Alessandra Ottani

Hydrogen sulfide slows down progression of experimental Alzheimer’s disease by targeting multiple pathophysiological mechanisms

It has been previously reported that brain hydrogen sulfide (H2S) synthesis is severely decreased in Alzheimers disease (AD) patients, and plasma H2S levels are negatively correlated with the severity of AD. Here we extensively investigated whether treatment with a H2S donor and spa-waters rich in H2S induces neuroprotection and slows down progression of AD. Studies with sodium hydrosulfide (a H2S donor) and Tabianos spa-water were carried out in three experimental models of AD. Short-term and long-term treatments with sodium hydrosulfide and/or Tabianos spa-water significantly protected against impairment in learning and memory in rat models of AD induced by brain injection of β-amyloid1-40 (Aβ) or streptozotocin, and in an AD mouse model harboring human transgenes APPSwe, PS1M146V and tauP301L (3xTg-AD mice). The improvement in behavioral performance was associated with hippocampus was size of Aβ plaques and preservation of the morphological picture, as found in AD rats. Further, lowered concentration/phosphorylation levels of proteins thought to be the central events in AD pathophysiology, namely amyloid precursor protein, presenilin-1, Aβ1-42 and tau phosphorylated at Thr181, Ser396 and Ser202, were detected in 3xTg-AD mice treated with spa-water. The excitotoxicity-triggered oxidative and nitrosative stress was counteracted in 3xTg-AD mice, as indicated by the decreased levels of malondialdehyde and nitrites in the cerebral cortex. Hippocampus reduced activity of c-jun N-terminal kinases, extracellular signal-regulated kinases and p38, which have an established role not only in phosphorylation of tau protein but also in inflammation and apoptosis, was also found. Consistently, decrease in tumor necrosis factor-α level, up-regulation of Bcl-2, and down-regulation of BAX and the downstream executioner caspase-3, also occurred in the hippocampus of 3xTg-AD mice after treatment with Tabianos spa-water, thus suggesting that it is also able to modulate inflammation and apoptosis. Our findings indicate that appropriate treatments with H2S donors and Tabianos spa-waters, and may be other spa-waters rich in H2S content, might represent an innovative approach to slow down AD progression in humans by targeting multiple pathophysiological mechanisms.

Dual acting anti-inflammatory drugs

Drugs able to inhibit both cyclooxygenases (COX-1 and COX-2) and 5-lipoxygenase (5-LOX) (dual acting anti-inflammatory drugs) have been designed in order to obtain compounds that retain the activity of classical nonsteroidal anti-inflammatory drugs (NSAIDs) while avoiding their main drawbacks. The classical NSAIDs display their anti-inflammatory action mainly through inhibition of COX and one of their main drawbacks is the curtailed production of gastroprotective prostaglandins (PGs) being associated with the concurrent increased production of the gastro-damaging and bronchoconstrictive leukotrienes (LTs). Leukotrienes and cysteinyl-leukotrienes are moreover pro-inflammatory and increase microvascular permeability. One of the leukotrienes (LTB(4)) is the most potent chemotactic agent and it induces chemotaxis of eosinophils, neutrophils and monocytes in the inflamed tissue, increases superoxide generation and proinflammatory cytokines production. It is further advantageous for a drug to have both COX and 5-LOX inhibiting activities because prostaglandins enhance leukotriene-mediated inflammation. Various structural families of dual inhibitors have been designed and several compounds are currently undergoing clinical development. In the post-COX-2 selective inhibitors era, these dual acting inhibitors may turn out to be promising new drugs to treat inflammatory diseases and possibly other diseases. Indeed, both COX-2 and 5-LOX are also involved in the development and progression of several types of cancer; in these conditions, selective inhibition of COX-2 alone may lead to a shunt of arachidonic acid metabolism towards the leukotriene pathway, and therefore the blockade of both COX-2 and 5-LOX may produce a better anticancer response. In addition, the dual inhibition of both COX and 5-LOX is neuroprotective by suppressing toxic actions of reactive microglia and macrophages, that are increased in aging brain and in age-related degenerative conditions, particularly Alzheimers and Parkinsons diseases. Finally, the blockade of 5-LOX does not impair the synthesis of lipoxins (LXs), which are mainly produced by further lipoxygenation of 15-HPETE, and which have potent anti-inflammatory properties and can be considered as stop-signal mediators. Leukocyte 15-LOX and platelet 12-LOX by intercellular mechanism via leukocyte/platelet cell-cell interaction convert 15-HPETE into lipoxins.

Similarities and differences between chronic migraine and episodic migraine

Objective.—To quantify and characterize the similarities and the differences between chronic migraine (CM) patients with medication overuse and episodic migraine (EM) patients with only occasional analgesic use.

Vagus nerve mediates the protective effects of melanocortins against cerebral and systemic damage after ischemic stroke.

A vagus nerve-mediated, efferent cholinergic protective pathway activated by melanocortins is operative in circulatory shock and myocardial ischemia. Moreover, melanocortins have neuroprotective effects against brain damage after ischemic stroke. Here we investigated cerebral and systemic pathophysiologic reactions to focal cerebral ischemia in rats induced by intrastriatal microinjection of endothelin-1, and the possible protective role of the melanocortin-activated vagal cholinergic pathway. In the striatum and liver of saline-treated control rats, the activation of extracellular signal-regulated kinases, c-jun N-terminal kinases, and caspase-3, the increase in tumor necrosis factor-α (TNF-α) concentration and DNA fragmentation, as well as the increase in TNF-α plasma levels, occurred 10 and 20 h after the ischemic insult suggesting an activation of inflammatory and apoptotic responses. Treatment with [Nle4, D-Phe7]α-melanocyte-stimulating hormone (NDP-α-MSH; 3 or 9 h after stroke) suppressed the inflammatory and apoptotic cascades at central and peripheral level. Bilateral vagotomy and pharmacologic blockade of peripheral nicotinic acetylcholine receptors blunted the protective effect of NDP-α-MSH. The present results show that focal brain ischemia in rats causes significant effects not only in the brain, but also in the liver. Moreover, our data support the hypothesis that a protective, melanocortin-activated, vagal cholinergic pathway is likely operative in conditions of ischemic stroke.

Effect of acute and chronic treatment with triiodothyronine on serotonin levels and serotonergic receptor subtypes in the rat brain

Hyperthyroidism is often associated with behavioral disorders, and thyroid hormones modify receptor sensitivity as well as the synthesis and/or turnover rate of many neurotransmitters. We evaluated the influence in adult rats of triiodothyronine (T3), administered s.c. (100 micrograms/kg) acutely (once only) or chronically (once a day for 3 or 7 consecutive days), on brain serotonin concentration and on the density and affinity of two brain serotonin (5-HT) receptor subtypes mainly involved in behavioral effects. After both acute and chronic T3 treatment, serotonin levels increased in the cerebral cortex but not in the hippocampus. The density and affinity of 5-HT1A receptors (using [3H]-8-OH-DPAT as ligand) were not affected, while there was a significant decrease in the number of 5-HT2 receptors in the cerebral cortex (using [3H]ketanserin as ligand). This observation might indicate that thyroid hormones enhance 5-HT concentration in certain brain areas, thus causing a down-regulation of 5-HT2 receptors. The serotonergic system could be involved in the complex brain-neurotransmitter imbalance underlying hyperthyroidism-linked behavioral changes.

Streptozotocin-induced diabetes provokes changes in serotonin concentration and on 5-HT1A and 5-HT2 receptors in the rat brain

Since reduced levels of brain serotonin are known to cause behavioural abnormalities, to which diabetics are also prone, we investigated the effect, in rats, of chronic diabetes on brain serotonin concentration and on the numbers of 5-HT(1A) and 5-HT2 receptors in cerebral cortex and brainstem. Our data show that streptozotocin induces a longlasting hyperglicemia that is associated with a decrease in cerebral concentration of serotonin and with an accompanying increase in the maximum number of 5-HT(1A) and 5-HT2 receptors in the brain areas studied. Our results may suggest that changes in serotonergic transmission in the CNS play a role in diabetes-related behavioural abnormalities.

Effect of γ-hydroxybutyrate in two rat models of focal cerebral damage

Abstract γ-Hydroxybutyrate (GHB) and its lactone, γ-butyrolactone (GBL) have been previously shown to produce a protective effect in animal models of cerebral ischaemia/hypoxia, as well as in human conditions of head injury-induced coma. The aim of the present research was to study the effect of GHB in experimental conditions of focal cerebral damage, either induced by ischaemia or excitotoxicity. Under general anaesthesia, rats were injected into the right striatum with either endothelin-1 (ET-1, 0.43 nmol) or kainic acid (7.5 nmol) in a volume of 1 μl. Sham-lesioned rats received 1 μl of the solvent. Both ET-1- and kainic acid-lesioned rats were randomly assigned to one of the following intraperitoneal (i.p.) treatments: (i) and (ii) GHB, 100 or 300 mg kg −1 2 h after the lesion, followed by 50 or 100 mg kg −1 , respectively, every 12 h; (iii) saline, 2 ml kg −1 , same schedule. Sham animals were treated with saline, 2 ml kg −1 , same schedule. Treatments lasted for 10 days. The higher dose of GHB produced a significant protection against the ET-1-induced impairments in sensory-motor orientation and coordinated limb use (evaluated 24 and 42 days after the lesion) and in place learning and memory (Morris test, performed 19 and 39 days after the lesion). The same dose regimen reduced the circling behaviour induced by apomorphine in kainate-lesioned rats (10 days after the lesion), and limited or prevented at all the histological damage produced either by ET-1 or by kainic acid (evaluated 43 or 10 days after the lesion, respectively). These results show that GHB limits both histological and functional consequences of a focal ischaemic or excitotoxic insult of the brain, in rats, even if the treatment is started 2 h after the lesion.

Regulation of hypothalamic endocannabinoid levels by neuropeptides and hormones involved in food intake and metabolism: insulin and melanocortins.

Endocannabinoids are paracrine/autocrine lipid mediators with several biological functions. One of these, i.e. the capability to stimulate food intake via cannabinoid CB(1) receptors, has been particularly studied, thus leading to the development of the first CB(1) receptor blocker, rimonabant, as a therapeutic tool against obesity and related metabolic disorders. Hypothalamic endocannabinoids stimulate appetite by regulating the expression and release of anorexic and orexigenic neuropeptides via CB(1) receptors. In turn, the tone of the latter receptors is regulated by hormones, including leptin, glucocorticoids and possibly ghrelin and neuropeptide Y, by modulating the biosynthesis of the endocannabinoids in various areas of the hypothalamus. CB(1) receptor stimulation is also known to increase blood glucose during an oral glucose tolerance test in rats. Here we investigated in the rat if insulin, which is known to exert fundamental actions at the level of the mediobasal hypothalamus (MBH), and the melanocortin system, namely alpha-melanocyte stimulating hormone (alpha-MSH) and melanocortin receptor-4 (MCR-4), also regulate hypothalamic endocannabinoid levels, measured by isotope-dilution liquid chromatography coupled to mass spectrometry. No effect on anandamide and 2-arachidonoylglycerol levels was observed after 2h infusion of insulin in the MBH, i.e. under conditions in which the hormone reduces blood glucose, nor with intra-cerebroventricular injection of alpha-MSH, under conditions in which the neuropeptide reduces food intake. Conversely, blockade of MCR-4 receptors with HS014 produced a late (6h after systemic administration) stimulatory effect on endocannabinoid levels as opposed to a rapid and prolonged stimulation of food-intake (observable 2 and 6h after administration). These data suggest that inhibition of endocannabinoid levels does not mediate the effect of insulin on hepatic glucose production nor the food intake-inhibitory effect of alpha-MSH, although stimulation of endocannabinoid levels might underlie part of the late stimulatory effects of MCR-4 blockade on food intake.

Influence of sildenafil on central dopamine-mediated behaviour in male rats

Two experiments were performed to evaluate the effects of sildenafil on spontaneous or dopamine agonist-induced behaviour in male rats. Data obtained in experiment 1 show that oral administration of the drug, at 1 mg/kg, significantly increased the occurrence of penile erections, anogenital self-grooming and homosexual mounting in grouped sexually-experienced, but not inexperienced, animals. In experiment 2, pre-treatment with sildenafil (0.5, 1 or 10 mg/kg) dose-dependently modified several behavioural signs, centrally evoked by the D2/D3 dopamine agonists, 7-OH-DPAT or B-HT 920 (both at 0.1 mg/kg), in experimentally naive male rats. While sildenafil at 1 mg/kg significantly increased the number of penile erection and stretching-yawning episodes induced by 7-OH-DPAT or B-HT 920, at 10 mg/kg it elicited low stereotyped behaviour, antagonizing stretching-yawning and sedation in 7-OH-DPAT treated rats. Discussion centres on the modulatory activity of sildenafil on central dopaminergic pathways and, possibly, on nitric oxide production.

Influence of the cannabinoid agonist HU 210 on cocaine- and CQP 201-403-induced behavioural effects in rat.

Acute injection of the cannabinoid agonist HU 210 (6.25-100 microg/kg, i.p.) dose-dependently inhibited rat locomotor activity and rearing, while subchronic treatment with the drug (once daily for 7 days) at the same doses only diminished locomotion. Acute but not subchronic administration of HU 210 (12.5-50 microg/kg, i.p.) potently counteracted acute and subchronic cocaine (15 mg/kg, i.p.)-induced hyperlocomotion and enhanced rearing. The acute cannabinoid (6.25-100 microg/kg, i.p.) also inhibited locomotor activity, stereotyped behaviour and shaking elicited by the D1/D2 agonist CQP 201-403 (500 microg/kg, i.p.). On the contrary, subchronic treatments with HU 210 enhanced CQP 201-403-induced locomotor activity and potently stimulated escape attempts. Discussion centers on the influence of cannabinoids on experimental models of psychosis.