Translation of Experimental Findings from Animal to Human Biology: Identification of Neuronal Mineralocorticoid and Glucocorticoid Receptors in a Sectioned Main Nerve Trunk of the Leg.

The activation of the mineralocorticoid (MR) and glucocorticoid (GR) receptors on peripheral sensory neurons seems to modify pain perception through both direct non-genomic and indirect genomic pathways. These distinct subpopulations of sensory neurons are not known for peripheral human nerves. Therefore, we examined MR and GR on subpopulations of sensory neurons in sectioned human and rat peripheral nerves.

Identification of glucocorticoid receptors as potential modulators of parasympathetic and sympathetic neurons within rat intracardiac ganglia.

Background: Emerging evidences indicate that glucocorticoid receptors (GR) play a regulatory role in cardiac function, particularly with regard to the autonomic nervous system. Therefore, this study aimed to demonstrate the expression and the precise anatomical location of GR in relation to the parasympathetic and sympathetic innervations of the heart.

Methods: The present study used tissue samples from rat heart atria to perform conventional reverse-transcriptase polymerase chain reaction (RT-PCR), Western blot, and double immunofluorescence confocal analysis of GR with the neuronal markers vesicular acetylcholine transporter (VAChT), tyrosine hydroxylase (TH), calcitonin gene-related peptide (CGRP) as well as the mineralocorticoid receptor (MR).

Naltrexone-Induced Cardiac Function Improvement is Associated With an Attenuated Inflammatory Response and Lipid Perioxidation in Volume Overloaded Rats.

In previous studies, upregulation of myocardial opioid receptors as well as the precursors of their endogenous ligands were detected in the failing heart due to chronic volume overload. Moreover, opioid receptor blockade by naltrexone improved left ventricular function. In parallel, inflammatory processes through cytokines have been confirmed to play an important role in the pathogenesis of different forms of heart failure.

Superior control of inflammatory pain by corticotropin-releasing factor receptor 1 via opioid peptides in distinct pain-relevant brain areas.

Background: Under inflammatory conditions, the activation of corticotropin-releasing factor (CRF) receptor has been shown to inhibit pain through opioid peptide release from immune cells or neurons. CRF's effects on human and animal pain modulation depend, however, on the distribution of its receptor subtypes 1 and 2 (CRF-R1 and CRF-R2) along the neuraxis of pain transmission. The objective of this study is to investigate the respective role of each CRF receptor subtype on centrally administered CRF-induced antinociception during inflammatory pain.

Identification of Mineralocorticoid Receptors, Aldosterone, and Its Processing Enzyme CYP11B2 on Parasympathetic and Sympathetic Neurons in Rat Intracardiac Ganglia.

Recent interest has focused on the mineralocorticoid receptor (MR) and its impact on the myocardium and the performance of the heart. However, there is a lack of evidence about MR expression and its endogenous ligand aldosterone synthesis with specific regard to the intrinsic cardiac nervous system. Therefore, we looked for evidence of MR and aldosterone in sympathetic and parasympathetic neurons of intracardiac ganglia.

Functional and Anatomical Characterization of Corticotropin-Releasing Factor Receptor Subtypes of the Rat Spinal Cord Involved in Somatic Pain Relief.

Corticotropin-releasing factor (CRF) orchestrates our body's response to stressful stimuli. Pain is often stressful and counterbalanced by activation of CRF receptors along the nociceptive pathway, although the involvement of the CRF receptor subtypes 1 and/or 2 (CRF-R1 and CRF-R2, respectively) in CRF-induced analgesia remains controversial. Thus, the aim of the present study was to examine CRF-R1 and CRF-R2 expression within the spinal cord of rats with Freund's complete adjuvant-induced unilateral inflammation of the hind paw using reverse transcriptase polymerase chain reaction, Western blot, radioligand binding, and immunofluorescence confocal analysis.

Chronic Naltrexone Therapy Is Associated with Improved Cardiac Function in Volume Overloaded Rats.

Purpose: Myocardial opioid receptors were demonstrated in animals and humans and seem to colocalize with membranous and sarcolemmal calcium channels of the excitation-contraction coupling in the left ventricle (LV). Therefore, this study investigated whether blockade of the cardiac opioid system by naltrexone would affect cardiac function and neurohumoral parameters in Wistar rats with volume overload-induced heart failure.

Methods: Volume overload in Wistar rats was induced by an aortocaval fistula (ACF).

Prostanoid Receptor Subtypes and Its Endogenous Ligands with Processing Enzymes within Various Types of Inflammatory Joint Diseases.

A complex inflammatory process mediated by proinflammatory cytokines and prostaglandins commonly occurs in the synovial tissue of patients with joint trauma (JT), osteoarthritis (OA), and rheumatoid arthritis (RA). This study systematically investigated the distinct expression profile of prostaglandin E2 (PGE2), its processing enzymes (COX-2), and microsomal PGES-1 (mPGES-1) as well as the corresponding prostanoid receptor subtypes (EP1-4) in representative samples of synovial tissue from these patients (JT, OA, and RA). Quantitative TaqMan®-PCR and double immunofluorescence confocal microscopy of synovial tissue determined the abundance and exact immune cell types expressing these target molecules.

Neuronal aldosterone elicits a distinct genomic response in pain signaling molecules contributing to inflammatory pain.

Background: Recently, mineralocorticoid receptors (MR) were identified in peripheral nociceptive neurons, and their acute antagonism was responsible for immediate and short-lasting (non-genomic) antinociceptive effects. The same neurons were shown to produce the endogenous ligand aldosterone by the enzyme aldosterone synthase.

Methods: Here, we investigate whether endogenous aldosterone contributes to inflammation-induced hyperalgesia via the distinct genomic regulation of specific pain signaling molecules in an animal model of Freund's complete adjuvant (FCA)-induced hindpaw inflammation.

Aldosterone Synthase in Peripheral Sensory Neurons Contributes to Mechanical Hypersensitivity during Local Inflammation in Rats.

Background: Recent emerging evidence suggests that extra-adrenal synthesis of aldosterone occurs (e.g., within the failing heart and in certain brain areas).

Efficacy-Based Perspective to Overcome Reduced Opioid Analgesia of Advanced Painful Diabetic Neuropathy in Rats.

Reduction of the opioid analgesia in diabetic neuropathic pain (DNP) results from μ-opioid receptor (MOR) reserve reduction. Herein, we examined the antinociceptive and antiallodynic actions of a novel opioid agonist 14--methymorphine-6--sulfate (14--MeM6SU), fentanyl and morphine in rats with streptozocin-evoked DNP of 9-12 weeks following their systemic administration. The antinociceptive dose-response curve of morphine but not of 14--MeM6SU or fentanyl showed a significant right-shift in diabetic compared to non-diabetic rats.

Identification of mineralocorticoid and glucocorticoid receptors on peripheral nociceptors: Translation of experimental findings from animal to human biology.

Evidence is accumulating that activation of mineralocorticoid (MR) and glucocorticoid (GR) receptors on peripheral sensory neurons modulates pain sensation. While the expression and exact anatomical localization of MR and GR in the various subpopulations of peripheral sensory neurons has been shown in animals, it is still unknown for the human skin. Therefore, we aimed to identify MR and GR mRNA and protein as well as the exact subpopulations of sensory neurons in human versus rat skin.

The Peripheral Versus Central Antinociception of a Novel Opioid Agonist: Acute Inflammatory Pain in Rats.

Opioid analgesics devoid of central side effects are unmet medical need in the treatment of acute pain (e.g. post-operative pain).

Pro- versus Antinociceptive Nongenomic Effects of Neuronal Mineralocorticoid versus Glucocorticoid Receptors during Rat Hind Paw Inflammation.

Background: In naive rats, corticosteroids activate neuronal membrane-bound glucocorticoid and mineralocorticoid receptors in spinal cord and periphery to modulate nociceptive behavior by nongenomic mechanisms. Here we investigated inflammation-induced changes in neuronal versus glial glucocorticoid and mineralocorticoid receptors and their ligand-mediated nongenomic impact on mechanical nociception in rats.

Methods: In Wistar rats (n = 5 to 7/group) with Freund's complete adjuvant hind paw inflammation, we examined glucocorticoid and mineralocorticoid receptor expression in spinal cord and peripheral sensory neurons versus glial using quantitative reverse transcription-polymerase chain reaction (qRT-PCR), Western blot, immunohistochemistry, and radioligand binding.

Accessibility of axonal G protein coupled mu-opioid receptors requires conceptual changes of axonal membrane targeting for pain modulation.

The mechanisms of axonal trafficking and membrane targeting are well established for sodium channels, which are the principle targets for perineurally applied local anaesthetics. However, they have not been thoroughly investigated for G protein coupled receptors such as mu-opioid receptors (MOR). Focusing on these axonal mechanisms, we found that axonal MOR functionality is quite distinct in two different pain states, i.

Pathological alterations in liver injury following congestive heart failure induced by volume overload in rats.

Heart failure has emerged as a disease with significant public health implications. Following progression of heart failure, heart and liver dysfunction are frequently combined in hospitalized patients leading to increased morbidity and mortality. Here, we investigated the underlying pathological alterations in liver injury following heart failure.

Histopathological Changes in the Kidney following Congestive Heart Failure by Volume Overload in Rats.

Background: This study investigated histopathological changes and apoptotic factors that may be involved in the renal damage caused by congestive heart failure in a rat model of infrarenal aortocaval fistula (ACF).

Methods: Heart failure was induced using a modified approach of ACF in male Wistar rats. Sham-operated controls and ACF rats were characterized by their morphometric and hemodynamic parameters and investigated for their histopathological, ultrastructural, and apoptotic factor changes in the kidney.

Comparative Expression Analyses of Pro- versus Anti-Inflammatory Mediators within Synovium of Patients with Joint Trauma, Osteoarthritis, and Rheumatoid Arthritis.

Synovial injury and healing are complex processes including catabolic effects by proinflammatory cytokines and anabolic processes by anti-inflammatory mediators. Here we examined the expression of pro- versus anti-inflammatory mediators in synovium of patients with diagnostic arthroscopy (control), joint trauma (JT), osteoarthritis (OA), and rheumatoid arthritis (RA). Synovial samples from these patients were subjected to RT-PCR and double immunofluorescence confocal microscopy of pro- and anti-inflammatory mediators as well as immune cell markers.

Membrane-bound glucocorticoid receptors on distinct nociceptive neurons as potential targets for pain control through rapid non-genomic effects.

Glucocorticoids were long believed to primarily function through cytosolic glucocorticoid receptor (GR) activation and subsequent classical genomic pathways. Recently, however, evidence has emerged that suggests the presence of rapid non-genomic GR-dependent signaling pathways within the brain, though their existence in spinal and peripheral nociceptive neurons remains elusive. In this paper, we aim to systemically identify GR within the spinal cord and periphery, to verify their putative membrane location and to characterize possible G protein coupling and pain modulating properties.

New Morphine Analogs Produce Peripheral Antinociception within a Certain Dose Range of Their Systemic Administration.

Growing data support peripheral opioid antinociceptive effects, particularly in inflammatory pain models. Here, we examined the antinociceptive effects of subcutaneously administered, recently synthesized 14-O-methylmorphine-6-O-sulfate (14-O-MeM6SU) compared with morphine-6-O-sulfate (M6SU) in a rat model of inflammatory pain induced by an injection of complete Freund's adjuvant and in a mouse model of visceral pain evoked by acetic acid. Subcutaneous doses of 14-O-MeM6SU and M6SU up to 126 and 547 nmol/kg, respectively, produced significant and subcutaneous or intraplantar naloxone methiodide (NAL-M)-reversible antinociception in inflamed paws compared with noninflamed paws.

Acute mechanical sensitization of peripheral nociceptors by aldosterone through non-genomic activation of membrane bound mineralocorticoid receptors in naive rats.

Recently, there is increasing interest in the role of peripheral mineralocorticoid receptors (MR) to modulate pain, but their localization in neurons and glia of the periphery and their distinct involvement in pain control remains elusive. In naive Wistar rats our double immunofluorescence confocal microscopy of the spinal cord, dorsal root ganglia, sciatic nerve and innervated skin revealed that MR predominantly colocalized with calcitonin-gene-related peptide (CGRP)- and trkA-immunoreactive (IR) nociceptive neurons and only marginally with myelinated trkB-IR mechanoreceptive and trkC-IR proprioreceptive neurons underscoring a pivotal role for MR in the modulation of pain. MR could not be detected in Schwann cells, satellite cells, and astrocytes and only scarcely in spinal microglia cells excluding a relevant functional role of glia-derived MR at least in naïve rats.

Protein kinase C-mediated mu-opioid receptor phosphorylation and desensitization in rats, and its prevention during early diabetes.

Painful diabetic neuropathy is associated with impaired opioid analgesia; however, the precise mechanism in sensory neurons remains unclear. This study aimed to identify putative mechanisms involved in modified opioid responsiveness during early streptozotocin-induced diabetes in rats. In this study, we demonstrate that in diabetic animals, impaired peripheral opioid analgesia is associated with a reduction in functional mu-opioid receptor (MOR) G protein coupling.

Evidence for MOR on cell membrane, sarcoplasmatic reticulum and mitochondria in left ventricular myocardium in rats.

Cardiac function is one important determinant to maintain tissue oxygenation and is thus highly regulated. In this context, it is interesting that centrally mediated opioidergic influence on cardiac function has long been known. Only recently, KOR and DOR have been found to be expressed in healthy left ventricular myocardium in rats and colocalized with parts of the excitation-contraction-coupling system.

Upregulation of the kappa opioidergic system in left ventricular rat myocardium in response to volume overload: Adaptive changes of the cardiac kappa opioid system in heart failure.

Opioids have long been known for their analgesic effects and are therefore widely used in anesthesia and intensive care medicine. However, in the last decade research has focused on the opioidergic influence on cardiovascular function. This project thus aimed to detect the precise cellular localization of kappa opioid receptors (KOR) in left ventricular cardiomyocytes and to investigate putative changes in KOR and its endogenous ligand precursor peptide prodynorphin (PDYN) in response to heart failure.

Cellular localization and adaptive changes of the cardiac delta opioid receptor system in an experimental model of heart failure in rats.

The role of the cardiac opioid system in congestive heart failure (CHF) is not fully understood. Therefore, this project investigated the cellular localization of delta opioid receptors (DOR) in left ventricle (LV) myocardium and adaptive changes in DOR and its endogenous ligand, the precursor peptide proenkephalin (PENK), during CHF. Following IRB approval, DOR localization was determined by radioligand binding using [H(3)]Naltrindole and by double immunofluorescence confocal analysis in the LV of male Wistar rats.