Effects of ghrelin on sulfite induced changes in lipid peroxidation, spatial memory, and locomotor activity in rats.

BACKGROUND: Humans are constantly exposed to sulfites and their derivatives, both endogenously and exogenously. Recent studies have shown that sulfite and its derivatives can cause oxidative stress. . Ghrelin has been reported to possess antioxidant properties and stimulates neurogenesis in hippocampal progenitor cells. This study aimed to investigate the effects of ghrelin on sulfite-induced changes in hippocampal oxidative status, spatial learning and locomotor activity in rats. METHODS: Forty male albino Wistar rats were randomized into four groups as follows; Group 1: Control (C); Group 2: Sodium metabisulfite (Na2S2O5) treated (S); Group 3: Ghrelin treated (G); Group 4: Na2S2O5 + Ghrelin treated (SG). Sodium metabisulfite (100 mg/kg/day) was given by gastric gavage, and ghrelin (20 µg/kg/day) was administered intraperitoneally for 5 weeks. Thiobarbituric acid reactive substances (TBARS) were measured through fluorometric method. The spatial memory and locomotor activity of the rats were evaluated by Y-maze test. RESULTS: Y-maze results revealed an enhancement of short-term spatial learning and memory in S and SG groups compared to C group. TBARS levels were increased significantly in S group with respect to C group. The increase in TBARS levels induced by sulfite was completely prevented by ghrelin in SG group. CONCLUSION: We suggest that systemic ghrelin administration might ameliorate ingested sodium metabisulfite-induced hippocampal oxidative damage without providing any changes in spatial learning, memory and locomotion. Further investigation concerning the mechanism of ghrelin action in hippocampus might provide valuable information for developing new therapeutic approaches to attenuate oxidative stress in hippocampal tissue.

The effect of increase in blood glucose level on hearing loss

Abstract Objective: Previous studies have shown that hearing function is also vulnerable to the effects of diabetes mellitus which can be shown by brainstem auditory evoked potential and distortion product otoacoustic emission recordings. This study aimed to investigate the changes of brainstem auditory evoked potential and distortion product otoacoustic emission in hyperglycemia and whether there is a relationship between reactive oxygen substances production and hearing deterioration in the rat model. Methods: 25 streptozotocin induced diabetic rats were divided into three groups: control, high blood glucose, and diabetes mellitus. Brainstem auditory evoked potential and distortion product otoacoustic emission were recorded, and thiobarbituric acid reactive substances levels were measured in the brainstem tissue. Results: At 8 kHz, the latencies of I, II, III, IV, and V brainstem auditory evoked potential waves in high blood glucose and diabetes mellitus groups were elongated, at 16 kHz, only these wave latencies of the diabetes mellitus group were prolonged compared with the control group. A significant decrease was also found in distortion product otoacoustic emission amplitudes at 4, 6, 8, and 10 kHz in the high blood glucose and diabetes mellitus groups compared to the control group. There was a significant increase in thiobarbituric acid reactive substances values due to the increase in blood glucose levels in the high blood glucose and diabetes mellitus groups compared to the control group. Conclusion: These results suggested that high blood glucose levels may cause hearing impairment not only in the diabetic state but also in the period of hyperglycemia before the onset of manifest diabetes mellitus and reactive oxygen substances may play an important role in the pathophysiology of diabetes mellitus. We suggest that regulating high glucose levels even before the onset of manifest diabetes mellitus may prevent hazardous effects on hearing function. Level of evidence: Level 3.

The effect of increase in blood glucose level on hearing loss.

OBJECTIVE: Previous studies have shown that hearing function is also vulnerable to the effects of diabetes mellitus which can be shown by brainstem auditory evoked potential and distortion product otoacoustic emission recordings. This study aimed to investigate the changes of brainstem auditory evoked potential and distortion product otoacoustic emission in hyperglycemia and whether there is a relationship between reactive oxygen substances production and hearing deterioration in the rat model. METHODS: 25 streptozotocin induced diabetic rats were divided into three groups: control, high blood glucose, and diabetes mellitus. Brainstem auditory evoked potential and distortion product otoacoustic emission were recorded, and thiobarbituric acid reactive substances levels were measured in the brainstem tissue. RESULTS: At 8 kHz, the latencies of I, II, III, IV, and V brainstem auditory evoked potential waves in high blood glucose and diabetes mellitus groups were elongated, at 16 kHz, only these wave latencies of the diabetes mellitus group were prolonged compared with the control group. A significant decrease was also found in distortion product otoacoustic emission amplitudes at 4, 6, 8, and 10 kHz in the high blood glucose and diabetes mellitus groups compared to the control group. There was a significant increase in thiobarbituric acid reactive substances values due to the increase in blood glucose levels in the high blood glucose and diabetes mellitus groups compared to the control group. CONCLUSION: These results suggested that high blood glucose levels may cause hearing impairment not only in the diabetic state but also in the period of hyperglycemia before the onset of manifest diabetes mellitus and reactive oxygen substances may play an important role in the pathophysiology of diabetes mellitus. We suggest that regulating high glucose levels even before the onset of manifest diabetes mellitus may prevent hazardous effects on hearing function. LEVEL OF EVIDENCE: Level 3.

The effects of acute and chronic exposure to 900 MHz radiofrequency radiation on auditory brainstem response in adult rats.

The aim of this study was to determine the effects of short and long-term RFR exposure on ABR by evaluating lipid peroxidation and antioxidant status in adult rats. Sixty male albino Wistar rats were randomly divided into four groups. S1:1 week sham, S10:10 weeks sham, E1:1 week RFR, E10:10 weeks RFR. Experimental group rats were exposed to RFR 2 h/day, 5 days/week during the test period. Sham rats were kept in the same conditions without RFR. After the experiment, ABRs were recorded from the mastoids of rats using tone burst acoustic stimuli. Biochemical investigations in rat brain and ultrastructural analysis in temporal cortex were performed. ABR wave I latency prolonged in E1-group and shortened in E10-group compared to their shams. TBARS level increased in E1-group, decreased in E10-group, on the contrary, SOD and CAT activities and GSH level decreased in E1-group, increased in E10-group compared to their sham groups. Edema was present in the neuron and astrocyte cytoplasms and astrocyte end-feet in both E1 and E10 groups. Our results suggest that 900 MHz RFR may have negative effects on the auditory system in acute exposure and no adverse effects in chronic exposure without weekends.

The effects of sulfite on cPLA2, caspase-3, oxidative stress and locomotor activity in rats.

Sulfite is a commonly used preservative in food products, alcoholic beverages and pharmaceutical products. We investigated the effect of sulfite, on locomotor activity as well as the relationship of these effects with oxidant and antioxidant capacities, cPLA2 enzyme activity. Thirty male Wistar albino rats were randomly divided into two groups as control(C) and sulfite(S). Animals in the S group were given freshly prepared sulfite for 35 days via gastric gavage (100 mg/kg/day) while the C group received equal volumes of distilled water via gavage for the same period. Open-field tests were performed to all groups and animals were sacrificed. Total antioxidant capacity(TAC), TBARS levels, cPLA2 activity as well as amount of caspase-3 positive cells were analyzed on the hippocampi. In the open field test, distance and velocity values of the S group increased with respect to controls. TBARS and cPLA2 activity were also increased in the S group, while levels of TAC decreased compared to controls. Immunohistochemical analysis showed that sulfite ingestion caused an increase in the amount of hippocampal caspase-3 positive cells. In conclusion, sulfite seemed to increase locomotor activity. cPLA2 might play a role in ingested sulfite-induced oxidative stress and apoptotic cell death in the hippocampus.

Effect of sodium tungstate on visual evoked potentials in diabetic rats.

AIM: To evaluate the effect of sodium tungstate on visual evoked potentials (VEPs) in diabetic rats. METHODS: Wistar rats were randomly divided into three groups as normal control, diabetic control and diabetic rats treated with sodium tungstate. Diabetes was induced by single intraperitoneal injection of streptozotocin (50 mg/kg). Sodium tungstate [40 mg/(kg·d)] was administered for 12wk and then VEPs were recorded. Additionally, thiobarbituric acid reactive substance (TBARS) levels were measured in brain tissues. RESULTS: The latencies of P1, N1, P2, N2 and P3 waves were significantly prolonged in diabetic rats compared with control group. Diabetes mellitus caused an increase in the lipid peroxidation process that was accompanied by changes in VEPs. However, prolonged latencies of VEPs for all components returned to control levels in sodium tungstate-treated group. The treatment of sodium tungstate significantly decreased brain TBARS levels and depleted the prolonged latencies of VEP components compared with diabetic control group. CONCLUSION: Sodium tungstate shows protective effects on visual pathway in diabetic rats, and it can be worthy of further study for potential use.

Induction of omega 6 inflammatory pathway by sodium metabisulfite in rat liver and its attenuation by ghrelin.

BACKGROUND: Sodium metabisulfite is commonly used as preservative in foods but can oxidize to sulfite radicals initiating molecular oxidation. Ghrelin is a peptide hormone primarily produced in the stomach and has anti-inflammatory effects in many organs. This study aimed to assess endogenous omega-3 (n-3) and omega-6 (n-6) polyunsaturated fatty acids (PUFAs) in rat peripheral organs following sodium metabisulfite treatment and determine the possible effect of ghrelin on changes in n-6 inflammatory pathway. METHODS: Male Wistar rats included in the study were allowed free access to standard rat chow. Sodium metabisulfite was given by gastric gavage and ghrelin was administered intraperitoneally for 5 weeks. Levels of arachidonic acid (AA, C20:4n-6), dihomo-gamma-linolenic acid (DGLA, C20:3n-6), eicosapentaenoic acid (EPA, C20:5n-3) and docosahexaenoic acid (DHA, C22:6n-3) in liver, heart and kidney tissues were determined by an optimized multiple reaction monitoring (MRM) method using ultra fast-liquid chromatography (UFLC) coupled with tandem mass spectrometry (MS/MS). Cyclooxygenase (COX) and prostaglandin E2 (PGE2) were measured in tissue samples to evaluate changes in n-6 inflammatory pathway. RESULTS: Omega-6 PUFA levels, AA/DHA and AA/EPA ratio were significantly increased in liver tissue following sodium metabisulfite treatment compared to controls. No significant change was observed in heart and kidney PUFA levels. Tissue activity of COX and PGE2 levels were also significantly increased in liver tissue of sodium metabisulfite treated rats compared to controls. Ghrelin treatment decreased n-6 PUFA levels and reduced COX and PGE2 levels in liver tissue of sodium metabisulfite treated rats. CONCLUSION: Current results suggest that ghrelin exerts anti-inflammatory action through modulation of n-6 PUFA levels in hepatic tissue.

Induction of xanthine oxidase activity, endoplasmic reticulum stress and caspase activation by sodium metabisulfite in rat liver and their attenuation by Ghrelin.

Sodium metabisulfite is used as a preservative in many food preparations but can oxidize to sulfite radicals initiating molecular oxidation. Ghrelin is a peptide hormone primarily produced in the stomach and has anti-inflammatory and anti-oxidant effects on gastrointestinal and cardiovascular systems. This study was performed to elucidate the effect of ghrelin on sulfite-induced endoplasmic reticulum (ER) stress and caspase activation in rat peripheral organs. Xanthine oxidase (XO), xanthine dehydrogenase (XDH) enzyme activities, ER stress markers [phosphorylated PKR-like ER kinase (pPERK); C/EBP-homologous protein (CHOP)], caspase-3, -8, -9 activities, nuclear factor kappa-B (NF-κB) levels were determined in liver, heart and kidney of rats treated with sodium metabisulfite and/or ghrelin for 5 weeks. Sodium metabisulfite treatment significantly elevated XO activity, induced expression of GRP78, CHOP and increased caspase-3, -8 and -9 activities in liver but had no significant effect in heart and kidney. Ghrelin treatment decreased XO activity to baseline levels and attenuated ER stress and caspase activation in liver tissue of sodium metabisulfite treated rats. In conclusion, metabolism of sodium metabisulfite in liver tissue increased XO activity, induced ER stress and caused caspase activation which was attenuated by ghrelin treatment. Ghrelin's hepatoprotective effect could be through modulation of XO activity.

Inhibition of neutral sphingomyelinase decreases elevated levels of inducible nitric oxide synthase and apoptotic cell death in ocular hypertensive rats.

Endoplasmic reticulum (ER) stress and excessive nitric oxide production via induction of inducible nitric oxide synthase (NOS2) have been implicated in the pathogenesis of neuronal retinal cell death in ocular hypertension. Neutral sphingomyelinase (N-SMase)/ceramide pathway can regulate NOS2 expression, hence this study determined the role of selective neutral sphingomyelinase (N-SMase) inhibition on retinal NOS2 levels, ER stress, apoptosis and visual evoked potentials (VEPs) in a rat model of elevated intraocular pressure (EIOP). NOS2 expression and retinal protein nitration were significantly greater in EIOP and significantly decreased with N-SMase inhibition. A significant increase was observed in retinal ER stress markers pPERK, CHOP and GRP78 in EIOP, which were not significantly altered by N-SMase inhibition. Retinal TUNEL staining showed increased apoptosis in all EIOP groups; however N-SMase inhibition significantly decreased the percent of apoptotic cells in EIOP. Caspase-3, -8 and -9 activities were significantly increased in EIOP and returned to baseline levels following N-SMase inhibition. Latencies of all VEP components were significantly prolonged in EIOP and shortened following N-SMase inhibition. Data confirm the role of nitrative injury in EIOP and highlight the protective effect of N-SMase inhibition in EIOP via down-regulation of NOS2 levels and nitrative stress.

Ghrelin inhibits sodium metabisulfite induced oxidative stress and apoptosis in rat gastric mucosa.

This study aimed to investigate the effect of ghrelin administration on sulfite induced oxidative and apoptotic changes in rat gastric mucosa. Forty male albino Wistar rats were randomized into control (C), sodium metabisulfite (Na2S2O5) treated (S), ghrelin treated (G) and, Na2S2O5+ghrelin treated (SG) groups. Sodium metabisulfite (100 mg/kg/day) was given by gastric gavage and, ghrelin (20 µg/kg/day) was given intraperitoneally for 5 weeks. Plasma-S-sulfonate level was increased in S and SG groups. Na2S2O5 administration significantly elevated total oxidant status (TOS) levels while depleting total antioxidant status (TAS) levels in gastric mucosa. Ghrelin significantly decreased gastric TOS levels in the SG group compared with the S group. Additionally, TAS levels were found to be higher in SG group in reference to S group. Na2S2O5 administration also markedly increased the number of apoptotic cells, cleaved caspase-3 and PAR expression (PARP activity indicator) and, decreased Ki67 expression (cell proliferation index) in gastric mucosal cells. Ghrelin treatment decreased the number apoptotic cells, cytochrome C release, PAR and, caspase-3 expressions while increasing Ki67 expression in gastric mucosa exposed to Na2S2O5. In conclusion, we suggest that ghrelin treatment might ameliorate ingested-Na2S2O5 induced gastric mucosal injury stemming from apoptosis and oxidative stress in rats.

Merit of quinacrine in the decrease of ingested sulfite-induced toxic action in rat brain.

We aimed at investigating the effects of sulfite-induced lipid peroxidation and apoptosis mediated by secretory phospholipase A2 (sPLA2) on somatosensory evoked potentials (SEP) alterations in rats. Thirty male albino Wistar rats were randomized into three experimental groups as follows; control (C), sodium metabisulfite treated (S), sodium metabisulfite+quinacrine treated (SQ). Sodium metabisulfite (100 mg/kg/day) was given by gastric gavage for 5 weeks and 10 mg/kg/day quinacrine was applied as a single dose of intraperitoneal injection for the same period. The latencies of SEP components were significantly prolonged in the S group and returned to control levels following quinacrine administration. Plasma-S-sulfonate level was increased in S and SQ groups. TBARS levels in the S group were significantly higher than those detected in controls. Quinacrine significantly decreased brain TBARS levels in the SQ group compared with the S group. Quinacrine treatment did not have an effect on the increased sPLA2 level of the sulfite administered group. Immunohistochemistry showed that sulfite caused an increase in caspase-3 and TUNEL positive cells, restored to control levels via quinacrine administration. This study showed that sPLA2 might play a role in ingested sulfite-induced SEP alterations, oxidative stress, apoptotic cell death and DNA damage in the brain.