Exposure to ambient dusty particulate matter impairs spatial memory and hippocampal LTP by increasing brain inflammation and oxidative stress in rats

OBJECTIVES

Exposure of healthy subjects to ambient airborne dusty particulate matter (PM) causes brain dysfunction. This study aimed to investigate the effect of sub-chronic inhalation of ambient PM in a designed special chamber to create factual dust storm (DS) conditions on spatial cognition, hippocampal long-term potentiation (LTP), inflammatory cytokines, and oxidative stress in the brain tissue.

METHODS

Adult male Wistar rats (250-300 g) were randomly divided into four groups: Sham (clean air, the concentration of dusty PM was <150 μg/m³), DS1 (200-500 μg/m³), DS2 (500-2000 μg/m³) and DS3 (2000-8000 μg/m³). Experimental rats were exposed to clean air or different sizes and concentrations of dust PM storm for four consecutive weeks (exposure was during 1-4, 8-11, 15-16 and 20-23 days, 30 min, twice daily) in a real-ambient dust exposure chamber. Subsequently, cognitive performance, hippocampal LTP, blood-brain barrier (BBB) permeability and brain edema of the animals evaluated. As well as, inflammatory cytokines and oxidative stress indexes in the brain tissue measured using ELISA assays.

RESULTS

Exposing to dust PM impaired spatial memory (p < 0.001), hippocampal LTP (p < 0.001). These disturbances were in line with the severe damage to respiratory system followed by disruption of BBB integrity (p < 0.001), increased brain edema (p < 0.001), inflammatory cytokines (p < 0.001) excretion and oxidative stress (p < 0.001) in brain tissue.

CONCLUSIONS

Our study showed that exposure to ambient dust PM increased brain edema and BBB permeability, induced memory impairment and hippocampal LTP deficiency by increasing the inflammatory responses and oxidative stress in the brain of the rats.

Evaluation of the therapeutic potential effect of Fas receptor gene knockdown in experimental model of non-alcoholic steatohepatitis

Aim: Stimulation of Fas death receptor is introduced as a major cause of non-alcoholic steatohepatitis (NASH) progression through suppression of cell viability. Therefore, the blocking of death pathways is hypothesised to be express new approaches to NASH therapy. For this purpose, current experiment applied synthetic small interference RNA (SiRNA) to trigger Fas death receptor and to show its potential therapeutic role in designed NASH model. Methods: Male mice were placed on a western diet (WD) for 8 weeks and exposed to cigarette smoke during the last 4 weeks of feeding to induce NASH model. In the next step, Fas SiRNA was injected to mice aiming to examine specific Fas gene silencing, after 8 weeks. As a control, mice received scrambled SiRNA. Reversible possibility of disease was examined by 3 weeks of recovery. Results: Analysis of data is accompanied with the significant histopathological changes (steatosis, ballooning and inflammation), increased lipid profile and hepatic enzyme activities (AST, ALT, ALP) plus TBARS as well as decreased antioxidants levels in NASH model. Upon Fas-SiRNA injection, almost all measured parameters of NASH such as overexpression of Fas receptor, caspase3, NF-kB genes and marked increase of hepatic TNF-α were significantly restored and were remained nearly unchanged following recovery liking as scrambled groups. Conclusions: The suppression of Fas receptor signalling subsequent RNAi therapy may represent an applicable strategy to decline hepatocyte damages and so NASH progression in mice.

Ellagic Acid Protects Cardiac Arrhythmias Following Global Cerebral Ischemia/Reperfusion Model

Background:

Cerebral ischemia/reperfusion (I/R) could increase the reactive oxidative stress in the cardiomyocytes. Also, some studies report cardiac arrhythmias following oxidative stressor such as I/R. Hence, this study was aimed to investigate the effects of ellagic acid (EA) against arrhythmias in a cerebral I/R model.

Materials and Methods:

Thirty-two male rats were randomly allocated into four groups: Sham (normal saline, 10 days), EA (100 mg/kg EA, 10 days), I/R (20 min ischemia followed by 30 min reperfusion, 10 days), and EA + I/R (100 mg/kg EA before I/R). In all animals, electrocardiogram (ECG) was recorded pre-ischemia and postischemia on the first and 11th days, respectively.

Results:

The I/R group showed an abnormally prolonged QTc interval after ischemia compared to the preischemia and control groups. EA administration in the EA+I/R group significantly reduced this prolonged QTc interval (P< 0.01). In the I/R group, ischemic/reperfusion resulted in a prolonged QRS complex and an elevated ST, which EA significantly prevented (P<0.01). In addition, EA significantly prevented the dramatically shortened RR interval induced by reperfusion (P<0.01). The incidence of ventricular fibrillation significantly increased in the I/R group; then it dramatically decreased following the administration of EA (P<0.0001).

Conclusion:

EA pretreatment repaired the adverse effects of I/R on the ECG parameters, which can be attributed to its negative chronotropic effects. EA pretreatment can prevent the cerebral I/R-induced heart arrhythmias.

Antidiarrheal effect of sodium hydrosulfide in diabetic rats: In vitro and in vivo studies

BACKGROUND

The inhibitory effects of H₂ S on spontaneous contractions of smooth muscles of small, and large intestines well-established but its role in the pathophysiology of diarrhea has not been identified. Therefore, this study evaluated the role of exogenous H₂ S (NaHS) on diabetic-induced diarrhea and determined mRNA expression of cystathionine β-lyase (CSE) and cystathionine γ-synthase (CBS) in diabetic rats.

METHODS

In order to evaluate antidiarrheal effect of H₂ S, normal and diabetic rats received NaHS and L-Cysteine and the total number of fecal pellets (FP) determined. The effect of NaHS on intestinal transit ratio (ITR) was also evaluated in diabetic rats. The level of mRNA expressions of CBS and CSE determined in smooth muscles of jejunum, ileum, and colon in normal, and diabetic rats. The effect of NaHS on frequency and tension of spontaneous contractions of smooth muscle strips of colon, ileum, and jejunum were investigated.

KEY RESULTS

NaHS decreased ITR, total number of FP, frequency and tension of spontaneous contractions of colon, ileum, and jejunum muscle strips in diabetic rats. The level of mRNA expression of CSE and CBS in diabetic rats were lower than in normal rats. NaHS, and L-Cysteine decreased the number of FP in normal rats.

CONCLUSIONS & INFERENCES

These findings showed NaHS effectively controlled diarrhea in diabetic rats through decreasing the frequency, and tension of spontaneous contraction of smooth muscles of large, and small intestines. The increased frequency and tension of spontaneous contractions of smooth muscles in diabetic rats may be due to down-regulation of H₂ S biosynthesis enzymes.

Delayed gastric emptying in diabetic rats caused by decreased expression of cystathionine gamma lyase and H2 S synthesis: in vitro and in vivo studies

BACKGROUND

This study aimed to evaluate the role of H₂ S on gastric emptying rate (GER) and also to determine the effect of gastric distention on mRNA and protein expression of cystathionine β-lyase (CBS) and cystathionine γ-synthase (CSE) in diabetic-gastroparetic and normal rats.

METHODS

Adult normal rats intraperitoneally received either propargylglycine (PAG), L-cysteine or NaHS 30 min prior to GER marker (acetaminophen) to investigate H₂ S involvement in GER and the same protocols were performed in diabetes-induced gastroparesis rats. The role of calcitonin gene related peptide (CGRP) neurons in the prokinetic effect of endogenous H₂ S on GER was determined. The level of CBS and CSE expressions in response to gastric distention were also determined. The effect of H₂ S on frequency and tension of spontaneous contractions of gastric smooth muscle strips was investigated.

KEY RESULTS

Our results showed that: (i) H₂ S and L-cysteine increased GER in gastroparetic and normal rats. (ii) The increased levels of CSE expression in response to gastric distention in diabetic rats were lower than in normal rats. (iii) PAG inhibited the excitatory effect of capsaicin on GER and on tension of spontaneous contractions of strips. (iv) Hydrogen sulphide increased the frequency and tension of spontaneous contractions of gastric strip muscles in normal and diabetic rats.

CONCLUSIONS & INFERENCES

The results showed that delayed GER in diabetic rats can be due to down-regulation of H₂ S biosynthesis enzyme, CSE and suggested that a potential prokinetic role for H₂ S to treat the delayed gastric emptying in diabetic patients.

Mucosal acidification increases hydrogen sulfide release through up-regulating gene and protein expressions of cystathionine gamma-lyase in the rat gastric mucosa

OBJECTIVES

This study was performed to investigate the effects of mucosal acidification on mRNA expression and protein synthesis of cystathionine gamma lyase (CSE), cystathionine beta synthase (CBS), and mucosal release of H2S in gastric mucosa in rats.

MATERIALS AND METHODS

Thirty-two rats were randomly assigned into 4 groups (8 in each), including: the control group, HCl (10 mM) treated group, HCl (100 mM) treated group, and one group to study the effect of Nω-Nitro-L-arginine methyl ester hydrochloride (L-NAME). Anesthetized rats underwent tracheostomy and midline laparotomy. Ninety min after the instillation of neutral or acidic solutions, animals were sacrificed and the gastric mucosa was collected to measure the H2S concentration by ELISA method and to quantify mRNA expression of CSE and CBS by quantitative real-time PCR (qRT-PCR). Protein synthesis was also detected by Western blot method.

RESULTS

Mucosal acidification with 10 and 100 HCl, significantly increased mucosal levels of H2S (P<0.01 and P<0.001) and mRNA (P<0.01 and P<0.001) and protein expressions of CSE (P<0.01 and P<0.001). L-NAME treatment reversed H2S release to control level.

CONCLUSION

Our findings indicated that mucosal acidification with HCl increased mucosal release of H2S through upregulation of CSE gene and its protein expression. This effect is mainly mediated through the involvement of nitric oxide.

Gastric acid induces mucosal H2S release in rats by upregulating mRNA and protein expression of cystathionine gamma lyase

It is well known that hydrogen sulfide (H2S) protects the gastric mucosa against gastric acid and other noxious stimulants by several mechanisms but until now the effect of gastric acid on H2S production has not been evaluated. This study was performed to determine the effect of basal and stimulated gastric acid secretion on mRNA and protein expression of cystathionine gamma lyase (CSE) and cystathionine beta synthase (CBS), and on mucosal release of H2S in rats. Seventy-two male rats were randomly assigned into 9 groups (8 in each)-control, distention, and pentagastrin-induced gastric acid secretion groups. The effects of 15% alcohol solution, propargylglycine (PAG), L-NAME, and pantoprazole were also investigated. Under anesthesia, animals underwent tracheostomy and midline laparotomy. A catheter was inserted into the stomach through the duodenum for gastric washout. At the end of the experiments, the animals were killed and the gastric mucosa was collected to measure H2S concentration and to quantify mRNA expression of CSE and CBS by quantitative real-time PCR, and expression of their proteins by western blot. Basal and stimulated gastric acid secretion increased mucosal levels of H2S, and mRNA and protein expression of CSE. Pantoprazole and L-NAME reversed H2S release and restored protein expression of CSE to the control level. Pantoprazole, but not propargylglycine, pretreatment inhibited the elevated level of protein expression of eNOS in response to distention-induced gastric acid secretion. Our findings indicated that NO mediated the stimulatory effect of gastric acid on H2S release and protein expression of CSE.

Gallic acid improved behavior, brain electrophysiology, and inflammation in a rat model of traumatic brain injury

Traumatic brain injury (TBI) is one of the main causes of intellectual and cognitive disabilities. In the clinic it is essential to limit the development of cognitive impairment after TBI. In this study, the effects of gallic acid (GA; 100 mg/kg, per oral, from 7 days before to 2 days after TBI induction) on neurological score, passive avoidance memory, long-term potentiation (LTP) deficits, and levels of proinflammatory cytokines including interleukin-1 beta (IL-1β), interleukin 6 (IL-6), and tumor necrosis factor-α (TNF-α) in the brain have been evaluated. Brain injury was induced following Marmarou’s method. Data were analyzed by one-way and repeated measures ANOVA followed by Tukey’s post-hoc test. The results indicated that memory was significantly impaired (p < 0.001) in the group treated with TBI + vehicle, together with deterioration of the hippocampal LTP and increased brain tissue levels of IL-1β, IL-6, and TNF-α. GA treatment significantly improved memory and LTP in the TBI rats. The brain tissue levels of IL-1β, IL-6, and TNF-α were significantly reduced (p < 0.001) in the group treated with GA. The results suggest that GA has neuroprotective properties against TBI-induced behavioral, electrophysiological, and inflammatory disorders, probably via the decrease of cerebral proinflammatory cytokines.

Bronchodilatory effect of hydrogen sulfide in rat

OBJECTIVE(S)

The aims of present study were to elucidate the effect of NaHS as a H2S donor on precontracted rat trachea smooth muscle, role of epithelium and nitric oxide in this action.

MATERIALS AND METHODS

Tracheal rings from male adult Wistar rats were isolated and mounted in an organ bath containing Krebs-Henseleit solution under 1.5 g resting tension and contractions were recorded isometrically. After equilibrium period (60 min), cumulative concentrations of NaHS (0.2-1.2 mM) were applied on the tracheal basal tone or on the plateau of contractions induced by KCl (60 mM) or carbachol (CCh, 0.55 μM) in the absence and presence of certain antagonists and inhibitors.

RESULTS

The tracheal basal tone was unaffected by NaHS but tracheal contractions induced by KCl and CCh were attenuated by NaHS in a concentration-dependent manner (P< 0.001). Removing the tracheal epithelial did not attenuate the NaHS spasmolytic effect in the tissue precontracted by KCl and CCh. The bronchodilatory effect was unaffected by tissue incubation (30 min, 1 μM) with, glibenclamide, propranolol, indomethacin, methylene blue (10 μM), and L-NAME (300 μM).

CONCLUSION

It seems that bronchodilatory effect of H2S was not mediated by KATP channels, β-adrenoceptors, epithelium and production of nitric oxide, cGMP and prostaglandins. Since CCh and KCl activate Ca(2+) influx and CCh promotes Ca(2+) from intracellular pool as well, therefore, we may conclude that the relaxant effect of NaHS was mediated by the Ca(2+) influx blockade and cholinergic receptors inactivation. This preliminary study shows the possible therapeutical property of H2S in obstructive pulmonary diseases.

Plasticity in the gastric inhibitory innervation after immunization against VIP and vagotomy in the ferret

Changes in gastric corpus tone have been characterized during two procedures that compromise the major inhibitory innervation of the stomach: immunoneutralization of endogenous vasoactive intestinal polypeptide (VIP) and chronic vagotomy. After both procedures, there was a small but significant increase in intracorpus pressure generated during ramp increases in volume compared with sham immunized controls but not when the procedures were combined in vagotomized immunized animals. Adaptation in the mechanisms controlling corpus tone was most apparent after atropine (100 micrograms/kg) and acute vagal section when tone was low in sham immunized vagotomized and vagotomized immunized animals (4.4 +/- 0.3 and 3.7 +/- 0.8 cmH2O, respectively) and high in immunized and sham immunized animals (6.5 +/- 0.4 and 6.2 +/- 0.5 cmH2O) despite a similar sensitivity to atropine. Corpus responses to low-frequency vagal stimulation were maintained in immunized animals despite the absence of a response to exogenous VIP. We conclude that gastric reservoir function adapts to the loss of the vagal inhibitory innervation by an upregulation of intrinsic reflex pathways controlling myenteric inhibitory neurons, which are non-VIPergic.

Role of nitric oxide and vasoactive intestinal polypeptide in vagally mediated relaxation of the gastric corpus in the anaesthetized ferret

The roles of VIP and NO in vagally mediated relaxations of the gastric corpus were investigated in the anaesthetized ferret. Intracorpus pressure was recorded manometrically during electrical stimulation of the cervical vagus nerve in three groups of animals: one control group (n = 6), one group treated with an inhibitor of NO synthesis (NG-nitro-L-arginine methyl ester (L-NAME), 1.6 mg/kg); and a third group which had been immunized, prior to the experiment, with a VIP-thyroglobulin conjugate (25 nmol equivalent) in Freund's complete adjuvant. In control animals, following treatment with atropine (100 micrograms/kg), vagal stimulation resulted in a frequency dependent fall in intracorpus pressure with the maximum response at 5 Hz of 2.2 +/- 0.3 cm H2O. Two components of the response could be observed: an initial rapid fall over the first 10 s of stimulation followed by a slower decline over the remainder of the stimulation period. In animals treated with L-NAME (n = 6) the initial rapid response was significantly reduced at all frequencies of stimulation (P < 0.05 - P < 0.005, Mann-Whitney U-test) leaving only the slower second component. In immunized animals (n = 6) the initial rapid response to vagal stimulation was not different from control but the slower second component was significantly reduced at 1 Hz (P < 0.005). We conclude that the response to vagal stimulation appears to consist of two components which can be differentiated using L-NAME and autoimmunization to VIP.

Effect of immunisation against vasoactive intestinal polypeptide on gastric corpus tone and motility in the ferret

The role of vasoactive intestinal polypeptide in the control of gastric corpus tone and motility was investigated using auto-antibodies to neutralise endogenous vasoactive intestinal polypeptide. Six ferrets were immunised with vasoactive intestinal polypeptide thyroglobulin conjugate in Freund's complete adjuvant which resulted in a significant increase in plasma vasoactive intestinal polypeptide binding activity compared with unimmunised control animals. In acute experiments the level of spontaneous motility in the period immediately after completion of the surgical preparation was 15 times higher in immunised v control animals (p < 0.02). Surprisingly, however, there was no deficit in the ability of the corpus to accommodate fluid. Peak pressure at the end of a 20 ml ramp distension was not different in immunised animals (5.7 (0.6) cm H2O) compared with controls (4.8 (0.3) cm H2O). It is concluded that the non-adrenergic non-cholinergic inhibitory mechanisms regulating corpus tone and motility are different and that vasoactive intestinal polypeptide acts primarily to regulate phasic contractile activity. Alternatively, because of plasticity in the mechanisms controlling corpus tone, the effect of vasoactive intestinal polypeptide may have been superceded during the timecourse of the immunisation procedure.