Prevalence of proteinuria and its associated factors in hypertensive diabetic patients

OBJECTIVE

Hypertensive diabetic patients are at increased risk for chronic kidney disease. Proteinuria is an early sign of kidney damage. Limited research is available on proteinuria and on its associated factors in hypertensive patients with diabetes. This study aimed to assess the prevalence of proteinuria and its associated factors in hypertensive diabetic patients.

PATIENTS AND METHODS

The current retrospective study utilized medical records and hospital computers to collect sociodemographic and medical information about the study patients in two major hospitals in Jordan. Binary regression analysis was used to find the factors that are significantly and independently associated with the presence of proteinuria.

RESULTS

Data from 522 hypertensive diabetic patients were investigated. Factors including age (OR=0.691; 95% CI: 0.930-0.994; p<0.01), high-density lipoprotein level (OR=0.450; 95% CI: 0.211-0.960; p<0.05), and higher glomerular filtration rate (OR=0.964; 95% CI: 0.950-0.977; p<0.01) were associated with proteinuria among the study patients. In contrast to metformin (OR=0.237; 95% CI: 0.098-0.572; p<0.01), patients who received insulin (OR=1.992; 95% CI: 1.136-3.492; p<0.05), thiazide diuretics (OR=1.848; 95% CI: 1.108-3.083; p<0.05), calcium channel blockers (OR=1.833, 95% CI: 1.110-3.028, p<0.05), or beta-blockers (BBs) (OR=2.199, 95% CI: 1.257-3.848, p<0.01) had a higher likelihood of having proteinuria.

CONCLUSIONS

For preserving kidney function, it is deemed necessary to perform regular checkups for proteinuria among hypertensive diabetic patients, particularly in young patients, patients with low levels of high-density lipoprotein, and those with a lower glomerular filtration rate.

Comparison of Effects of Spatial and Non-Spatial Memory Acquisition on the CaMKII Pathway During Hypothyroidism and Nicotine Treatment

Molecular, cellular, and behavioral studies have shown that hypothyroidism impairs hippocampus-dependent learning and memory in adult rats. In these studies, spatial learning and memory were tested in the radial arm water maze (RAWM), which involved locating a hidden platform. In the present study, we investigated the effects of nicotine and hypothyroidism on the CaMKII pathway during learning and memory processes in both spatial and non-spatial memory forms. We used nicotine as a neuroprotective agent. Hypothyroidism was induced by thyroidectomy in adult rats. Rats were trained on the hidden platform (the RAWM for spatial learning and memory) and compared with age-matched rats that were trained on a clearly visible platform system (2 cm above water with no radial arms for non-spatial learning and memory). Nicotine (1 mg/kg twice/day) was administered subcutaneously for 4 weeks. Immediately after training, the protein levels of memory-related signaling molecules were determined in hippocampal area CA1. Western blot analysis revealed a significant increase in calcineurin levels and decreases in P-CaMKII, PKCγ, and calmodulin protein levels in area CA1 of the hippocampi of hypothyroid rats trained on both the visible and hidden platforms. Nicotine treatment normalizes these levels in hypothyroid rats trained on both the visible and hidden platforms. The results suggest that chronic nicotine treatment prevents hypothyroidism-induced suppression of the CaMKII pathway after spatial and non-spatial learning and memory.

The role of fish oil in attenuating cardiac oxidative stress, inflammation and fibrosis in rat model of thyrotoxicosis

Hyperthyroidism is associated with cardiovascular complications. Fish oil reduces risk of cardiovascular diseases. This study aims to evaluate the impact of fish oil on myocardial oxidative stress, inflammation and fibrosis in rat model of thyrotoxicosis. Rats were randomized into four groups; control rats, fish oil treated rats (FO, 100mg omega-3/100g body weight/day), hyperthyroid rats (Hyper, i.p levothyroxine 3 mg/kg/day), and hyperthyroid rats treated with fish oil (Hyper + FO) for 8 weeks. Changes in oxidants/antioxidants, inflammatory and fibrotic markers were measured. Thyrotoxicosis increased serum endothelin-1, thiobarbituric acid reactive substances (TBARS) and reduced activities of cardiac catalase and super oxide dismutase (SOD). Cardiac fibrosis paralleled with a decrease of matrix metalloproteinase -2 (MMP2) levels were observed in Hyper group. Use of FO increased activities of SOD and catalase, increased TBARS levels, and attenuated cardiac fibrosis by normalizing MMP-2 levels. Use of FO may attenuate cardiac oxidative stress and fibrosis in hyperthyroid states.

Cardiac effects of cigarette tobacco smoking in rat model of diabetes

AIMS

Tobacco smoking is considered a global health issue, contributing to increased risk of cardiovascular disease (CVD) and diabetes (DM). We aimed to assess effects of cigarette smoking on cardiac inflammation, oxidative stress and fibrosis in rat model of streptozotocin (STZ)-induced diabetes.

MAIN METHODS

Adults Wistar rats were assigned into control (fresh air, intraperitoneal injection (i.p) of citrate buffer), cigarette smoking (1 h daily for 4 weeks, i.p citrate buffer), DM (35 STZ mg/kg single i.p, fresh air), and DM + Smoking groups for 4 weeks. Cardiac biomarkers of oxidative stress, inflammation, and fibrosis were evaluated.

KEY FINDINGS

STZ-induced diabetes as documented by the persistent increase in blood glucose. Relative to control, a significant decrease in body weight was observed in diabetic groups paralleled with increased heart to body weight ratio and systolic blood pressure in all groups. Levels of total nitrite, thiobarbituric acid substances, endothelin -1, interleukin-6 and myeloperoxidase were increased in the DM, Smoking and DM + Smoking groups without changes in C-reactive protein. Cardiac levels of GSH were increased in Smoking groups whereas activities of catalase and superoxide dismutase increased in DM, Smoking and DM + Smoking groups. DM but not smoking increased cardiac fibrosis with a parallel increase in transforming growth factor beta. Cardiac levels of matrix metalloproteinase-2 were elevated in Smoking groups and decreased in DM.

SIGNIFICANCE

Exposure to cigarette smoke may increase risk of CVD in DM by increased cardiac oxidative stress and inflammation. Smoking was associated with increased oxidant enzymes and metalloproteinase-2 probably to prevent cardiac fibrosis.

Cardiac effects of fish oil in a rat model of streptozotocin-induced diabetes

BACKGROUND AND AIMS

Fish oil (FO) is rich in omega-3 polyunsaturated fatty acids, which have cardio-protective effects. This study aims to evaluate effects of FO in a rat model of streptozotocin (STZ) induced diabetes.

METHODS AND RESULTS

Adults male Wistar rats were assigned to control (4 μl corn oil/g corn oil given by oral gavage), FO (4 μl Menhaden FO/g body weight given by oral gavage), diabetes (DM, 35 mg/kg STZ single intraperitoneal injection, corn oil), and DM + FO groups for 8 weeks. Plasma and cardiac biomarkers of oxidative stress, inflammation, and fibrosis were evaluated. STZ-induced diabetes as indicated by the significant increase in serum levels of glucose and percentage of glycated hemoglobins. FO reduced plasma arachidonic acid (AA) percentage and ratio of AA: docosahexaenoic acid (DHA). Plasma and cardiac levels of total nitrite, endothelin -1 (ET-1), and myeloperoxidase (MPO) increased in the DM group, whereas cardiac activities of catalase and superoxide dismutase (SOD) decreased. FO reduced cardiac nitrite and MPO, and plasma ET-1 levels. FO increased cardiac glutathione, catalase and SOD activities. Levels of thiobarbituric acid substances increased in the FO and DM groups with significant synergism in the DM + FO group. FO prevented cardiac fibrosis associated with DM and decreased cardiac transforming growth factor beta-1and p38 MAP kinases. Cardiac levels of matrix metalloproteinase -2 were significantly elevated in FO and DM + FO groups.

CONCLUSIONS

FO decreased plasma and cardiac oxidative stress, inflammation and myocardial fibrosis. FO could be used in diabetes to reduce risk and burden of CVDs.

Assessment of genotoxicity of vincristine, vinblastine and vinorelbine in human cultured lymphocytes: a comparative study

Vincristine (VCR), vinblastine (VBL) and vinorelbine (VRL) are anticancer agents from the Vinca alkaloid family that have the potential to induce genotoxic effect. The aim of the present study was to compare the genotoxic effect of VCR, VBL and VRL. Levels of 8-hydroxy-2-deoxy guanosine (8-OHdG) and sister chromatid exchanges (SCEs) were measured in cultured human blood lymphocytes treated with VCR, VBL and VRL at concentrations of 0.01 and 0.1 μg/mL. Results showed that VCR, VBL and VRL significantly increased the 8-OHdG levels (p <0.05), whereas it did not cause a significant increase in the frequencies of SCEs in human blood lymphocytes as compared to controls. On the other hand, all three agents significantly increased cells mitotic index (p <0.05). At both tested concentrations, the magnitude of the increase in 8-OHdG was VBL>VCR>VRL. In conclusion, VCR, VBL and VRL induce DNA damage as indicated by the increase in the 8-OHdG biomarker but with different magnitude.

Assessment of genotoxicity of waterpipe smoking using 8-OHdG biomarker

Waterpipe tobacco smoking is increasing in popularity, particularly among young adults. This popularity is related to the lack knowledge regarding the health effects of waterpipe smoking. In this study, we examined the genotoxicity of waterpipe smoking using an 8-hydroxy deoxyguanosine (8-OHdG) assay. Genotoxicity was evaluated in the saliva, urine, and serum of 66 waterpipe adult smokers and 46 healthy nonsmokers. The level of addiction to waterpipe smoking was evaluated using the Lebanon Waterpipe Dependence Scale-11. Levels of 8-OHdG in the samples were measured using commercially available enzyme-linked immunosorbent assays. Levels of 8-OHdG in the saliva (52,430 ± 2923 vs 48,430 ± 4189 pg/mL), urine (2815 ± 312 vs 2608 ± 180 pg/mL), and serum (19,720 ± 202 vs 19,670 ± 254 pg/mL) were similar between waterpipe smokers and nonsmokers (P > 0.05). In addition, no correlations were found between dependence score and levels of 8-OHdG in all sample types. In conclusion, 8-OHdG is not a good biomarker for genotoxic effect of waterpipe smoking.

The role of TNF-α G-308A promoter polymorphism in glycemic control in Type 2 diabetes patients

BACKGROUND

TNF-α polymorphisms were shown to be associated with insulin resistance and diabetes development and complications.

AIM

To investigate the association between glycemic control in Type 2 diabetes patients and TNF-α G-308A single nucleotide polymorphism (SNP).

METHODS

This was a cross-sectional observational study, where diabetes patients from both genders (170 male and 185 female) were enrolled in the study. Patients were divided into two groups: good glycemic control (n = 158) and poor glycemic control (n = 197). Genotyping of TNF-α G-308A SNP was carried out using restriction fragment length polymorphisms-polymerase chain reaction.

RESULTS

The results showed that TNF-α G-308A SNP is strongly associated with glycemic control in type 2 diabetes patients. Patients with the AA and AG genotypes had better glycemic control than those with GG genotype (P < 0.01). Other parameters that impacted glycemic control include duration of the disease (P < 0.01) and response to insulin therapy (P < 0.01). However, no contribution for gender or statins use to glycemic control was observed (P > 0.05).

CONCLUSION

TNF-α G-308A SNP might modulate glycemic control among type 2 diabetes patients.

Levothyroxin replacement therapy restores hypothyroidism induced impairment of L-LTP induction: critical role of CREB

Cyclic-AMP response element binding protein (CREB) is a transcription factor crucial for late phase long-term potentiation (L-LTP) induction and maintenance. Upon multiple high frequency stimulation (MHFS), large Ca(2+) influx activates adenylyl cyclase. This, in turn, activates PKA, which by itself or through MAPK p42/p44 can activate (phosphorylate) CREB. Upon phosphorylation, P-CREB activates multiple genes essential for L-LTP generation. Calcium calmodulin kinase IV (CaMKIV) is also activated by calcium and can directly activate CREB. We have shown previously that hypothyroidism impairs L-LTP and reduces the basal protein levels of CREB, MAPK p42/p44, and CaMKIV in area CA1 of the hippocampus. In the present study, levels of these signaling molecules were determined in area CA1 during the induction and maintenance phases of L-LTP. Standard MHFS was used to evoke L-LTP in the CA1 area of hypothyroid, levothyroxin treated hypothyroid and sham control anesthetized adult rats. Chronic levothyroxin treatment reversed hypothyroidism-induced L-LTP impairment. Five minutes after MHFS, western blotting showed an increase in the levels of P-CREB, and P-MAPK p42/p44 in sham-operated control, and levothyroxin treated hypothyroid animals, but not in hypothyroid animals. The protein levels of total CREB, total MAPK p42/p44, BDNF and CaMKIV were not altered in all groups five minutes after MHFS. Four hours after MHFS, the levels of P-CREB, and P-MAPK p42/p44 remained unchanged in hypothyroid animals, while they were elevated in sham-operated control, and levothyroxin treated hypothyroid animals. We conclude that respective normalized phosphorylation of essential kinases such as P-CREB and P-MAPK p42/p44 is correlated with restoration of normal L-LTP induction and maintenance in the CA1 area of levothyroxin-treated hypothyroid animals.

The role of type II deiodinase polymorphisms in clinical management of hypothyroid patients treated with levothyroxine

STUDY OBJECTIVE

Several factors can affect achieving the goals with levothyroxine (L-T4) therapy. This study investigates the clinical and biochemical response to L-T4 replacement therapy in hypothyroid patients in correlation with genetic variation in Deiodinase type || (DIO2) gene.

DESIGN AND SETTING

This is a cross-sectional correlation study. The setting was the diabetes and endocrinology clinics at 2 Jordanian Hospitals.

METHODOLOGY

Patients with primary hypothyroidism who are controlled on stable L-T4 replacement therapy were recruited and thyroid function test was performed. Genetic analysis to detect 4 single nucleotide polymorphisms (SNPs) rs225011, rs7140952, rs225012 and rs2839858 in DIO2 gene was carried out using the polymerase chain reaction-based restriction fragment length polymorphism assay (PCR-RFLP).

RESULTS

There was no correlation between the 4 SNPs in DIO2 gene and replacement doses of L-T4, whereas a statistical significance was found between rs7140952 and central obesity (P<0.05), and systolic and diastolic blood pressure (P<0.05). The dose of L-T4 was associated with lower levels of TSH, fT4, central obesity, body mass index and waist circumference.

CONCLUSION

While L-T4 dose is associated with several positive effects on hypothyroid patients, none of the examined SNPs in DIO2 is correlated with replacement doses of the drug. However, rs7140952 polymorphism is associated with components of metabolic syndrome including blood pressure and central obesity.

Frequency of MDR1 single nucleotide polymorphisms in a Jordanian population, including a novel variant

The multidrug resistance gene (MDR1 or ABCB1) codes for P-glycoprotein, which plays an important role in regulating absorption, distribution, and elimination of drugs. We examined MDR1 gene variants in 100 unrelated subjects from various regions of Jordan. The MDR1 gene was scanned using direct sequencing. Six rare variants in MDR1 were detected, including a new variant, T3075A. This variant did not affect the protein sequence (synonym for threonine). Among the common SNPs, the frequencies of rs1128503 (C1236T) genotypes were: 0.23 (CC), 0.41 (CT) and 0.36 (TT). For the rs2032582 (G2677T) SNP, genotype frequencies were 0.38 for GG, 0.45 for GT, 0.13 for TT, 0.03 for GA, and 0.01 for TA, whereas for rs1045642 (C3435T), genotype frequencies were 0.17 for CC, 0.5 for CT and 0.33 for TT. The observed distribution of the common variants in the Jordanian population was within the range detected in other populations. These data on MDR1 gene variants in the Jordanian population will be useful for investigations on response to P-glycoprotein substrate drugs.

Waterpipe tobacco and cigarette smoking among university students in Jordan

SETTING

While waterpipe and cigarette smoking have been well studied in Syria and Lebanon, data from Jordan are limited.

OBJECTIVES

To characterize the relative prevalence of waterpipe tobacco and cigarette smoking among university students in Jordan, and to compare the demographic and environmental factors associated with each form of tobacco use.

DESIGN

We surveyed 1845 students randomly recruited from four universities in Jordan. We used multivariable logistic regression controlling for clustering of individuals within universities to determine associations between demographic and environmental covariates and waterpipe tobacco and cigarette use.

RESULTS

Waterpipe tobacco smoking rates were 30% in the past 30 days and 56% ever, while cigarette smoking rates were 29% in the past 30 days and 57% ever. Past 30-day waterpipe tobacco smoking rates were 59% for males and 13% for females. Females had substantially lower odds than males of being current waterpipe (OR 0.12, 95%CI 0.10-0.15) or cigarette (OR 0.08, 95%CI 0.05-0.14) smokers. Current cigarette smoking was more significantly associated with markers of high socio-economic status (SES) than waterpipe tobacco smoking.

CONCLUSION

Waterpipe tobacco smoking is as common as cigarette smoking among Jordanian university students. While cigarette smoking is consistently associated with high SES, waterpipe tobacco smoking is more evenly distributed across various populations.

Impaired neural transmission and synaptic plasticity in superior cervical ganglia from β-amyloid rat model of Alzheimer's disease

Basal synaptic transmission and activity-dependent synaptic plasticity were evaluated in superior cervical sympathetic ganglia (SCG) of amyloid-β rat model of Alzheimer's disease (Aβ rat) using electrophysiological and molecular techniques. Rats were administered Aβ peptides (a mixture of 1:1 Aβ1-40 and Aβ1-42) by chronic intracerebroventricular infusion via 14-day mini-osmotic pumps (300 pmol/day). Control rats received Aβ40-1 (inactive reverse peptide: 300 pmol/day). Ganglionic compound action potentials were recorded before (basal) and after repetitive stimulation. In isolated SCG, ganglionic long-term potentiation (gLTP) was generated by a brief train of stimuli (20Hz for 20s) and ganglionic long-term depression (gLTD) was produced with trains of paired pulses. The input/output (I/O) curves of ganglia from Aβ rats showed a marked downward shift along all stimulus intensities, compared to those of ganglia from control animals, indicating impaired basal synaptic transmission. In addition, repetitive stimulation induced robust gLTP and gLTD in ganglia isolated from control animals, but, the same protocols failed to induce gLTP or gLTD in ganglia from Aβ rats indicating impairment of activity-dependent synaptic plasticity in these animals. Western blotting of SCG homogenate from Aβ rats revealed reduction in the ratio of phosphorylated-/total-CaMKII and in calcineurin protein levels. Although other mechanisms could be involved, these changes in signaling molecules could represent an important molecular mechanism linked to the failure to express synaptic plasticity in Aβ rat ganglia. Results of the current study could explain some of the peripheral nervous system manifestations of Alzheimer's disease.

No correlation exists between vitamin B12 and quality of life in healthy young adult population

BACKGROUND AND OBJECTIVES

Vitamin B12 (B12) is essential for well-being and healthy life, since it plays a critical role in DNA synthesis, hematopoiesis and neurologic function. B12 deficiency remains one of the most common nutrition deficiencies in the world and is associated with increasing risk of cardiovascular disease, cancer, mental health problem, osteoporosis, and defect-birth outcomes. The main objective of this study is to determine the impact of B12 levels on quality of life (QOL) among healthy university students.

MATERIALS AND METHODS

This cross-sectional study involved 359 healthy university students (age 18-30 years) of both genders. Their QOL was as vitamin B12 level was measured using the IMx system (Abbott laboratories IMX, USA).

RESULTS

No correlation was detected between B12 levels and the two major QOL subscales: the Physical Component Summary (PCS) and Mental Component Summary (MCS). Additionally, none of the other eight subscale of the SF-36 was significantly correlated with b12 levels.

CONCLUSION

We conclude that no correlation exists between B12 levels and QOL scores among young adult healthy populations. Further investigations are required to confirm the impact of B12 status on QOL among healthy populations.

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.

Prophylactic use of aspirin does not induce anaemia among adults

BACKGROUND

Aspirin is considered one of the most prescribed drugs worldwide, predominantly for its cardioprotective effects. However, its use may be precluded by gastrointestinal and haematological side-effects.

OBJECTIVE

To investigate the association between the prophylactic use of aspirin and the prevalence of anaemia among adults. Other demographic factors and co-morbid conditions such as kidney or liver failure, diabetes mellitus, hypertension, hyperlipidemia, coronary artery disease, ulcer, ulcer medications, and the use of non-steroidal anti-inflammatory drugs, which might be associated with anaemia, were also investigated.

RESULTS

No association between aspirin use and prevalence of anaemia was observed. Age and smoking were the only factors contributing significantly to the occurrence of anaemia. Moreover, gender, age and the use of peptic ulcer medication were associated with reduced haemoglobin levels.

CONCLUSION

The results may help in minimizing concerns about the development of anaemia among patients on aspirin. They highlight the importance of age, gender, smoking and ulcer medication in determining the incidence of anaemia among those patients.

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.

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.

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.

A critical role of CREB in the impairment of late-phase LTP by adult onset hypothyroidism

We have shown previously that adult onset hypothyroidism impairs late-phase long-term potentiation (L-LTP) and reduces the protein levels of mitogen-activated protein kinases (MAPKp44/42 (ERK1/2)) 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 of the hippocampus. L-LTP was evoked by multiple train high-frequency stimulation (MHFS) in area CA1 of the hippocampus of thyroidectomized and sham control anesthetized adult rats. Immunoblot analysis showed reduction in the basal protein levels of adenylyl cyclase I (ACI), calcium calmodulin-dependent protein kinase IV (CaMKIV), and cyclic-AMP response element-binding protein (CREB; phosphorylated (P-) and total) in hypothyroid rats. A significant increase in the levels of P-CREB, P-MAPKp44 and P-MAPKp42 was seen 4 h after MHFS in sham-operated control animals, but not in hypothyroid animals. The levels of total CREB, total MAPKp44, total MAPKp42 and CaMKIV were elevated in both groups 4 h after MHFS. Our results suggest that in adult hypothyroid rats, the reduced basal level of CaMKIV, MAPKp44/42 and CREB along with the failure of MHFS to induce MAPKp44/42 and CREB phosphorylation may be responsible for L-LTP impairment in the CA1 area during hypothyroidism.

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.

Levothyroxin restores hypothyroidism-induced impairment of LTP of hippocampal CA1: Electrophysiological and molecular studies

Hypothyroidism impairs synaptic plasticity as well as learning and memory. Clinical reports are conflicting about the ability of thyroid hormone replacement therapy to fully restore the hypothyroidism-induced learning and memory impairment. Recently, we have shown that hypothyroidism impairs LTP and cognition in adult rats. We have studied the effect of thyroxin replacement therapy on hypothyroidism-induced LTP impairment using electrophysiological and molecular approaches. Recording from CA1 region of the hippocampus in anesthetized adult rat indicated that 6 weeks of thyroxin replacement therapy (20 microg/kg/day) fully restored LTP impaired by hypothyroidism. Western blotting showed reduction in phosphorylated (P)-CAMKII, total-CaMKII, neurogranin, and calmodulin basal levels in the CA1 region of the hippocampus of hypothyroid rats. The levels of these molecules were normalized by thyroxin replacement therapy. The hypothyroid-induced elevation of basal calcineurin levels and activity was also normalized by thyroxin treatment. However, thyroxin replacement therapy did not restore hypothyroidism-induced reduction in PKCgamma basal protein levels. Additionally, real-time PCR, showed a reduction in basal neurogranin mRNA level that was normalized by thyroxin replacement therapy. In the sham (control) rats, induction of LTP by high-frequency stimulation increases P-CaMKII, and total CaMKII levels as well as CaMKII phosphotransferase activity. However, in hypothyroid rats, the same stimulation protocol induced an increase only in total-CaMKII. Thyroxin treatment normalized the levels and activity of these molecules. The results demonstrated that thyroxin therapy normalized the electrophysiological and molecular effects of hypothyroidism on the CA1 region and emphasized the critical role P-CaMKII plays in hypothyroidism-induced LTP impairment.

Role of phosphorylated CaMKII and calcineurin in the differential effect of hypothyroidism on LTP of CA1 and dentate gyrus

Hypothyroidism impairs early long-term potentiation (LTP) in the CA1 but not in the dentate gyrus (DG) of hippocampus of anesthetized adult rats. Protein levels and activities of signaling molecules in both the CA1 and DG of surgically thyroidectomized and sham-operated euthyroid rats were measured. Basal levels of total calmodulin kinase II (CaMKII) protein in both the CA1 and DG were decreased in hypothyroidism. Marked reduction of basal P-CaMKII levels and CaMKII activity was seen in CA1, but not in the DG of the same hypothyroid animals. Basal levels of calmodulin and protein kinase Cgamma (PKCgamma) were decreased in CA1 but remained unchanged in the DG of hypothyroid rats. Basal calcineurin levels and activity, although enhanced in CA1, were reduced in the DG of hypothyroid rats. These findings suggest that the DG may possess a compensatory mechanism whereby calcineurin levels are reduced, to allow sufficient CaMKII activity to produce an apparently normal LTP in hypothyroid rats.

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.