint after 2-4 weeks of adjuvant injection receives dense sensory innervation. To study the role of sensory nerves on the local inflammation, the relative expression of T helper 1 and 2 lymphocyte (Th1 and Th2) markers was investigated on both axotomized adjuvant arthritic (AA) rats, whose sciatic nerves were resected before adjuvant injection, and on sham-operated ones. Immunohistochemical expressions of CXC chemokine receptor 3 (CXCR3) and CC chemokine receptor 4 (CCR4) were examined and compared with those of Th1 cytokine (interferon-gamma, IFN-gamma), Th2 cytokine (interleukin-4, IL-4), and anti-T cell antibody (W3/25). Double-positive cells for IFN-gamma/CXCR3 and for IL-4/CCR4 were greater than 90% and greater than 95%, respectively. The reciprocal combinations, IL-4/CXCR3 and IFN-gamma/CCR4, however, yielded less than 10% and less than 5% of double-positive cells. CXCR3 and CCR4 thus appear to be available as markers for Th1/Th2 subsets in the synovia of AA rats. Using these markers, it became clear that the percentage of Th1 cells to total Th cells was higher than that of Th2 cells in axotomized AA rats at weeks 2-4, whereas in sham-operated AA rats, the percentage of Th1 cells to total Th cells was higher than that of Th2 cells at week 2 and the latter exceeded the former at week 4. Our observations strongly suggested the presence of the anti-inflammatory action of sensory nerves in rats with adjuvant arthritis.

Early immunoneutralization of calcitonin precursors attenuates the adverse physiologic response to sepsis in pigs

OBJECTIVE

The 116 amino acid prohormone procalcitonin and some of its component peptides (collectively termed calcitonin precursors) are important markers and mediators of sepsis. In this study, we sought to evaluate the effect of immunoneutralization of calcitonin precursors on metabolic and physiologic variables of sepsis in a porcine model.

DESIGN

A prospective, controlled animal study.

SETTING

A university research laboratory.

SUBJECTS

30-kg Yorkshire pigs.

INTERVENTIONS

Sepsis was induced in 15 pigs by intraperitoneal instillation of a suspension of cecal content (1 g/kg animal body weight) and a toxinogenic Escherichia coli solution (2 x 10(11) colony-forming units). During induction of sepsis, seven pigs received an intravenous infusion of purified rabbit antiserum, reactive to the aminoterminal portion of porcine prohormone procalcitonin. Another eight control pigs received an intravenous infusion of purified nonreactive rabbit antiserum. For all 15 animals, physiologic data (urine output, core temperature, arterial pressure, heart rate, cardiac index, and stroke volume index) and metabolic data (serum blood urea nitrogen and creatinine, arterial lactate, and pH) were collected or recorded hourly until death at 15 hrs.

MEASUREMENTS AND MAIN RESULTS

In this large-animal model of rapidly lethal peritonitis, serum calcitonin precursors were significantly elevated. Amino-prohormone procalcitonin-reactive antiserum administration resulted in a significant improvement or a beneficial trend in a majority of the measured physiologic and metabolic derangements induced by sepsis. Specifically, arterial pressure, cardiac index, stroke volume index, pH, and creatinine were all significantly improved, while urine output and serum lactate had beneficial trends. Treated animals also experienced a statistically significant increase of short-term survival.

CONCLUSIONS

These data from a large-animal model with polymicrobial sepsis demonstrate the salutary effect of early immunoneutralization of calcitonin precursors on physiologic and metabolic variables. Immunologic blockade of calcitonin precursors may offer a novel therapeutic approach to human sepsis.

Localization of functional calcitonin gene-related peptide binding sites in a subpopulation of cultured dorsal root ganglion neurons

In this study we investigated whether cultured dorsal root ganglion (DRG) neurons from the adult rat express binding sites for calcitonin gene-related peptide (CGRP). These were identified on fixed cells by using CGRP labeled at the N-terminal site with 1.4-nm gold particles. After 1 day in culture, about 20% of small to medium-sized DRG neurons showed CGRP-gold binding. Binding of CGRP-gold was dose-dependently reduced by coadministration of CGRP. The calcium imaging technique in living cells revealed that the bath administration of CGRP evoked an increase of the intracellular calcium in up to 30% of the DRG neurons tested. Both depletion of intracellular calcium stores by thapsigargin or using a calcium-free medium blocked the CGRP-mediated increase of cytosolic calcium in most neurons. Thus intracellular and extracellular sources of calcium are relevant for the CGRP response. Using the whole-cell patch-clamp technique, about 30% of the neurons were found to exhibit an inward current and a depolarization upon administration of CGRP close to the neurons. Immunocytochemical double-labeling techniques showed that most of the CGRP-gold binding sites were expressed in unmyelinated (neurofilament 200-negative) DRG neurons. Most of the neurons with CGRP-gold binding sites also expressed the tyrosine kinase A receptor, and all of them showed CGRP-like immunoreactivity. This study shows, therefore, that a subpopulation of unmyelinated, peptidergic primary afferent neurons express CGRP binding sites that can be activated by CGRP in an excitatory direction. The binding sites may serve as autoreceptors because all of these neurons also synthesize CGRP. The activation of CGRP binding sites may sensitize primary afferent neurons and influence the release of mediators.

Antiinflammatory activity of adrenomedullin in the acetic acid peritonitis in rats

The antiinflammatory effect of ADM was studied in different models of inflammation and compared to the one of CGRP. Peptides were active against acetic acid-induced peritonitis in the rats. ADM and CGRP exerted the antiinflammatory effect at different doses, 400 and 20 ng/kg respectively, but with different efficacy (ADM >CGRP). This effect was blocked by pretreatment with CGRP (8-37) fragment or with L-NAME. No antiinflammatory activity was evidenced against serotonin- or carrageenin-induced rat paw edema. Our data suggest that ADM exerts antiinflammatory activity in the model characterized by a vascular component. This effect involves CGRP receptors and appears to be mediated by nitric oxide system.

Vagally dependent protective action of calcitonin gene-related peptide on colitis

This work evaluates the mechanism of action of calcitonin gene-related peptide (CGRP) on colitis. Firstly, Wistar rats were intracolonically instilled with trinitrobenzenesulfonic acid (TNBS) and i.v. treated by either alphaCGRP, or hCGRP(8-37), or by vehicle. The inflammatory level was evaluated 8 h and 4 days after TNBS. Secondly, intracerebroventricular alphaCGRP was assessed on the 4-day group with colitis. Finally, i.v. alphaCGRP was administered in vagotomized animals, and tested on the 4-day group with colitis. Colitis was aggravated by hCGRP(8-37), and decreased by peripheral but not central alphaCGRP. AlphaCGRP was inactive on inflammatory parameters in vagotomized colitic rats. This suggests that endogenous peripheral CGRP has an anti-inflammatory role in TNBS-induced colitis, depending upon the integrity of the vagus.

Modulating effects of sensory and autonomic neuropeptides on murine splenocyte proliferation and cytokine secretion induced by Leishmania major

The intimate, bidirectional link between neuroendocrine and immune systems is now accepted. A modulating effect of the nervous system on immune and inflammatory responses has been corroborated by identification of neuropeptide receptors on immunocompetent cells and the finding that neuropeptides can regulate leukocyte functions. The present study was undertaken to investigate the possible immunomodulatory role of sensory (SOM, CGRP and SP) and autonomic (VIP and NPY) neuropeptides in a murine model of cutaneous leishmaniasis, using two genetically different inbred mouse strains, BALB/c and C57BL/6, respectively susceptible and resistant to Leishmania (L.) major infection. The parameters studied were extent of splenocyte proliferation, as measured by thymidine uptake, and the ability of these cells to secrete IFN-gamma and IL-4 by using a two-site ELISA, upon in vitro challenge with L. major parasites and addition of the neuropeptides. The resistant mouse splenocyte proliferation was enhanced by SOM, CGRP, and VIP at 10(-5), 10(-6) and 10(-9) M concentration, respectively, but was inhibited by NPY at 10(-5) M. Proliferation of the splenocytes from the susceptible strain was inhibited by SOM (10(-11) M) and CGRP(10(-5) M). Somatostatin, at various concentrations, stimulated IFN-gamma secretion in both mouse strain splenocytes, and IL-4 production in the susceptible mouse. Calcitonin gene-related peptide enhanced IFN-gamma secretion in susceptible mouse splenocytes at 10(-6), 10(-7) and 10(-9) M, as did VIP at 10(-10) M and NPY at 10(-7) M. Vasoactive intestinal peptide also stimulated IL-4 production in BALB/c splenocytes at all concentrations used. Substance P had no effect on either cell proliferation or cytokine secretion in either of the two mouse strains. These findings indicate that the nervous system, represented by sensory and autonomic nerve terminals and their content of neuromediators, may be involved in the pathophysiology of cutaneous leishmaniasis.

Pituitary adenylate cyclase-activating polypeptide and islet amyloid polypeptide in primary sensory neurons: functional implications from plasticity in expression on nerve injury and inflammation

Primary sensory neurons serve a dual role as afferent neurons, conveying sensory information from the periphery to the central nervous system, and as efferent effectors mediating, e.g., neurogenic inflammation. Neuropeptides are crucial for both these mechanisms in primary sensory neurons. In afferent functions, they act as messengers and modulators in addition to a principal transmitter; by release from peripheral terminals, they induce an efferent response, "neurogenic inflammation," which comprises vasodilatation, plasma extravasation, and recruitment of immune cells. In this article, we introduce two novel members of the sensory neuropeptide family: pituitary adenylate cyclase-activating polypeptide (PACAP) and islet amyloid polypeptide (IAPP). Whereas PACAP, a vasoactive intestinal polypeptide-resembling peptide, predominantly occurs in neuronal elements, IAPP, which is structurally related to calcitonin gene-related peptide, is most widely known as a pancreatic beta-cell peptide; as such, it has been recognized as a constituent of amyloid deposits in type 2 diabetes. In primary sensory neurons, under normal conditions, both peptides are predominantly expressed in small-sized nerve cell bodies, suggesting a role in nociception. On axotomy, the expression of PACAP is rapidly induced, whereas that of IAPP is reduced. Such a regulation of PACAP suggests that it serves a protective role during nerve injury, but that of IAPP may indicate that it is an excitatory messenger under normal conditions. In contrast, in localized adjuvant-induced inflammation, expression of both peptides is rapidly induced. For IAPP, studies in IAPP-deficient mice support the notion that IAPP is a pronociceptive peptide, because these mutant mice display a reduced nociceptive response when challenged with formalin.

Decreased concentrations of CGRP in Leishmania major murine cutaneous leishmaniasis

The expression of the sensory neuropeptide calcitonin gene-related peptide (CGRP) in the skin, secondary lymphoid organs and dorsal root ganglia (L4-L6) in Leishmania major-induced inflammation was evaluated by radioimmunoassay. The investigation was conducted on two mouse strains, the susceptible BALB/c and the resistant C57BL/6. The CGRP concentration in the inflamed skin of both mouse strains was decreased as early as 1 week postinfection, compared to controls. A further reduction was observed in both mouse strains throughout the 9-week study period, but was more evident in the susceptible strain. The CGRP concentration was increased in the ipsilateral dorsal root ganglia (L4-L6) of mice of the resistant strain 1 week postinfection, while no change was observed in the susceptible strain. In the remaining part of the study period there was a reduction in CGRP in the ipsilateral dorsal root ganglia of both mouse strains. In the spleen, a reduction was noted in the infected BALB/c at all measurement times (significant at 6 and 9 weeks), while no change was observed in C57BL/6 strain. These findings may indicate a regulatory function of CGRP in the pathophysiology of murine cutaneous leishmaniasis and hence in the disease outcome. The reduction in CGRP might also explain the defective nociception observed in patients with cutaneous leishmaniasis.

Islet amyloid polypeptide and calcitonin gene-related peptide expression are down-regulated in dorsal root ganglia upon sciatic nerve transection

Islet amyloid polypeptide (IAPP) is structurally related to calcitonin gene-related peptide (CGRP) and has been implicated in glucose homeostasis and diabetes pathogenesis because it is expressed in insulin cells and forms amyloid in pancreatic islets from type II diabetic patients. IAPP is also constitutively co-expressed with CGRP in rat sensory neurons. Whether expression of IAPP is altered by nerve injury with or without regeneration was investigated in adult rats subjected to unilateral sciatic axotomy; IAPP and CGRP expression were determined by quantitative in situ hybridization and immunocytochemistry at days 3, 10 and 30 after axotomy. In ipsilateral L4-L5 dorsal root ganglia (DRG), the percentages of nerve cell profiles labelled for IAPP and CGRP mRNA were reduced at all time points studied. IAPP and CGRP mRNA expression were lower in nerve cell profiles in ipsilateral DRGs compared to the contralateral side after axotomy alone whereas epineurial nerve suture maintained or restored IAPP and CGRP expression. The numbers of IAPP- and CGRP-immunoreactive DRG nerve cell profiles and dorsal horn fibers were reduced on the ipsilateral side at all time points. Thus, IAPP and CGRP expression are down-regulated upon axotomy. Nerve repair maintains or restores IAPP and CGRP expression in individual neurons but does not prevent the loss of CGRP/IAPP phenotype of some of these neurons in response to axotomy.