Thymoquinone attenuates diethylnitrosamine induction of hepatic carcinogenesis through antioxidant signaling

Hepatocellular carcinoma accounts for about 80–90% of all liver cancer and is the fourth most common cause of cancer mortality. Although there are many strategies for the treatment of liver cancer, chemoprevention seems to be the best strategy for lowering the incidence of this disease. Therefore, this study has been initiated to investigate whether thymoquinone (TQ), Nigella sativa derived-compound with strong antioxidant properties, supplementation could prevent initiation of hepatocarcinogenesis-induced by diethylnitrosamine (DENA), a potent initiator and hepatocarcinogen, in rats. Male Wistar albino rats were divided into four groups. Rats of Group 1 received a single intraperitoneal (I.P.) injection of normal saline. Animals in Group 2 were given TQ (4 mg/kg/day) in drinking water for 7 consecutive days. Rats of Group 3 were injected with a single dose of DENA (200 mg/kg, I.P.). Animals in Group 4 were received TQ and DENA. DENA significantly increased alanine transaminase (ALT), alkaline phosphatase (ALP), total bilirubin, thiobarbituric acid reactive substances (TBARS) and total nitrate/nitrite (NOx) and decreased reduced glutathione (GSH), glutathione peroxidase (GSHPx), glutathione-s-transferase (GST) and catalase (CAT) activity in liver tissues. Moreover, DENA decreased gene expression of GSHPx, GST and CAT and caused severe histopathological lesions in liver tissue. Interestingly, TQ supplementation completely reversed the biochemical and histopathological changes induced by DENA to the control values. In conclusion, data from this study suggest that: (1) decreased mRNA expression of GSHPx, CAT and GST during DENA-induced initiation of hepatic carcinogenesis, (2) TQ supplementation prevents the development of DENA-induced initiation of liver cancer by decreasing oxidative stress and preserving both the activity and mRNA expression of antioxidant enzymes.

Naringenin neutralises oxidative stress and nerve growth factor discrepancy in experimental diabetic neuropathy

OBJECTIVES

Present study aims to investigate the ameliorative effects of naringenin (NG) on experimentally induced diabetic neuropathy (DN) in rats.

METHODS

Diabetes was induced by single intraperitoneal injection of streptozotocin (STZ, 60  g/kg). Naringenin (25 and 50 mg/kg/day) treatment was started 2 weeks after the diabetes induction and continued for five consecutive weeks. Pain threshold behaviour tests were performed at the end of the treatment. Serum levels of glucose, insulin and pro-inflammatory cytokines were assessed. In sciatic tissues, markers oxidative stress, cytokines and neurotrophic factors were measured.

RESULTS

NG treatments showed significant decrease in paw-withdrawal (P < 0.01) and tail-flick latency (P < 0.01). The drug attenuated the diabetic-induced changes in serum glucose, insulin and pro-inflammatory cytokines including tumour necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta) and interleukin-6 (IL-6). In sciatic nerve, the diabetic-induced alterations in interleukins and oxidative stress biomarkers were significantly attenuated by NG. Decreased sciatic expressions of insulin growth factor (IGF) and nerve growth factor (NGF) in diabetic rats were also ameliorated by NG. Diabetes-induced dysregulated levels of nitric oxide (NO), thiobarbituric acid reactive substances (TBARS), reduced glutathione (GSH), activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR) were ameliorated by NG. Histological analysis showed that NG corrected the altered sciatic changes in diabetic animals.

DISCUSSION

We suggest that neuro-protective effect of NG molecules in sciatic nerve of diabetic rats, through its anti-diabetic as well as antioxidant and anti-inflammatory properties.

Telmisartan inhibits hyperalgesia and inflammatory progression in a diabetic neuropathic pain model of Wistar rats

Objective:

To evaluate the potential therapeutic value of telmisartan (TMT) against diabetic neuropathy (DN) and associated pain in Wistar rats.

Methods:

Peripheral DN was induced by a single intraperitoneal streptozotocin injection (55 mg/kg), and 3 weeks later TMT treatment was started (5 and 10 mg/kg/day), and continued for 4 weeks. Mechanical nociceptive threshold, motor coordination, and thermal nociceptive threshold tests were performed before and after TMT treatment. In serum, glucose, pro-inflammatory cytokines including tumor necrosis factor-α, interleukin-1β, and interleukin-6 were assessed. Nerve growth factor (NGF) levels and histopathological changes were estimated in the sciatic nerve. This study was conducted at the Experimental Animal Care Center, Department of Pharmacology, College of Pharmacy, King Saud University, Riyadh, Kingdom of Saudi Arabia between January 2013 and May 2014.

Results:

We observed a significant reduction in mechanical nociceptive threshold, motor coordination, and thermal nociceptive threshold in diabetic animals. The TMT treatment significantly enhanced the reduced mechanical nociceptive threshold. The untreated diabetic animals revealed a significant decrease in sciatic NGF, which was markedly attenuated by TMT. The elevated serum levels of cytokines in diabetic animals were inhibited by the TMT treatments. Histopathological evaluation showed obvious nerve degeneration in the diabetic group that was eliminated in the TMT treated diabetic groups.

Conclusion:

Telmisartan has a potential neuro-protective effect on peripheral DN; this is mediated through its anti-inflammatory effects and its dual properties as an angiotensin receptor blocker, and a partial peroxisome proliferator activator receptor-g ligand.

Pretreatment of Gymnema sylvestre revealed the protection against acetic acid-induced ulcerative colitis in rats

Background

Overproduction of free radicals and decreased antioxidant capacity are well-known risk factors for inflammatory bowel diseases. Gymnema sylvestre (GS) leaves extract is distinguished for its anti-diabetic, antioxidant and anti-inflammatory properties. Present study is designed to evaluate the preventative activities of GS against acetic acid (AA)-induced ulcerative colitis in Wistar rats.

Methods

Experimentally ulcerative colitis (UC) was induced by AA in animals pretreated with three different doses of GS leaves extract (50, 100, 200 mg/kg/day) and a single dose of mesalazine (MES, 300 mg/kg/day) for seven days. Twenty four hours later, animals were sacrificed and the colonic tissues were collected. Colonic mucus content was determined using Alcian blue dye binding technique. Levels of thiobarbituric acid reactive substances (TBARS), total glutathione sulfhydryl group (T-GSH) and non-protein sulfhydryl group (NPSH) as well as the activity of the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) were estimated in colon tissues. Colonic nucleic acids (DNA and RNA) and total protein (TP) concentrations were also determined. Levels of pro-inflammatory cytokines including interleukin-1 beta (IL-1β), tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) as well as prostaglandin E₂ (PGE₂) and nitric oxide (NO) were estimated in colonic tissues. The histopathological changes of the colonic tissues were also observed.

Results

In AA administered group TBARS levels were increased, while colonic mucus content, T-GSH and NP-SH, SOD and CAT were reduced in colon. Pretreatment with GS inhibited TBARS elevation as well as mucus content, T-GSH and NP-SH reduction. Enzymatic activities of SOD and CAT were brought back to their normal levels in GS pretreated group. A significant reduction in DNA, RNA and TP levels was seen following AA administration and this inhibition was significantly eliminated by GS treatment. GS pretreatment also inhibited AA-induced elevation of pro-inflammatory cytokines, PGE₂ and NO levels in colon. The apparent UC protection was further confirmed by the histopathological screening.

Conclusion

The GS leaves extract showed significant amelioration of experimentally induced colitis, which may be attributed to its anti-inflammatory and antioxidant property.

Protective effect of rutin on the antioxidant genes expression in hypercholestrolemic male Westar rat

Background

High-cholesterol diet (HCD) increases the oxidative stress in different tissues leading to many diseases. Rutin (RT) is a natural flavonoid (vitamin p), which possesses an antioxidant activity with protective potential. The present study aimed to examine the potential effects of rutin on hypercholesterolemia-induced hepatotoxicity in rat.

Methods

Male Wistar rats were divided into four groups: GI) control (Rat chow), GII) Rutin (0.2% in rat chow), GIII) HCD (1% cholesterol and 0.5% cholic acid in rat chow) and GIV) rutin (0.2%) + HCD.

Results

Rutin in combination with HCD induced a significant protective effect against the hepatotoxicity by reducing the plasma level of alanine transaminase (ALT), aspartate aminotransferase (AST), triglyceride (TG), total cholesterol (TC), and low-density lipoprotein (LDL). The HCD (GII) showed a decrease in glutathione peroxidase (GPx), glutathione reductase (GR) and increase in glutathione S transferase α (GSTα), sulfiredoxin-1(Srx1), glutamate-cysteine ligase (GCL) and paraoxonase-1(PON-1) genes expression levels.

Conclusion

Treatment with rutin reversed all the altered genes induced by HCD nearly to the control levels. The present study concluded that the HCD feedings altered the expression levels of some genes involved in the oxidative stress pathway resulting in DNA damage and hepatotoxicity. Rutin have a hepatoprotective effect through the mechanism of enhancing the antioxidant effect via amelioration of oxidative stress genes.

Possible biochemical effects following inhibition of ethanol-induced gastric mucosa damage by Gymnema sylvestre in male Wistar albino rats

CONTEXT

Gymnema sylvestre (GS) R. Br. (Gymnema) (Asclepiadaceae) has been used from ancient times as a folk medicine for the treatment of diabetes, obesity, urinary disorder, and stomach stimulation.

OBJECTIVE

The present study was designed to investigate the effects of G. sylvestre leaves ethanol extract on gastric mucosal injury in rats.

MATERIALS AND METHODS

Gastric mucosal damage was induced by 80% ethanol in 36 h fasted rats. The effect of G. sylvestre on gastric secretions induced in Shay rats was estimated. In stomach, wall mucus, non-protein sulfhydryl groups (NP-SH), malondialdehyde (MDA), total proteins and nucleic acids levels were estimated. Histopathological changes were observed.

RESULTS

G. sylvestre pretreatment at doses of 100, 200 and 400 mg/kg provided 27, 49, and 63% protection against the ulcerogenic effect of ethanol, respectively. Pylorus ligation accumulated 10.24 mL gastric secretions with 66.56 mEq of acidity in control rats. Pretreatment with G. sylvestre significantly inhibited the secretions volume and acidity in dose-dependent manner. Ethanol caused significant depletion in stomach-wall mucus (p < 0.001), total proteins (p < 0.01), nucleic acids (p < 0.001), and NP-SH (p < 0.001) levels. Pretreatment with G. sylvestre showed protection against these depleted levels in dose-dependent manner. The MDA levels increased from 19.02 to 29.22 nmol/g by ethanol ingestion and decreased with G. sylvestre pretreatments in dose-dependent manner.

CONCLUSION

The protective effect of G. sylvestre observed in the present study is attributed to its effect on mucus production, increase in nucleic acid and NP-SH levels, which appears to be mediated through its free radical scavenging ability and/or possible cytoprotective properties.

Protective efficacy of immunoglobulins Y prepared against Cerastes cerastes snake venom in the Kingdom of Saudi Arabia

OBJECTIVES

To prepare and evaluate the protective efficacy of immunoglobulin Y (IgY) prepared against local Saudi Cerastes cerastes snake venom.

METHODS

The study was conducted between October 2009 and October 2011 at the Center of Excellence in Biotechnology Research, King Saud University, Riyadh, Kingdom of Saudi Arabia. The study designed as follow; 4 groups of 8 chickens were immunized intramuscularly with Cerastes cerastes snake venoms mixed with Freund's complete adjuvant. Three weeks later, the injections were repeated with the venoms with incomplete Freund's adjuvant. Three boosters were given with the venoms at 3 weeks intervals. The IgY was extracted by ammonium sulphate-caprylic acid method, the antibody titer were tested by enzyme linked immunosorbant assay, and the protective efficacies of the extracted immunoglobulins were performed.

RESULTS

Immunoglobulin Y preparation extracted by ammonium sulphate-caprylic acid method showed lack of low molecular weight bands. The bands representing IgY-antibodies, which have molecular weights ranged from 180-200 KD, appeared sharp and clear. Furthermore, evaluation of the prepared protective value of IgY-antibodies revealed one ml of extracted IgY-antibodies containing 15 mg/ml anti Cerastes cerastes; specific IgY could produce 100% protection against 50 LD50.

CONCLUSION

Laying hens could be used as an alternative source of polyclonal antibodies against Cerastes cerastes snake venoms due to several advantages as compared with mammals.

Post-learning REM sleep deprivation impairs long-term memory: reversal by acute nicotine treatment

Rapid eye movement sleep deprivation (REM-SD) is associated with spatial learning and memory impairment. During REM-SD, an increase in nicotine consumption among habitual smokers and initiation of tobacco use by non-smokers have been reported. We have shown recently that nicotine treatment prevented learning and memory impairments associated with REM-SD. We now report the interactive effects of post-learning REM-SD and/or nicotine. The animals were first trained on the radial arm water maze (RAWM) task, then they were REM-sleep deprived using the modified multiple platform paradigm for 24h. During REM-SD period, the rats were injected with saline or nicotine (1mg/kg s.c. every 12h: a total of 3 injections). The animals were tested for long-term memory in the RAWM at the end of the REM-SD period. The 24h post-learning REM-SD significantly impaired long-term memory. However, nicotine treatment reversed the post-learning REM-SD-induced impairment of long-term memory. On the other hand, post-learning treatment of normal rats with nicotine for 24h enhanced long-term memory. These results indicate that post-learning acute nicotine treatment prevented the deleterious effect of REM-SD on cognitive abilities.

Sleep deprivation prevents stimulation-induced increases of levels of P-CREB and BDNF: protection by caffeine

It is well known that caffeine and sleep deprivation have opposing effects on learning and memory; therefore, this study was undertaken to determine the effects of chronic (4wks) caffeine treatment (0.3g/l in drinking water) on long-term memory deficit associated with 24h sleep deprivation. Animals were sleep deprived using the modified multiple platform method. The results showed that chronic caffeine treatment prevented the impairment of long-term memory as measured by performance in the radial arm water maze task and normalized L-LTP in area CA1 of the hippocampi of sleep-deprived anesthetized rats. Sleep deprivation prevents the high frequency stimulation-induced increases in the levels of phosphorylated-cAMP response element binding protein (P-CREB) and brain-derived neurotrophic factor (BDNF) seen during the expression of late phase long-term potentiation (L-LTP). However, chronic caffeine treatment prevented the effect of sleep-deprivation on the stimulated levels of P-CREB and BDNF. The results suggest that chronic caffeine treatment may protect the sleep-deprived brain probably by preserving the levels of P-CREB and BDNF.

Design, synthesis and biological evaluation of novel quinazoline derivatives as potential antitumor agents: molecular docking study

Novel derivatives of quinazoline (1-27) have been synthesized and tested for their antitumor activity against three tumor cell lines among these cell lines the human breast carcinoma cell line (MCF-7) in which EGFR is highly expressed. All tested compounds showed potent and selective activity against breast cancer (MCF-7) with IC(50) range of 3.35-6.81 microg/ml. With regarding broad-spectrum activity compounds 5, 9, 15, 18 and 20 exploited potent antitumor against human liver cell line (HEPG2), human breast cell line (MCF-7) and human cervix cell line (HELA) with IC(50) range of 3.35-5.59 microg/ml. Virtual screening was carried out through docking the designed compounds into the ATP binding site of epidermal growth factor receptor (EGFR) to predict if these compounds have analogous binding mode to the EGFR inhibitors.

Acute nicotine treatment prevents REM sleep deprivation-induced learning and memory impairment in rat

Rapid eye movement (REM) sleep deprivation (SD) is implicated in impairment of spatial learning and memory and hippocampal long-term potentiation (LTP). An increase in nicotine consumption among habitual smokers and initiation of tobacco use by nonsmokers was observed during SD. Although nicotine treatment was reported to attenuate the impairment of learning and memory and LTP associated with several mental disorders, the effect of nicotine on SD-induced learning and memory impairment has not been studied. Modified multiple platform paradigm was used to induce SD for 24 or 48 h during which rats were injected with saline or nicotine (1 mg kg(-1) s.c.) twice a day. In the radial arm water maze (RAWM) task, 24- or 48-h SD significantly impaired learning and short-term memory. In addition, extracellular recordings from CA1 and dentate gyrus (DG) regions of the hippocampus in urethane anesthetized rats showed a significant impairment of LTP after 24- and 48-h SD. Treatment of normal rats with nicotine for 24 or 48 h did not enhance spatial learning and memory or affect magnitude of LTP in the CA1 and DG regions. However, concurrent, acute treatment of rats with nicotine significantly attenuated SD-induced impairment of learning and STM and prevented SD-induced impairment of LTP in the CA1 and DG regions. These results show that acute nicotine treatment prevented the deleterious effect of sleep loss on cognitive abilities and synaptic plasticity.

Chronic caffeine treatment prevents sleep deprivation-induced impairment of cognitive function and synaptic plasticity

STUDY OBJECTIVES

This study was undertaken to provide a detailed account of the effect of chronic treatment with a small dose of caffeine on the deleterious effects of sleep loss on brain function in rats.

EXPERIMENTAL DESIGN

We investigated the effects of chronic (4 weeks) caffeine treatment (0.3 g/L in drinking water) on memory impairment in acutely (24 h) sleep-deprived adult male Wistar rats. Sleep deprivation was induced using the modified multiple platform model. The effects of caffeine on sleep deprivation-induced hippocampus-dependent learning and memory deficits were studied by 3 approaches: learning and memory performance in the radial arm water maze task, electrophysiological recording of early long-term potentiation (E-LTP) in area CA1 of the hippocampus, and levels of memory- and synaptic plasticity-related signaling molecules after E-LTP induction.

MEASUREMENT AND RESULTS

The results showed that chronic caffeine treatment prevented impairment of hippocampus-dependent learning, shortterm memory and E-LTP of area CA1 in the sleep-deprived rats. In correlation, chronic caffeine treatment prevented sleep deprivation-associated decrease in the levels of phosphorylated calcium/calmodulin-dependent protein kinase II (P-CaMKII) during expression of E-LTP.

CONCLUSIONS

The results suggest that long-term use of a low dose of caffeine prevents impairment of short-term memory and E-LTP in acutely sleep-deprived rats.

Carnitine deficiency aggravates cyclophosphamide-induced cardiotoxicity in rats

BACKGROUND

This study examined, for the first time, the involvement of carnitine deficiency in cardiotoxicity, particularly cyclophosphamide (CP)-induced cardiomyopathy, as well as effects of carnitine supplementation with propionyl-L-carnitine (PLC) on cardiotoxicity.

METHODS

An animal model of carnitine deficiency was developed in rats treated with D-carnitine (DC)-mildronate (MD). Adult male Wistar albino rats were assigned to one of six treatment groups: the first three groups were injected intraperitoneally with normal saline, PLC (250 mg/kg/day), and DC (250 mg/kg/day) combined with MD (200 mg/kg/day), respectively, for 10 successive days. In groups 4-6, the same doses of normal saline, PLC and DC-MD were injected, respectively, during the 5 successive days before and after a single dose of CP (200 mg/kg). On day 6 after CP treatment, 24-hour urine was collected, then animals were sacrificed, and serum as well as hearts were isolated.

RESULTS

CP caused a significant increase in serum creatine phosphokinase isoenzyme (CK-MB), lactate dehydrogenase (LDH), urinary carnitine excretion and clearance and intramitochondrial acetyl-CoA/CoA-SH, and a significant decrease in serum free carnitine, total carnitine and adenosine triphosphate (ATP) contents in cardiac tissue. In the carnitine-depleted rats, CP induced dramatic increases in CK-MB and LDH levels, carnitine clearance and intramitochondrial acetyl-CoA/CoA-SH, as well as progressive reduction in total carnitine and ATP in cardiac tissues. Interestingly, PLC supplementation completely reversed the biochemical and histopathological changes induced by CP to the control values.

CONCLUSION

(1) Carnitine deficiency is a risk factor which is involved in CP-related cardiomyopathy; (2) serum and urinary carnitine levels should be monitored and viewed as indices of CP-induced multiple organ toxicity, and (3) carnitine supplementation, using PLC, prevents the development of CP-induced cardiotoxicity.

Increased urinary losses of carnitine and decreased intramitochondrial coenzyme A in gentamicin-induced acute renal failure in rats

BACKGROUND

This study examined whether carnitine deficiency is a risk factor and should be viewed as a mechanism during the development of gentamicin (GM)-induced ARF as well as exploring if carnitine supplementation could offer protection against this toxicity.

METHODS

Adult male Wistar albino rats were assigned to one of six treatment groups: group 1 (control) rats were given daily intraperitoneal (I.P.) injections of normal saline for 8 consecutive days; groups 2, 3 and 4 rats were given GM (80 mg/kg/day, I.P.), l-carnitine (200 mg/kg/day, I.P.) and d-carnitine (250 mg/kg/day, I.P.), respectively, for 8 consecutive days. Rats of group 5 (GM plus d-carnitine) received a daily I.P. injection of d-carnitine (250 mg/kg/day) 1 h before GM (80 mg/kg/day) for 8 consecutive days. Rats of group 6 (GM plus l-carnitine) received a daily I.P. injection of l-carnitine (200 mg/kg/day) 1 h before GM (80 mg/kg/day) for 8 consecutive days.

RESULTS

GM significantly increased serum creatinine, blood urea nitrogen (BUN), urinary carnitine excretion, intramitochondrial acetyl-CoA and total nitrate/nitrite (NOx) and thiobarbituric acid reactive substances (TBARS) in kidney tissues and significantly decreased total carnitine, intramitochondrial CoA-SH, ATP, ATP/ADP and reduced glutathione (GSH) in kidney tissues. In carnitine-depleted rats, GM caused a progressive increase in serum creatinine, BUN and urinary carnitine excretion and a progressive decrease in total carnitine, intamitochondrial CoA-SH and ATP. Interestingly, l-carnitine supplementation resulted in a complete reversal of the increase in serum creatinine, BUN, urinary carnitine excretion and the decrease in total carnitine, intramitochondrial CoA-SH and ATP, induced by GM, to the control values. Moreover, the histopathological examination of kidney tissues confirmed the biochemical data, where l-carnitine prevents and d-carnitine aggravates GM-induced ARF.

CONCLUSIONS

(i) GM-induced nephrotoxicity leads to increased urinary losses of carnitine; (ii) carnitine deficiency is a risk factor and should be viewed as a mechanism during the development of GM-induced ARF; and (iii) carnitine supplementation ameliorates the severity of GM-induced kidney dysfunction by increasing the intramitochondrial CoA-SH/acetyl-CoA ratio and ATP production.

Chronic nicotine restores normal Aβ levels and prevents short-term memory and E-LTP impairment in Aβ rat model of Alzheimer's disease

Alzheimer's disease (AD) is a devastating neurodegenerative disorder characterized by increased deposition of beta-amyloid (Aβ) peptides and progressive cholinergic dysfunction in regions of the brain involved in learning and memory processing. In AD, progressive accumulation of Aβ peptide impairs nicotinic acetylcholine receptor (nAChR) function by an unknown mechanism believed to involve α(7)- and α(4)β(2)-nAChR blockade. The three approaches of the current study evaluated the effects of chronic nicotine treatment in the prevention of Aβ-induced impairment of learning and short-term memory. Rat AD model was induced by 14-day i.c.v. osmotic pump infusion of a 1:1 mixture of 300 pmol/day Aβ(1-40)/Aβ(1-42) or Aβ(40-1) (inactive peptide, control). The effect of nicotine (2 mg/(kg day)) on Aβ-induced spatial learning and memory impairments was assessed by evaluation of performance in the radial arm water maze (RAWM), in vivo electrophysiological recordings of early-phase long-term potentiation (E-LTP) in urethane-anesthetized rats, and immunoblot analysis to determine changes in the levels of beta-site amyloid precursor protein (APP)-cleaving enzyme (BACE), Aβ and memory-related proteins. The results indicate that 6 weeks of nicotine treatment reduced the levels of Aβ(1-40) and BACE1 peptides in hippocampal area CA1 and prevented Aβ-induced impairment of learning and short-term memory. Chronic nicotine also prevented the Aβ-induced inhibition of basal synaptic transmission and LTP in hippocampal area CA1. Furthermore, chronic nicotine treatment prevented the Aβ-induced reduction of α(7)- and α(4)-nAChR. These effects of nicotine may be due, at least in part, to upregulation of brain derived neurotropic factor (BDNF).

Pro-inflammatory and oxidative stress pathways which compromise sperm motility and survival may be altered by L-carnitine

The testis is an immunologically privileged organ. Sertoli cells can form a blood-testis barrier and protect sperm cells from self-immune system attacks. Spermatogenesis may be inhibited by severe illness, bacterial infections and chronic inflammatory diseases but the mechanism(s) is poorly understood. Our objective is to help in understanding such mechanism(s) to develop protective agents against temporary or permanent testicular dysfunction. Lipopolysaccaride (LPS) is used as a model of animal sepsis while L-carnitine (LCR) is used as a protective agent. A total of 60 male Swiss albino rats were divided into four groups (15/group). The control group received Saline; the 2(nd) group was given LCR (500 mg/kg i.p, once). The third group was treated with LPS (5 mg/kg i.p once) and the fourth group received LCR then LPS after three hours. From each group, five rats were used for histopathological examination. Biochemical parameters were assessed in the remaining ten rats. At the end of the experiment, animals were lightly anaesthetized with ether where blood samples were collected and testes were dissected on ice. Sperm count and motility were evaluated from cauda epididymis in each animal. Also, oxidative stress was evaluated by measuring testicular contents of reduced glutathione (GSH), malondialdehyde (MDA) and 8-hydroxydeoxyguanosine (8-HDG, the DNA adduct for oxidative damage) in testicular DNA. The pro-inflammatory mediator nitric oxide (NO) in addition to lactate dehydrogenase (LDHx) isoenzyme-x activity as an indicator for normal spermatozoal metabolism were assessed in testicular homogenate. Serum interlukin (IL)-2 level was also assessed as a marker for T-helper cell function. The obtained data revealed that LPS induced marked reductions in sperm's count and motility, obstruction in seminiferous tubules, hypospermia and dilated congested blood vessels in testicular sections concomitant with decreased testicular GSH content and LDHx activity. Moreover, the testicular levels of MDA, 8-HDG (in testicular DNA) and NO as well as serum IL-2 level were increased. Administration of LCR before LPS returned both sperm count and motility to normal levels. Also, contents of testicular GSH, MDA, 8-HDG and NO returned back to the corresponding control values. In addition, serum IL-2 level as well as histological abnormalities were markedly improved in LCR + LPS-treated rats. In conclusion, LPS increased proinflammatory and oxidative stress markers in the testis leading to a marked testicular dysfunction. L-carnitine administration ameliorates these effects by antioxidant and/or anti-inflammatory mechanisms suggesting a protective role against male infertility in severely infected or septic patients.

Progression of diethylnitrosamine-induced hepatic carcinogenesis in carnitine-depleted rats

AIM: To investigate whether carnitine deficiency is a risk factor during the development of diethylnitrosamine (DENA)-induced hepatic carcinogenesis.

METHODS: A total of 60 male Wistar albino rats were divided into six groups with 10 animals in each group. Rats in group 1 (control group) received a single intraperitoneal (i.p.) injection of normal saline. Animals in group 2 (carnitine-supplemented group) were given L-carnitine (200 mg/kg per day) in drinking water for 8 wk. Animals in group 3 (carnitine-depleted group) were given D-carnitine (200 mg/kg per day) and mildronate (200 mg/kg per day) in drinking water for 8 wk. Rats in group 4 (DENA group) were injected with a single dose of DENA (200 mg/kg, i.p.) and 2 wk later received a single dose of carbon tetrachloride (2 mL/kg) by gavage as 1:1 dilution in corn oil. Animals in group 5 (DENA-carnitine depleted group) received the same treatment as group 3 and group 4. Rats in group 6 (DENA-carnitine supplemented group) received the same treatment as group 2 and group 4.

RESULTS: Administration of DENA resulted in a significant increase in alanine transaminase (ALT), gamma-glutamyl transferase (G-GT), alkaline phosphatase (ALP), total bilirubin, thiobarbituric acid reactive substances (TBARS) and total nitrate/nitrite (NOx) and a significant decrease in reduced glutathione (GSH), glutathione peroxidase (GSHPx), catalase (CAT) and total carnitine content in liver tissues. In the carnitine-depleted rat model, DENA induced a dramatic increase in serum ALT, G-GT, ALP and total bilirubin, as well as a progressive reduction in total carnitine content in liver tissues. Interestingly, L-carnitine supplementation resulted in a complete reversal of the increase in liver enzymes, TBARS and NOx, and a decrease in total carnitine, GSH, GSHPx, and CAT induced by DENA, compared with the control values. Histopathological examination of liver tissues confirmed the biochemical data, where L-carnitine prevented DENA-induced hepatic carcinogenesis while D-carnitine-mildronate aggravated DENA-induced hepatic damage.

CONCLUSION: Data from this study suggest for the first time that: (1) carnitine deficiency is a risk factor and should be viewed as a mechanism in DENA-induced hepatic carcinogenesis; (2) oxidative stress plays an important role but is not the only cause of DENA-induced hepatic carcinogenesis; and (3) long-term L-carnitine supplementation prevents the development of DENA-induced liver cancer.

Molecular cytogenetic evaluation of the mechanism of micronuclei formation induced by camptothecin, topotecan, and irinotecan

We used the conventional bone marrow micronucleus test complemented with the fluorescent in situ hybridization with the minor satellite DNA probe to investigate the mechanisms of induction of micronuclei in mice treated with camptothecin and its clinical antineoplastic analogues topotecan and irinotecan. All experiments were performed with male Swiss albino mice. Single doses of 1 mg/kg camptothecin or 0.6 mg/kg topotecan were injected intraperitoneally and bone marrow was sampled at 30 hr (camptothecin) or 24 hr (topotecan) after treatment. A dose of 60 mg/kg irinotecan was injected intravenously, once every fourth day for 13 days and bone marrow was sampled 24 hr after the last treatment. In animals treated with camptothecin, a total of 1.07% micronuclei were found and 70% of them were centromere-negative, indicating their formation by DNA strand breaks and reflecting the predominant clastogenic activity of camptothecin. Exposure to topotecan and irinotecan yielded 1.71 and 0.83% micronuclei, respectively. About 52.7 and 48.8% of the induced micronuclei, respectively, were centromere-positive, indicating their formation by whole chromosomes and reflecting the aneugenic activity of both compounds. Correspondingly, about 47.3 and 51.2% of the induced micronuclei, respectively were centromere-negative, demonstrating that topotecan and irinotecan not only induce chromosome loss but also DNA strand breaks. Both the clastogenic and aneugenic potential of these drugs can lead to the development of secondary tumors and abnormal reproductive outcomes. Therefore, the clinical use of these agents must be weighed against the risks of secondary malignancies in cured patients and persistent genetic damage of their potential offspring.

Metallothionein induction reduces caspase-3 activity and TNFalpha levels with preservation of cognitive function and intact hippocampal neurons in carmustine-treated rats

Hippocampal integrity is essential for cognitive functions. On the other hand, induction of metallothionein (MT) by ZnSO(4) and its role in neuroprotection has been documented. The present study aimed to explore the effect of MT induction on carmustine (BCNU)-induced hippocampal cognitive dysfunction in rats. A total of 60 male Wistar albino rats were randomly divided into four groups (15/group): The control group injected with single doses of normal saline (i.c.v) followed 24 h later by BCNU solvent (i.v). The second group administered ZnSO(4) (0.1 micromol/10 microl normal saline, i.c.v, once) then BCNU solvent (i.v) after 24 h. Third group received BCNU (20 mg/kg, i.v, once) 24 h after injection with normal saline (i.c.v). Fourth group received a single dose of ZnSO(4) (0.1 micromol/10 microl normal saline, i.c.v) then BCNU (20 mg/kg, i.v, once) after 24 h. The obtained data revealed that BCNU administration resulted in deterioration of learning and short-term memory (STM), as measured by using radial arm water maze, accompanied with decreased hippocampal glutathione reductase (GR) activity and reduced glutathione (GSH) content. Also, BCNU administration increased serum tumor necrosis factor-alpha (TNFalpha), hippocampal MT and malondialdehyde (MDA) contents as well as caspase-3 activity in addition to histological alterations. ZnSO(4) pretreatment counteracted BCNU-induced inhibition of GR and depletion of GSH and resulted in significant reduction in the levels of MDA and TNFalpha as well as the activity of caspase-3. The histological features were improved in hippocampus of rats treated with ZnSO(4) + BCNU compared to only BCNU-treated animals. In conclusion, MT induction halts BCNU-induced hippocampal toxicity as it prevented GR inhibition and GSH depletion and counteracted the increased levels of TNFalpha, MDA and caspase-3 activity with subsequent preservation of cognition.

Levothyroxin restores hypothyroidism-induced impairment of hippocampus-dependent learning and memory: Behavioral, electrophysiological, and molecular studies

Hypothyroidism induces cognitive impairment in experimental animals and patients. Clinical reports are conflicting about the ability of thyroid hormone replacement therapy to fully restore the hypothyroidism-induced learning and memory impairment. In this study, we investigated the effects of L-thyroxin (thyroxin) treatment on hippocampus-dependent learning and memory in thyroidectomized adult rats. In the radial arm water maze (RAWM) task, thyroxin treated thyroidectomized animals made significantly fewer errors than the untreated hypothyroid animals in Trial 3 of the acquisition phase, short-term memory and long-term memory tests. In addition, the number of errors made by the thyroxin treated thyroidectomized animals was not different from that of the control group. Furthermore, the days-to-criterion (DTC) values for thyroxin treated thyroidectomized animals were not different from those of the control group but significantly lower than those of the untreated hypothyroid animals. In anesthetized rats, extracellular recording from hippocampal area CA1 of hypothyroid rats shows that thyroxin treatment restores impaired Late-phase long-term potentiation (L-LTP). Immunoblot analysis of signaling molecules, including cyclic-AMP response element binding protein (CREB), mitogen-activated protein kinases (MAPKp44/42; ERK1/2), in area CA1 revealed that thyroxin treatment reversed hypothyroidism-induced reduction of signaling molecules essential for learning and memory, and L-LTP. This study shows that thyroxin treatment reverses hypothyroidism-induced impairment of hippocampus-dependent cognition, and L-LTP, probably by restoring the levels of signaling molecule important for these processes.

Superoxide anion stress attenuates the contractile response of the Guinea pig vas deferens to ATP and diadenosine tetraphosphate. Possible effect on calcium dysregulation

Induction of endogenous superoxide anion stress by the use of the superoxide dismutase inhibitor diethylthiocarbamate (DETCA; 10 mmol/l) produced a potent inhibition of the ATP (0.3-10 mmol/l) and diadenosine tetraphosphate (AP(4)A) contractile activity in the isolated vas deferens by 29-92 and 24-90%, respectively. Pyrogallol (0.1 mmol/l), the exogenous superoxide anion generator, produced a significant inhibition on the contractile activity of the vas deferens induced by ATP and AP(4)A by 33-89 and 25-82%, respectively. DETCA (10 mmol/l) and pyrogallol (0.1 mmol/l) attenuated the contractile response of isolated guinea pig vas deferens strips to the selective P2X agonist alpha,beta-methyleneATP (alpha,beta-meATP; 50 micromol/l) by 25 and 47%, respectively. In Ca(2+)-free high-K(+) (80 mmol/l) Krebs solution, pyrogallol and DETCA produced inhibition of the contractile response to alpha,beta-meATP (50 micromol/l) in similar way to that in normal Krebs solution. The further addition of CaCl(2) (1 mmol/l) abolished the inhibitory effects exerted by pyrogallol and DETCA. The control contractile response to alpha,beta-meATP (50 micromol/l) was not affected in Ca(2+)-free high-K(+) (80 mmol/l) Krebs solution. It may be concluded that superoxide anion stress produces a significant inhibitory effect on both mono- and di-nucleotide purinergic contraction of the vas deferens. Superoxide anion appears to interrupt the P2X(1)-mediated transduction cascade at some step(s) of intracellular calcium handling.

In vivo expression of ganglionic long-term potentiation in superior cervical ganglia from hypertensive aged rats

Sustained increase in central sympathetic outflow to ganglia may provide the repeated high frequency presynaptic activity required for induction of long-term potentiation in sympathetic ganglia (gLTP), which is known to be involved in the manifestation of a neurogenic form of hypertension, namely stress-hypertension. Aging is often viewed as a progressive decline in physiological competence with a corresponding impaired ability to adapt to stressful stimuli. Old animals have exaggerated sympathetic activity as well as increased morbidity and mortality during prolonged exposure to stressful stimuli. Using the superior cervical ganglion (SCG) as a model for sympathetic ganglia, electrophysiological and biochemical evidence show that mildly hypertensive aged rats (22-month old) have expressed gLTP in vivo. This is suggested by a number of lines of evidence. Firstly, a shift in input/output (I/O) curve of ganglia from aged rats to the left side of I/O curve of ganglia from 6-month old (adult) rats indicating expression of gLTP. Secondly, failure of in vitro high frequency stimulation to induce gLTP in ganglia isolated from aged rats, which indicates occlusion due to saturation, which, in turn, suggests in vivo expression of gLTP in these ganglia. Thirdly, in vitro inhibition of basal ganglionic transmission by blockers of gLTP (5-HT(3) antagonists) is observed in ganglia isolated from aged rats, but not in those from adult rats. Finally, immunoblot analysis revealed that protein levels of signaling molecules such as calcium-calmodulin kinase II (CaMKII; phosphorylated and total), which normally increase during expression of LTP, are elevated in ganglia isolated from aged rats compared to those from adult ones. Protein levels of calcineurin, which dephosphorylates P-CaMKII, were reduced in ganglia isolated from aged rats, probably as a support mechanism to allow prolonged phosphorylation of CaMKII. Our findings suggest in vivo expression of gLTP in sympathetic ganglia of aged animals, which may contribute to the moderate hypertension often seen in aged subjects.

Expression of gLTP in sympathetic ganglia of obese Zucker rats in vivo: molecular evidence

Long-term potentiation in sympathetic ganglia (gLTP) is similar to LTP of the hippocampal area CA1 in that its expression involves similar changes in signaling molecules. We have shown previously that the stress-prone, hypertensive obese Zucker rats (OZR) expressed gLTP in sympathetic ganglia and that high blood pressure was reduced by treatment with 5-HT(3) receptor antagonists. In the present study, we present additional electrophysiological evidence for the pre-expression of gLTP in sympathetic ganglia from OZR indicated by failure of repetitive stimulation to express gLTP in isolated superior cervical ganglia (SCG) and inhibition of baseline ganglionic transmission by a 5-HT(3) receptor antagonist. We have also investigated the role of key signaling molecules in the expression of gLTP in the hypertensive OZR. Immunoblot analysis showed a significant increase in the levels of phosphorylated (P-)CaMKII and protein kinase C gamma (PKCgamma) in SCG from OZR. The ratio of P-CaMKII to the total CaMKII was markedly increased in OZR ganglia, suggesting increased phosphorylation of this molecule. Additionally, there was a significant decrease in the levels of calcineurin in ganglia. Furthermore, the neural nitric oxide synthase and hemeoxygenase II, which are essential for the expression of gLTP, were significantly elevated in OZR ganglia. The present findings confirm that ganglia from OZR have expressed gLTP and that synaptic plasticity in sympathetic ganglia may involve a molecular cascade similar to that of LTP of the brain hippocampal area CA1.

Reversal of cisplatin-induced carnitine deficiency and energy starvation by propionyl-L-carnitine in rat kidney tissues

1. The present study examined whether propionyl-L-carnitine (PLC) could prevent the development of cisplatin (CDDP)-induced acute renal failure in rats. 2. Forty adult male Wistar albino rats were divided into four groups. Rats in the first group were injected daily with normal saline (2.5 mL/kg, i.p.) for 10 consecutive days, whereas the second group received PLC (250 mg/kg, i.p.) for 10 consecutive days. Animals in the third group were injected daily with normal saline for 5 consecutive days before and after a single dose of CDDP (7 mg/kg, i.p.). Rats in the fourth group received a combination of PLC (250 mg/kg, i.p.) for 5 consecutive days before and after a single dose of CDDP (7 mg/kg, i.p.). On Day 6 following CDDP treatment, animals were killed and serum and kidneys were isolated for analysis. 3. Injection of CDDP resulted in a significant increase in serum creatinine, blood urea nitrogen (BUN), thiobarbituric acid-reactive substances (TBARS) and total nitrate/nitrite (NO(x)), as well as a significant decrease in reduced glutathione (GSH), total carnitine, ATP and ATP/ADP in kidney tissues. 4. Administration of PLC significantly attenuated the nephrotoxic effects of CDDP, manifested as normalization of the CDDP-induced increase in serum creatinine, BUN, TBARS and NO(x) and the CDDP-induced decrease in total carnitine, GSH, ATP and ATP/ADP in kidney tissues. 5. Histopathological examination of kidney tissues from CDDP-treated rats showed severe nephrotoxicity, in which 50-75% of glomeruli and renal tubules exhibited massive degenerative changes. Interestingly, administration of PLC to CDDP-treated rats resulted in a significant improvement in glomeruli and renal tubules, in which less than 25% of glomeruli and renal tubules exhibited focal necrosis. 6. Data from the present study suggest that PLC prevents the development of CDDP-induced acute renal injury by a mechanism related, at least in part, to the ability of PLC to increase intracellular carnitine content, with a consequent improvement in mitochondrial oxidative phosphorylation and energy production, as well as its ability to decrease oxidative stress. This will open new perspectives for the use of PLC in the treatment of renal diseases associated with or secondary to carnitine deficiency.

Carnitine esters prevent oxidative stress damage and energy depletion following transient forebrain ischaemia in the rat hippocampus

1. The present study investigated whether propionyl-L-carnitine (PLC) has neuroprotective effects, similar to those reported for acetyl-L-carnitine (AC), against transient forebrain ischaemia-induced neuronal damage and biochemical derangement in the rat hippocampal CA1 region. 2. In total, 105 adult male Wistar albino rats were divided into seven groups of 15 animals each. The first three groups were injected i.p. with normal saline, AC (300 mg/kg) or PLC (300 mg/kg) for 7 successive days. The next three groups were injected i.p. with the same doses of normal saline, AC or PLC immediately after the induction of 10 min forebrain ischaemia and i.p. injections were continued for 7 successive days. Rats in the seventh group were subjected to sham-operated ischaemia and injected with normal saline for 7 successive days. 3. Seven days after treatment, animals were killed and their brains isolated for histopathological examination and biochemical studies. 4. Forebrain ischaemia resulted in a significant decrease in the number of intact neurons (77%), ATP concentration (51%) and glutathione content (32%), whereas there was a significant increase in the production of thiobarbituric acid-reactive substances (TBARS; 71%) and total nitrate/nitrite (NOx; 260%) in hippocampal tissues. 5. Administration of either AC or PLC attenuated forebrain ischaemia-induced neuronal damage, manifested by a greater number of intact neurons, ATP and glutathione, as well as a decrease in TBARS and NOx in hippocampal tissues. 6. Results from the present study suggest, for the first time, that PLC attenuates forebrain ischaemia-induced neuronal injury, oxidative stress and energy depletion in the hippocampal CA1 region. Propionyl-L-carnitine has neuroprotective effects similar to AC and could have a potential use in the treatment of neurodegenerative diseases. 7. The results of the present study will open up new perspectives for the use of PLC in the treatment of neurodegenerative diseases associated with, or secondary to, myocardial ischaemia-reperfusion injury and chronic circulatory failure.

Effect of metformin on clastogenic and biochemical changes induced by adriamycin in Swiss albino mice

Diabetes mellitus (DM) is a chronic disease that is characterized by deteriorating glycemic control. The disease is known to be caused by imbalance between reactive oxygen species (ROS) and antioxidant defense systems. Hyperglycemia is commonly observed in a wide variety of diseases, including cancer. Although, therapy against glycemic control, is used in all these diseases, the diabetic cancer patients are on additional therapy with anticancer drugs. The objective of present study was to study if Glucophage (metformin), a very popular antidiabetic agent can avert the mutagenicity and lipid peroxidation caused by adriamycin (ADR), which is a commonly used cytotoxic drug. The experimental protocol included oral treatment of mice with different doses (62.5, 125 and 250 mg/kg day) of metformin for 7 days. Some mice in each group were injected i.p. with ADR (15 mg/kg). In each case animals were killed, 30 or 24, 48 and 72 h after the last treatment and femurs were excised for cytological studies by micronucleus test. Additional experiments on estimation of glutathione (GSH) and malondialdehyde (MDA) were undertaken in blood and serum, respectively. Twenty-four hour after the treatment, blood from each mouse was collected from heart and preserved for analysis. The results obtained revealed that pretreatment with metformin: (i) reduced the ADR-induced frequency of micronuclei without any alteration in its cytotoxicity and (ii) protected against the ADR-induced increase and decrease of MDA and GSH, respectively. The exact mechanism of action is not known, however, the inhibition of ADR-induced clastogenicity and lipid peroxidation by metformin may be attributed to the antioxidant action of the latter. Our results demonstrate that metformin might be useful to avert secondary tumor risk by decreasing the accumulation of free radicals and inhibition of mutagenicity.

Postjunctional synergism of norepinephrine with ATP and diadenosine tetraphosphate in Guinea pig vas deferens. Role of protein kinase C and Myosin light chain phosphatase

In isolated guinea pig vas deferens, prior addition of norepinephrine (NE) significantly potentiated the contractile responses to adenosine-5'-triphosphate (ATP) and diadenosine tetraphosphate (AP4A) in a dose-dependent manner up to 240% of the control purine dose. The myosin light chain phosphatase (MLCP) inhibitor cantharidin at a dose of 10 micromol/l caused significant enhancement of ATP at concentrations of 1 and 3 mmol/l by 91 and 95% respectively. Similarly, cantharidin enhanced the contraction to AP4A, 30 and 100 micromol/l by 92 and 100% respectively. Inhibition of protein kinase C (PKC) by the use of chelerythrine (10 micromol/l), incubated at the vas deferens for 60 min, inhibited the NE-induced enhancement of purine-induced contraction. Chelerythrine reversed the NE-ATP and NE-AP4A synergism back close to control ATP and AP4A contraction values respectively. It can be concluded that postjunctional synergism becomes evident not only for adenine mononucleotides and NE but also for diadenosine polyphosphates presented here by AP4A in the guinea pig vas deferens. This synergism involves receptor-mediated activation of PKC and possibly PKC-induced inhibition of MLCP.

Adult-onset hypothyroidism facilitates and enhances LTD: Reversal by chronic nicotine treatment

Chronic nicotine treatment reverses hypothyroidism-induced impairment of hippocampus-dependent spatial memory and long-term potentiation (LTP). We investigated the effect of hypothyroidism on long-term depression (LTD) and possible protection by nicotine. Following paired pulse stimulation, LTD was expressed in hippocampal area CA1 of anesthetized thyroidectomized, euthyroid (sham control), nicotine-treated and nicotine-treated thyroidectomized (hypothyroid) rats. In hypothyroid rats, a significantly higher LTD magnitude was seen compared with that in control rats. A brief train of stimuli (5 pulses at 100 Hz), which did not affect synaptic transmission in control rats, induced a robust LTD in hypothyroid rats suggesting facilitation of LTD expression in these rats. Chronic nicotine treatment (1 mg/kg, 2x day) of hypothyroid rats reversed hypothyroidism-induced enhancement and facilitation of LTD. Western blot analysis of the NMDA receptor subunits in the membranous fractions of hippocampal area CA1 neurons revealed that hypothyroidism reduced NR1 and increased NR2B without affecting NR2A protein levels. These changes in NMDA receptors in hypothyroid rats were reversed by chronic nicotine treatment. Hypothyroidism did not alter BDNF or nicotinic acetylcholine receptor (nAChR) levels. However, nicotine treatment increased protein levels of these molecules in both euthyroid and hypothyroid rats. Our results suggest that alterations in the levels of NMDA receptor subunits may account for the facilitation and enhancement of LTD in hypothyroidism.

Nicotine prevents disruption of the late phase LTP-related molecular cascade in adult-onset hypothyroidism

We have shown previously that chronic nicotine treatment reverses adult-onset hypothyroidism-induced impairment of late-phase long-term potentiation (L-LTP) in area CA1 of the hippocampus. In the present study, basal and stimulated levels of signaling molecules essential for the expression of L-LTP were determined in area CA1. Immunoblots analysis showed that chronic nicotine treatment of hypothyroid rats prevented the reduction in the basal protein levels of adenylyl cyclase I (ACI), mitogen-activated protein kinases [MAPKp44/42 (ERK1/2)], calcium-calmodulin-dependent protein kinase IV (CaMKIV), and cyclic-AMP response element binding protein [CREB; phosphorylated (P-) and total]. A significant increase in the levels of P-CREB, P-MAPKp44, P-MAPKp42 and brain derived neurotrophic factor (BDNF) was seen 4 h after multiple train high frequency stimulation (MHFS) in nicotine-treated hypothyroid and control animals, but not in hypothyroid animals. The levels of total CREB, total MAPKp44, total MAPKp42, and CaMKIV were elevated in all groups 4 h after MHFS. These findings suggest that prevention of the reduced basal level of CaMKIV, MAPKp44/42, and CREB by nicotine along with the regained ability of MHFS to induce MAPKp44/42 and CREB phosphorylation in nicotine treated hypothyroid animals may be responsible for the reversal of L-LTP impairment by chronic nicotine treatment in this disease model.

Molecular studies on the protective effect of nicotine in adult-onset hypothyroidism-induced impairment of long-term potentiation

We have recently shown that chronic nicotine treatment reverses hypothyroidism-induced learning and memory impairment. Chronic nicotine treatment also reverses the hypothyroidism-induced impairment of long-term potentiation (LTP). Analysis of LTP associated key signaling molecules revealed that chronic nicotine treatment prevented the hypothyroidism-induced reduction of the basal phosphotransferase activity of CaMKII and protein levels of P-CaMKII. In addition, the failure of high frequency stimulation to increase the levels of P-CaMKII in hypothyroid rats was reversed by nicotine treatment, suggesting that the neuroprotective effect of nicotine during hypothyroidism involved activation of CaMKII. Furthermore, chronic nicotine treatment reverses the hypothyroidism-induced elevated phosphatase activity and protein levels of calcineurin, a phosphatase that regulates CaMKII activation. We conclude that the neuroprotective effects of nicotine in adult-onset hypothyroidism may result from restoration of CaMKII and calcineurin activity.

Nicotine reverses adult-onset hypothyroidism-induced impairment of learning and memory: Behavioral and electrophysiological studies

Nicotine alleviates cognitive impairment associated with a variety of health conditions. We examined the effect of chronic nicotine treatment on adult-onset hypothyroidism-induced impairment of learning and memory in rats. Hypothyroidism was induced by surgical removal of thyroid glands (thyroidectomy). One month later, chronic nicotine treatment (1 mg/kg sc, twice/day) was instituted for 4-6 weeks. Test of hippocampus-dependent spatial learning and memory in the radial arm water maze showed that hypothyroidism impaired learning as well as short-term and long-term memory retention. Chronic nicotine treatment reversed the hypothyroidism-induced learning and memory impairment. In normal rats, chronic nicotine treatment had no effect on learning and memory. Extracellular recordings from the CA1 region of anesthetized hypothyroid rats showed severe reduction of both early-phase and late-phase long-term potentiation (LTP) magnitude, which was reversed in nicotine-treated hypothyroid rats. These results show that chronic nicotine treatment prevents hypothyroidism-induced impairment of spatial cognition and LTP.

Nicotine blocks stress-induced impairment of spatial memory and long-term potentiation of the hippocampal CA1 region

The effect of chronic nicotine treatment on chronic psychosocial stress-induced impairment of short-term memory and long-term potentiation (LTP) was determined. An "intruder" stress model was used to induce psychosocial stress for 4-6 wk, during which rats were injected with saline or nicotine (1 mg/kg s.c.) twice a day. The radial arm water maze memory task was used to test hippocampus-dependent spatial memory. Chronic psychosocial stress impaired short-term memory without affecting the learning phase or long-term memory. Concurrent chronic nicotine treatment prevented stress-induced short-term memory impairment. In normal rats chronic nicotine treatment had no effect on learning and memory. Extracellular recordings from the CA1 region of anaesthetized rats showed severe reduction of LTP magnitude in stressed rats, which was normalized in nicotine-treated stressed rats. Nicotine had no effect on LTP in control animals. These results showed that chronic nicotine treatment improved hippocampus-dependent spatial memory and LTP only when impaired by stress.

Chronic but not acute nicotine treatment reverses stress-induced impairment of LTP in anesthetized rats

Stress impairs long-term potentiation (LTP) and is a major cause for starting or increasing tobacco smoking. We have previously shown that chronic concurrent nicotine treatment prevents stress-induced LTP impairment. Nicotine reduces stress-induced impairment of LTP, probably, through activation of nicotinic acetylcholine receptors in the hippocampus. Herein, we investigated the effects of acute and chronic nicotine treatments on the chronic-stress-induced impairment of LTP in area CA1 of the hippocampus of urethane-anesthetized rats. Extracellular in vivo recording from the hippocampal area CA1 showed that pre-treatment with nicotine (1 mg/kg; sc twice/day for 2 weeks prior to stress) protected LTP from the inhibitory effect of subsequent chronic psychosocial stress (4 additional weeks concurrently with nicotine). In another series of experiments, 2 weeks of psychosocial stress was followed by 4 weeks of nicotine treatment concurrently with continuing stress. Nicotine treatment reversed established stress-induced impairment of LTP. However, acute nicotine treatment of rats (a single dose of 1 mg/kg; sc.) did not reverse chronic-stress-induced impairment of LTP. The results show that the impairment of LTP during chronic stress can be blocked by chronic, but not acute, nicotine treatment.

Nicotine prevents stress-induced enhancement of long-term depression in hippocampal area CA1: electrophysiological and molecular studies

Nicotine treatment prevents chronic psychosocial stress-induced impairment of hippocampus-dependent spatial memory and long-term potentiation (LTP). In this study, we investigated the effect of chronic nicotine treatment on stress-induced enhancement of long-term depression (LTD). After paired-pulse stimulation, LTD was evoked in area CA1 of anesthetized control, stressed, nicotine-treated, and nicotine-treated stressed rats. In stressed rats, a significantly greater LTD magnitude was seen than in control rats. Stress also facilitated the induction of LTD. Nicotine treatment of stressed rats prevented stress-induced enhancement and facilitation of LTD. For chronically stressed rats, we previously reported marked decreases in the basal levels of brain-derived neurotrophic factor (BDNF), CaMKII, P-CaMKII, and calmodulin as well as a significant increase in calcineurin basal levels. Herein, Western blot analysis conducted 1 hr after induction of LTD by paired-pulse stimulation showed that the levels of calcineurin and P-CaMKII were increased in the stressed group compared with the other groups and were normalized by chronic nicotine treatment. Additionally, after paired-pulse stimulation, the levels of total CaMKII were increased in all groups with no change in the levels of BDNF and calmodulin. Therefore, the increase in the levels of calcineurin and P-CaMKII during expression of LTD in area CA1 may explain the enhanced magnitude of LTD in chronically stressed rats.

Chronic psychosocial stress-induced impairment of hippocampal LTP: possible role of BDNF

Electrophysiological recording reveals that chronic nicotine treatment prevents stress-induced impairment of long-term potentiation (LTP) in the CA1 region of the hippocampus of anesthetized rats. We investigated the molecular mechanism of this action of nicotine in the CA1 region. Immunoblot analysis showed that chronic nicotine treatment (1 mg/kg, 2 times/day) normalized the stress-induced decrease in the basal levels of BDNF, CaMKII (total and phosphorylated; P-CaMKII), and calmodulin. Additionally, nicotine reversed the stress-induced increase in calcineurin basal levels. Chronic nicotine treatment also markedly increased the basal levels of BDNF in naïve rats. Furthermore, high-frequency stimulation (HFS), which increased the levels of P-CaMKII in control as well as nicotine-treated stressed rats, failed to increase P-CaMKII levels in untreated stressed rats. Compared to unstimulated control, the levels of both total CaMKII and calcineurin were increased after HFS in all groups including the stressed, but no changes were detected after HFS in the levels of BDNF and calmodulin. These results indicate that normalization by nicotine of the stress-induced changes in the levels of signaling molecules including BDNF may contribute to the recovery of LTP.

Impairment of long-term potentiation in the CA1, but not dentate gyrus, of the hippocampus in Obese Zucker rats: role of calcineurin and phosphorylated CaMKII

Obese Zucker rat (OZR) is a genetic model of obesity with noninsulin-dependent diabetes and hypertension. The OZR exhibit hyperinsulinemia, hyperlipidmia, and high circulating glucocorticoid levels. We have shown previously that long-term potentiation (LTP) is impaired in the CA1 region of the hippocampus of OZR. In the present work, although electrophysiological recording from anesthetized OZR hippocampus showed impaired LTP in the CA1, an intact LTP was recorded in the dentate gyrus (DG) region of the hippocampus of the same OZR. Thus, LTP is differentially impaired in the CA1 compared with the DG region of OZR hippocampus. Immunoblotting was used to investigate the molecular mechanism responsible for impairment of LTP in the CA1 but not in the DG region. Analysis revealed reduction in the levels of phosphorylated calcium-dependent calmodulin kinase II (P-CaMKII) and total CaMKII in the CA1 region of OZR. However, in the DG region, reduction was observed only in the levels of total CaMKII, with no change in P-CaMKII levels. The ratio of P-CaMKII to total CaMKII was increased in the DG but not in the CA1 area of hippocampus of OZR. Although unchanged in the CA1, calcineurin levels were significantly reduced in the DG of OZR. These findings suggest that the DG might possess a compensatory mechanism whereby calcineurin levels are reduced to allow sufficient P-CaMKII to produce an apparently normal LTP in the DG area of OZR hippocampus.

Propionyl-L-carnitine prevents the progression of cisplatin-induced cardiomyopathy in a carnitine-depleted rat model

This study has been initiated to investigate whether endogenous carnitine depletion and/or carnitine deficiency is a risk factor during development of cisplatin (CDDP)-induced cardiomyopathy and if so, whether carnitine supplementation by propionyl-L-carnitine (PLC) could offer protection against this toxicity. To achieve the ultimate goal of this study, a total of 60 adult male Wistar albino rats were divided into six groups. The first three groups were injected intraperitoneally with normal saline, PLC (500 mg kg(-1)), and d-carnitine (500 mg kg(-1)) respectively, for 10 successive days. The 4th, 5th, and 6th groups were injected intraperitoneally with the same doses of normal saline, PLC and D-carnitine, respectively, for 5 successive days before and after a single dose of CDDP (7 mg kg(-1)). On day 6 after CDDP treatment, animals were sacrificed, serum as well as hearts were isolated and analyzed. CDDP resulted in a significant increase in serum creatine phosphokinase isoenzyme (CK-MB) and lactate dehydrogenase (LDH), thiobarbituric acid reactive substances (TBARS) and total nitrate/nitrite (NO(x)) and a significant decrease in reduced glutathione (GSH), total carnitine, and adenosine triphosphate (ATP) content in cardiac tissues. In the carnitine-depleted rat model, CDDP induced dramatic increase in serum cardiomyopathy enzymatic indices, CK-MB and LDH, as well as progressive reduction in total carnitine and ATP content in cardiac tissue. Interestingly, PLC supplementation resulted in a complete reversal of the increase in cardiac enzymes, TBARS and NO(x), and the decrease in total carnitine, GSH and ATP, induced by CDDP, to the control values. Moreover, histopathological examination of cardiac tissues confirmed the biochemical data, where PLC prevents CDDP-induced cardiac degenerative changes while d-carnitine aggravated CDDP-induced cardiac tissue damage. In conclusion, data from this study suggest for the first time that carnitine deficiency and oxidative stress are risk factors and should be viewed as mechanisms during development of CDDP-related cardiomyopathy and that carnitine supplementation, using PLC, prevents the progression of CDDP-induced cardiotoxicity.

Psychosocial stress-induced hypertension results from in vivo expression of long-term potentiation in rat sympathetic ganglia

Long-term potentiation in sympathetic ganglia (gLTP) is an activity-dependent unique form of synaptic plasticity in that it is serotonin-dependent and can be completely inhibited by 5-HT3 receptor antagonists. Long lasting enhancement of the basal tone of ganglionic transmission seen with gLTP results in a sustained increase in peripheral resistance that leads to elevated blood pressure. We examined the possibility that, in sympathetic ganglia, stress-induced gLTP may be responsible for the expression of stress hypertension. Chronic treatment of male and female Wistar rats with a 5-HT3 receptor antagonist, tropisetron (ICS; 5 mg/kg/day) or ondansetron (0.5 mg/kg/day), prevented or reversed psychosocial stress-induced increases in blood pressure in stressed rats with no significant effect on blood pressure of unstressed control rats. Pharmacological and electrophysiological evidence that supports the presence of gLTP in ganglia isolated from stressed hypertensive rats includes inhibition of basal synaptic transmission by 5-HT3 antagonists, failure to induce gLTP with repetitive stimulation indicating occlusion of gLTP due to saturation and a left hand shift of the input/output curve. We suggest that a sustained stress-induced increase in central sympathetic efferent impulses to ganglia may provide the repeated high frequency presynaptic activity required to induce gLTP in sympathetic ganglia, thereby enhancing sympathetic tone to blood vessels resulting in hypertension.

Plasticity of synaptic transmission in autonomic ganglia

Synaptic plasticity is a term that describes long-lasting changes in the efficacy of synaptic transmission resulting from certain patterned activities of the presynaptic nerve. One form of synaptic plasticity, long-term potentiation (LTP), is an activity-dependent marked increase in synaptic efficacy that has been extensively studied in various regions of the central nervous system, particularly the hippocampus, where LTP is widely believed to be a cellular correlate of learning and memory. A similar phenomenon has been identified in sympathetic ganglia even before Bliss and Lomo coined the term LTP in 1973. Ganglionic LTP (gLTP) of the nicotinic pathway is a similarly long-lasting increase in synaptic effectiveness that can be induced in ganglia following a brief train of relatively high frequency stimulation (HFS) of the preganglionic nerve. Remarkably similar to the LTP of the hippocampus, gLTP has been demonstrated in autonomic ganglia from a number of vertebrates including mammalian, amphibian and avian species. Several other forms of long-lasting increases in synaptic effectiveness have been demonstrated in sympathetic ganglia following exposure to adrenergic agonists, neuroactive peptides and cyclic nucleotides and even after a challenge by an antigen. The main emphasis of this review, however, will be on the activity-dependent gLTP of the mammalian sympathetic ganglia, in particular the superior cervical ganglion of the rat. Since the last, excellent and comprehensive review of this ganglionic function by Briggs in 1995, important discoveries about the mechanisms of induction and maintenance of gLTP have been reported, including the finding that the response is uniquely dependent on serotonin for both the induction phase and maintenance phase. These new advances will be discussed in depth in this review.

Hypothyroidism impairs long-term potentiation in sympathetic ganglia: electrophysiologic and molecular studies

Electrophysiologic and molecular techniques were used to study the effect of adult-onset hypothyroidism on synaptic plasticity in the superior cervical sympathetic ganglion. Ganglia excised from adult thyroidectomized and sham-operated rats were subjected to a brief high-frequency stimulation of the preganglionic nerve to express long-term potentiation (gLTP). Western blotting was carried out to determine the protein levels of key signaling molecules that may be involved in the expression of gLTP. Input/output relationship in ganglia from hypothyroid rats indicated a normal basal synaptic transmission, whereas activity-dependent types of synaptic plasticity, posttetanic potentiation (PTP) and gLTP, were impaired. Immunoblot analysis showed that both calcium/calmodulin kinase II (CaMKII) and phosphorylated CaMKII (P-CaMKII) levels were reduced markedly in hypothyroid rat ganglia compared to those from euthyroid controls. Additionally, protein levels of nitric oxide synthase-1, heme oxygenase-2, calmodulin, protein kinase C (PKC), and calcineurin were also reduced in hypothyroid rat ganglia. The results indicate that abnormally low basal levels of signaling molecules may be responsible for hypothyroidism-induced impairment of gLTP in superior cervical ganglia. In addition, the results indicate that synaptic plasticity in sympathetic ganglia may involve a molecular sequence of events similar to that proposed for LTP in the hippocampus.

Reduced basal CAMKII levels in hippocampal CA1 region: Possible cause of stress-induced impairment of LTP in chronically stressed rats

Chronic psychosocial stress markedly reduces the expression of high-frequency stimulation (HFS)-evoked early long-term potentiation (LTP) in the CA1 region of the hippocampus of anesthetized rats. Immunoblotting was performed to determine changes in molecular levels of key signaling proteins that might be responsible for this inhibitory effect. Western blot analysis of the CA1 region demonstrates that chronic psychosocial stress decreases basal levels of calcium calmodulin kinase II (CaMKII), phosphorylated (P)-CaMKII, calmodulin, and protein kinase C (PKCgamma) while markedly increasing protein phosphatase 2B (calcineurin) levels. The decrease of basal levels of P-CaMKII may be triggered primarily by excessive dephosphorylation resulting from enhanced basal levels of calcineurin. The decline in the basal levels of the upstream molecules, PKCgamma and calmodulin may be a consequence of the diminished basal P-CaMKII levels. Analysis of signaling molecules in CA1 region of chronically stressed rat subjected to HFS in vivo showed only one difference compared to similarly stimulated control rats; no increase in P-CaMKII levels. Our results suggest that decreased P-CaMKII levels may be primarily responsible for the stress-induced reduction in LTP expression.

Impaired long-term potentiation in obese zucker rats: possible involvement of presynaptic mechanism

Electrophysiological investigation of basal synaptic transmission and synaptic plasticity in the CA1 region of the hippocampus was carried out in anesthetized obese Zucker rats (OZR). Comparison of the input/output curves of basal field excitatory postsynaptic potential indicates that these are similar in both the OZR and its lean counterpart suggesting that basal synaptic transmission is intact in the OZR. However, high frequency stimulation evokes long-term potentiation (LTP) in the lean rat but not in the OZR. Since post-tetanic potentiation and paired pulse facilitation, forms of short-term potentiation of presynaptic origin, are also severely impaired in the OZR, the results imply that impairment of CA1 hippocampal LTP in these obese rats may be due, in part, to impaired presynaptic function. The results emphasize the potential deleterious effect of obesity on learning and memory functions of the CNS.

Chronic psychosocial stress decreases calcineurin in the dentate gyrus: a possible mechanism for preservation of early ltp

Chronic psychosocial stress impairs early long-term potentiation (LTP) in the hippocampal CA1 region but not in the dentate gyrus of anesthetized rats. Analysis of putative signaling molecules involved in the expression of LTP was performed to determine the possible reason(s) for the apparent resistance of the LTP of the dentate gyrus to chronic psychosocial stress. Immunoblotting was used to determine possible changes in the basal levels of various fractions of calcium-dependent calmodulin kinase II (CaMKII), phosphorylated CaMKII (P-CaMKII), calmodulin, protein kinase C gamma (PKCgamma) and calcineurin in the dentate gyrus of chronically stressed rats. Western blot analysis revealed that chronic stress significantly decreased the levels of the total CaMKII without affecting P-CaMKII levels. No significant change was detected in the levels of the upstream effectors, calmodulin and PKCgamma. However, chronic stress produced a significant decrease in calcineurin levels. The data suggest that the dentate gyrus of chronically stressed rats may have developed a compensatory mechanism whereby calcineurin levels are reduced to maintain normal P-CaMKII levels, which may be responsible for the normal early LTP of the dentate gyrus of chronically stressed rats. The results of this work will increase understanding of why certain brain regions are more resistant to deleterious effects of conditions that deteriorate learning and memory.

Reduction of elevated arterial blood pressure in obese Zucker rats by inhibition of ganglionic long-term potentiation

Sustained enhancement of the basal tone of ganglionic transmission is expected to result in an enduring increase in peripheral resistance that would lead to elevated blood pressure. Long-term potentiation of sympathetic ganglia is an activity-dependent long-lasting increase in strength of ganglionic transmission. Therefore, ganglionic long-term potentiation might be involved in the manifestation of neurogenic forms of hypertension. Expression of sympathetic ganglionic long-term potentiation is dependent on activation of 5-HT(3) receptor. We examined the possibility that elevated blood pressure in obese Zucker rat, which is reported to be stress-prone, might be partly due to a neurogenic factor resulting from expression of ganglionic long-term potentiation. Chronic treatment with the 5-HT(3) receptor antagonist ondansetron (0.5 mg/kg/day) caused a significant decrease in blood pressure of the obese Zucker rats without affecting that of normotensive lean Zucker rats. Electropysiological procedures to test for long-term potentiation in isolated ganglia suggest that ganglionic long-term potentiation has been previously expressed in vivo in ganglia from obese Zucker rat but not in those from the normotensive lean Zucker rats. The results indicate that expression of ganglionic long-term potentiation in sympathetic ganglia may be responsible for neurogenic increase in blood pressure, which contributes to the moderate hypertension often seen in the obese Zucker rats.