The effect of peripheral chronic salsolinol administration on fat pad adipocytes morphological parameters.

Salsolinol (1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline) is thought to regulate dopaminergic neurons and to act as a mediator in the neuroendocrine system. We have previously reported that exogenous salsolinol evokes enteric neuronal cell death, leading to the impairment of myenteric neurons density and abnormal intestinal transit in rats. We also observed significant reduction of body weight, related to the disrupted gastrointestinal homeostasis. e aim of current study was to evaluate the influence of prolonged salsolinol administration body weight, food intake, adipose tissue accumulation and fad pad adipocyte morphological parameters assessed by image analysis. Male Wistar rats were subjected to continuous intraperitoneal low dosing of salsolinol - 200 mg/kg in total with ALZET osmotic mini-pumps (Durtec, USA) for 2 or 4 weeks with either normal or high-fat diet. Appropriate groups served as the controls. Food intake, body weight were measured each morning. Both epididymal fat pads were dissected, weighted and processed for routine hematoxylin and eosin staining. e following parameters: cell area, perimeter, long and short axis, aspect ratio and circularity factor were assessed in stained specimens with the image analysis system (Multiscan, Poland). Salsolinol administration significantly reduced total body mass with no differences in total food intake between the groups. The epididymal fat pad weight over final body mass ratio was lower in salsolinol treated rats on high fat diet in comparison with the control groups. e area, perimeter, short and long axis of the fad pad adipocytes were significantly decreased in salsolinol treated animals in comparison with relevant controls. Salsolinol targets some regulatory mechanisms concerned with the basic rat metabolism. Prolonged peripheral salsolinol administration in rats significantly decreases the adipocyte size, and such effect is related to the weight loss and reduced adipose tissue accumulation.

The non-motor complications in Parkinson's disease - what can we learn from animal models?

Sporadic Parkinson's disease is a widespread human disease that has never been reported in non-human vertebrates. The etiopathogenesis of the non-motor symptoms in the disease is not well understood and it is difficult to interpret the roles of affected neurotransmitters in currently available animal models. Most of the non-motor symptoms do not correlate with the stage of motor deficits and precede the development of motor symptoms by many years, before the permanent loss of dopaminergic neurons in the basal ganglia. The aim of this review is to briefly summarize the advantages and limitations of the well-recognized mammalian animal models with special regard to the non-motor complications of the prodromal and early stage Parkinson's disease.

Electrical chronic vagus nerve stimulation activates the hypothalamic-pituitary-adrenal axis in rats fed high-fat diet.

OBJECTIVES: The brain and the gut communicate bi-directionally through the brain-gut axis. The key role in such interactions plays autonomic nervous system and its major component, the vagus nerve. There is growing evidence that vagus nerve stimulation (VNS) has a suppressive effect on both short- and long-term feeding in animal models. In the present study, we investigated the effect of VNS on the hypothalamic pituitary adrenal axis, feeding behavior and appetite in rats fed a high-fat diet. METHODS: Adult male Wistar rats were implanted with a microstimulator (MS) and fed a high-fat diet throughout the study (42 days). The left vagus nerve was stimulated subdiaphragmatically by electrical pulses (10 ms, 200 mV, 1 Hz or 10 Hz respectively, 12 h a day) generated by the MS. Daily food intake and body weight were measured. At the end of the experiment, animals were euthanized and serum corticosterone levels were assessed by immunoassays. Adipose tissue content was evaluated by measuring epididymal fat pads' weight. To determine whether VNS activated food-related areas of the brain, neuronal c-Fos induction in the nucleus of the solitary tract (NTS) was assessed. RESULTS: Chronic VNS decreased food intake, body weight gain and epididymal fat pad weight in stimulated animals compared to control animals. Serum corticosterone concentrations were significantly elevated following VNS, and neuronal responses in the NTS were observed. CONCLUSIONS: The study demonstrates that chronic electrical VNS exerts anorexigenic effects on food intake and body weight gain, and the hypothalamic pituitary adrenal axis activation may contribute to these effects.

Elevated interleukin-1ß serum level after chronic peripheral salsolinol administration.

The catechol isoquinoline derivatives are endogenous compounds present in the mammalian brain and the representative one is referred to as salsolinol. It may be formed from aromatic amines leading to neurotoxic N-methyltetrahydroquinolinium ions that may play a role in the etiology of Parkinson's disease (PD). Neuroinflammation and apoptosis is thought to be a major contributor to the neuronal degeneration in PD. The alteration of inflammatory cytokines in the brain, cerebral spinal fluid and plasma of PD patients supports the existence of functional interconnections between the immune and nervous systems. In animal studies, chronic administration of salsolinol induced parkinsonian-like symptoms, both peripherally and centrally. However, still little has been known about the effects of salsolinol on the pro-inflammatory cytokine production or mast cells activation in the gastrointestinal tract. Male Wistar rats were subjected to continuous intraperitoneal dosing of salsolinol (200 mg/kg in total) with osmotic mini-pumps for two or four weeks and fed with either standard or high fat diet. An equivalent group of rats served as the appropriate controls. At the end of the experiment animals were decapitated and blood samples as well as tissue fragments were collected. Serum samples were assayed immunoenzymatically for IL-11ß and by liquid chromatography-mass spectrometry for histamine. Tissue fragments from gastric antrum, duodenum and proximal colon were formalin fixed, paraffin-embedded and stained with either hematoxylin and eosin or toluidine blue. Once activated, mast cells might secrete a range of neurosensitizing and pro-inflammatory molecules, increasing gut-blood and blood-brain barrier permeability. Cytokines mediate the activity of immune cells and may affect brain neurochemistry. The results of the present work serve as an additional support for the existence of an interrelationship between the nervous and immune system.

MAP kinase phosphatase-2 plays a critical role in response to infection by Leishmania mexicana.

In this study we generated a novel dual specific phosphatase 4 (DUSP4) deletion mouse using a targeted deletion strategy in order to examine the role of MAP kinase phosphatase-2 (MKP-2) in immune responses. Lipopolysaccharide (LPS) induced a rapid, time and concentration-dependent increase in MKP-2 protein expression in bone marrow-derived macrophages from MKP-2(+/+) but not from MKP-2(-/-) mice. LPS-induced JNK and p38 MAP kinase phosphorylation was significantly increased and prolonged in MKP-2(-/-) macrophages whilst ERK phosphorylation was unaffected. MKP-2 deletion also potentiated LPS-stimulated induction of the inflammatory cytokines, IL-6, IL-12p40, TNF-α, and also COX-2 derived PGE(2) production. However surprisingly, in MKP-2(-/-) macrophages, there was a marked reduction in LPS or IFNγ-induced iNOS and nitric oxide release and enhanced basal expression of arginase-1, suggesting that MKP-2 may have an additional regulatory function significant in pathogen-mediated immunity. Indeed, following infection with the intracellular parasite Leishmania mexicana, MKP-2(-/-) mice displayed increased lesion size and parasite burden, and a significantly modified Th1/Th2 bias compared with wild-type counterparts. However, there was no intrinsic defect in MKP-2(-/-) T cell function as measured by anti-CD3 induced IFN-γ production. Rather, MKP-2(-/-) bone marrow-derived macrophages were found to be inherently more susceptible to infection with Leishmania mexicana, an effect reversed following treatment with the arginase inhibitor nor-NOHA. These findings show for the first time a role for MKP-2 in vivo and demonstrate that MKP-2 may be essential in orchestrating protection against intracellular infection at the level of the macrophage.

Chronic vagus nerve stimulation reduces body fat, blood cholesterol and triglyceride levels in rats fed a high-fat diet.

There is growing evidence that vagus nerve stimulation (VNS) exerts a suppressive effect on both short- and long-term feeding in animal models. We previously showed that VNS with high-frequency (10 Hz) electrical impulses decreased food intake and body weight in rats. In the present study, we investigated the effect of VNS with a low frequency (1 Hz) on the serum lipid concentrations, feeding behavior and appetite in rats fed a high-fat diet. The levels of appetite-regulating peptides were also assessed. Adult male Wistar rats were subcutaneously implanted with a microstimulator (MS) and fed a high-fat diet throughout the entire study period (42 days). The left vagus nerve was stimulated subdiaphragmatically by rectangular electrical pulses (10 ms, 200 mV, 1 Hz, 12 h a day) generated by the MS. The daily food intake and body weight were measured each morning. At the end of the experiments, the serum glucose, cholesterol, triglycerides, low-density lipoproteins, high-density lipoproteins, ghrelin, leptin and nesfatin-1 concentrations were measured. The adipose tissue content was evaluated by the assessment of the weight of the epididymal fat pads. Chronic VNS significantly decreased food intake, body weight gain and epididymal fat pad weight. VNS also lowered the total plasma cholesterol concentrations and triglyceride levels. Finally, the serum concentrations of nesfatin-1 were elevated, leptin levels were decreased, and ghrelin levels remained unchanged after VNS. The study demonstrates that chronic electrical VNS exerts anorexigenic effects, lowering the blood concentration of lipids. Increased nesfatin-1 levels may contribute to these effects.

The influence of salsolinol on basic rat metabolism.

Parkinson's disease (PD) is associated with a broad spectrum of non-motor symptoms, which are poorly understood and foremost, may precede motor impairment. These symptoms include weight changes and gastrointestinal dysregulation. In our experiment, we applied salsolinol given peripherally and continuously in rats to induce changes in the enteric nervous system, which might be similar to those observed in PD patients. Surprisingly, we noted decrease in body weight and alteration in body fat contents of the animals during salsolinol exposure. The blood glucose levels, lipid profile and hepatic enzymes levels were assessed as well. While lipid profile, postprandial blood glucose and hepatic enzymes levels remained indifferent, postprandial triglyceridemia was significantly lower in all salsolinol-treated rats in comparison with the control, which might be related to disturbed absorption. We also suggest that diminished body weight gain and lower adipose tissue accumulation in salsolinol-treated animals were due to delayed gastric emptying together with disturbed gut function resulting in absorptive dysfunction.

The effects of salsolinol on the mucosal mast cells in the rat gut.

Mast cells in the gastrointestinal tract have been found in close spatial contact with the regulatory cells of gastrointestinal motility: interstitial cells of Cajal (ICC) and myenteric neurons, suggesting their functional interaction. Because of the regulatory role of mast cells even the slight damage or change in activity of these cells may cause considerable disorder of the gut motility. The catechol isoquinoline derivatives are endogenous compounds present in the mammalian brain and the representative one is referred to as salsolinol. Increased salsolinol levels are detected in the cerebrospinal fluid of Parkinson's disease patients. Gastrointestinal dysmotility in those patients has been associated with peripheral action of salsolinol. The aim of this study was to evaluate effects of exogenous salsolinol on mast cells in the gastrointestinal tract of rats. Male Wistar rats (n = 8) were injected intraperitoneally with salsolinol (50 mg/kg/day) for 3 weeks and the equal group served as a control. On the last day the animals were sacrificed, stomachs, small and large intestines were removed, and paraffin embedded specimens were prepared. Slides were toluidine blue stained and the total number and percentage of degranulated mast cells in gastric antral, duodenal and ascending colon wall were assessed by image analysis. The number of mast cells in the gastrointestinal wall was decreased in the salsolinol group compared to the control--in the stomach 98.7 +/- 53.3 vs. 156.7 +/- 45.8, in the duodenum 2.6 +/- 2.1 vs. 7.83 +/- 7.8 and in colon 12.8 +/- 14 vs. 10.7 +/- 17.1 (salsolinol treated vs. control group). Carried out examinations showed the destructive action of salsolinol on the mast cells in all segments examined of gastrointestinal tract.

Intestinal mucosal mast cells and vagal nerve stimulation.

Vagal nerve stimulation, because of its involvement in the short- and long-term regulation of food intake, might become a useful tool in the treatment of obesity. However, both peripheral and central mechanisms of its action are still poorly understood. There is a strong evidence that intestinal mucosal mast cells play a general transduction role between the gastrointestinal tract and the central nervous system.

Neuropathic alterations of the myenteric plexus neurons following subacute intraperitoneal administration of salsolinol.

INTRODUCTION: Impairment of the enteric nervous system has been suggested to occur within the pathogenesis of neurodegenerative diseases. Thus, in the current study, we consider salsolinol (1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline, SAL) as a substance that can potentially induce myenteric neurodegen-eration. MATERIAL AND METHODS: Male Wistar rats were subjected to continuous intraperitoneal dosing of salsolinol (200 mg/kg in total) with osmotic mini-pumps for either two or four weeks. An equivalent group of rats served as the control. Jejunal myenteric neurons were subjected to immunofluorescence staining to detect neuron specific protein - protein gene product (pan-neuronal marker, PGP 9.5), nitric oxide synthase (NOS), choline acetyltransferase (ChAT), Bax-protein and alpha-synuclein. In search of any functional impairment within the gastrointestinal tract, gut motility was assessed by determining the residual solid food contents in the stomach and the small and large intestine transit. RESULTS: The myenteric neuron count, the mean size of the neuron body, the area of ganglia and the diameter of nerve strands were decreased in both of the salsolinol-treated groups compared with the controls. The number of NOS-positive cells was lower in the salsolinol-treated groups, while the number of ChAT-positive cells remained unchanged in comparison with the controls. Neurons expressing the pro-apoptotic Bax protein and alpha-synuclein deposits were observed among the myenteric neurons of the salsolinol-treated rats. CONCLUSIONS: Salsolinol evokes enteric neuronal cell death via initiation of apoptosis and leads to the formation of pathological aggregates of alpha-synuclein. Impairment of myenteric neurons, mainly the inhibitory motor neurons, might be responsible for the abnormal intestinal transit. Thus, salsolinol might be regarded as a suitable compound for inducing experimental enteric neurodegeneration in rats.