Discovery of Prostamide F2α and Its Role in Inflammatory Pain and Dorsal Horn Nociceptive Neuron Hyperexcitability

It was suggested that endocannabinoids are metabolized by cyclooxygenase (COX)-2 in the spinal cord of rats with kaolin/λ-carrageenan-induced knee inflammation, and that this mechanism contributes to the analgesic effects of COX-2 inhibitors in this experimental model. We report the development of a specific method for the identification of endocannabinoid COX-2 metabolites, its application to measure the levels of these compounds in tissues, and the finding of prostamide F2α (PMF2α) in mice with knee inflammation. Whereas the levels of spinal endocannabinoids were not significantly altered by kaolin/λ-carrageenan-induced knee inflammation, those of the COX-2 metabolite of AEA, PMF2α, were strongly elevated. The formation of PMF2α was reduced by indomethacin (a non-selective COX inhibitor), NS-398 (a selective COX-2 inhibitor) and SC-560 (a selective COX-1 inhibitor). In healthy mice, spinal application of PMF2α increased the firing of nociceptive (NS) neurons, and correspondingly reduced the threshold of paw withdrawal latency (PWL). These effects were attenuated by the PMF2α receptor antagonist AGN211336, but not by the FP receptor antagonist AL8810. Also prostaglandin F2α increased NS neuron firing and reduced the threshold of PWL in healthy mice, and these effects were antagonized by AL8810, and not by AGN211336. In mice with kaolin/λ-carrageenan-induced knee inflammation, AGN211336, but not AL8810, reduced the inflammation-induced NS neuron firing and reduction of PWL. These findings suggest that inflammation-induced, and prostanoid-mediated, enhancement of dorsal horn NS neuron firing stimulates the production of spinal PMF2α, which in turn contributes to further NS neuron firing and pain transmission by activating specific receptors

Sensitization of spinal cord nociceptive neurons with a conjugate of substance P and cholera toxin

<p>Abstract</p> <p>Background</p> <p>Several investigators have coupled toxins to neuropeptides for the purpose of lesioning specific neurons in the central nervous system. By producing deficits in function these toxin conjugates have yielded valuable information about the role of these cells. In an effort to specifically stimulate cells rather than kill them we have conjugated the neuropeptide substance P to the catalytic subunit of cholera toxin (SP-CTA). This conjugate should be taken up selectively by neurokinin receptor expressing neurons resulting in enhanced adenylate cyclase activity and neuronal firing.</p> <p>Results</p> <p>The conjugate SP-CTA stimulates adenylate cyclase in cultured cells that are transfected with either the NK1 or NK2 receptor, but not the NK3 receptor. We further demonstrate that intrathecal injection of SP-CTA in rats induces the phosphorylation of the transcription factor cyclic AMP response element binding protein (CREB) and also enhances the expression of the immediate early gene c-Fos. Behaviorally, low doses of SP-CTA (1 μg) injected intrathecally produce thermal hyperalgesia. At higher doses (10 μg) peripheral sensitivity is suppressed suggesting that descending inhibitory pathways may be activated by the SP-CTA induced sensitization of spinal cord neurons.</p> <p>Conclusion</p> <p>The finding that stimulation of adenylate cyclase in neurokinin receptor expressing neurons in the spinal cord produces thermal hyperalgesia is consistent with the known actions of these neurons. These data demonstrate that cholera toxin can be targeted to specific cell types by coupling the catalytic subunit to a peptide agonist for a g-protein coupled receptor. Furthermore, these results demonstrate that SP-CTA can be used as a tool to study sensitization of central neurons in vivo in the absence of an injury.</p

Tryptophan Prevents the Development of Non-Alcoholic Fatty Liver Disease

Roman Yanko,1,&ast; Mikhail Levashov,1,&ast; Olena Georgievna Chaka,1 Valentina Nosar,1 Sergey G Khasabov,2 Iryna Khasabova2,&ast; 1Department of Clinical Physiology of Connective Tissue, Bogomoletz Institute of Physiology National Academy of Sciences of Ukraine, Kiev, Ukraine; 2Department of Diagnostic and Biological Sciences, School of Dentistry, University of Minnesota, Minneapolis, MN, USA&ast;These authors contributed equally to this workCorrespondence: Roman Yanko, Department of Clinical Physiology of Connective Tissue, Bogomoletz Institute of Physiology National Academy of Sciences of Ukraine, Bogomoletz Street 4, Kiev, 01024, Ukraine, Tel +380442562477, Email [email protected]: The main aim of this research is to study the protective effects of tryptophan on the histomorphological and biochemical abnormalities in the liver caused by a high-calorie diet (HCD), as well as its ability to normalize mitochondrial functions in order to prevent the development of non-alcoholic fatty liver disease (NAFLD).Methods: The study was conducted in male Wistar rats aged 3 months at the start of the experiment. Control animals (group I) were fed a standard diet. Group II experimental animals were fed a diet with an excess of fat (45%) and carbohydrates (31%) for 12 weeks. Group III experimental animals also received L-tryptophan at a dose of 80 mg/kg body weight in addition to the HCD. The presence of NAFLD, functional activity, physiological regeneration, and the state of the liver parenchyma and connective tissue were assessed using physiological, morphological, histo-morphometric, biochemical, and biophysical research methods.Results: HCD induced the development of NAFLD, which is characterized by an increase in liver weight, hypertrophy of hepatocytes and an increase in the concentration of lipids, cholesterol and triglycerides in liver tissue. Increased alanine aminotransferase activity in the liver of obese rats also confirm hepatocytes damage. Tryptophan added to the diet lowered the severity of NAFLD by reducing fat accumulation and violations of bioelectric properties, and prevented a decrease in mitochondrial ATP synthesis.Conclusion: The addition of tryptophan can have a potential positive effect on the liver, reducing the severity of structural, biochemical, mitochondrial and bioelectric damage caused by HCD.Keywords: fatty liver disease, essential amino acids, obesit

Irritable bowel syndrome and dysphagia

Functional gastrointestinal disorders constitute a set of gastrointestinal disorders with absence of obvious organic and physiological dysfunctions observed in clinical routine examinations. The functional disorders are divided into many subclasses, e.g., functional esophageal disorders and functional bowel disorders. The diagnoses are set when the patients fulfil the Rome IV criteria after a careful anamnestic history and exclusion of organic diseases in appropriate investigations. The disorders have a high prevalence in the population worldwide, but are of a benign nature. The etiology and pathophysiology are unknown, but environmental factors, genetics, and psychosocial factors seem to be of importance. Visceral hypersensitivity and hyperalgesia are found. There is a great comorbidity between different functional gastrointestinal disorders, and between these disorders and other chronic pain syndromes characterized by central hypersensitivity, which are all included in the term somatic symptom disorder. The most common of the functional bowel disorders is irritable bowel syndrome (IBS), characterized by abdominal pain in association with altered bowel habits. Functional esophageal disorders represent functional chest pain, functional heartburn, reflux hypersensitivity, globus, and functional dysphagia. The most important in the treatment of these conditions are confirmation and reassurance of the symptoms and their benign nature. Dietary advices and symptomatic drug treatment against specific symptoms are the first line of prescription. If these interventions do not improve symptoms, prescription of antidepressants and psychological and behavioral therapy are recommended