Abdur Rahman

The Excitotoxin Quinolinic Acid Induces Tau Phosphorylation in Human Neurons

Some of the tryptophan catabolites produced through the kynurenine pathway (KP), and more particularly the excitotoxin quinolinic acid (QA), are likely to play a role in the pathogenesis of Alzheimers disease (AD). We have previously shown that the KP is over activated in AD brain and that QA accumulates in amyloid plaques and within dystrophic neurons. We hypothesized that QA in pathophysiological concentrations affects tau phosphorylation. Using immunohistochemistry, we found that QA is co-localized with hyperphosphorylated tau (HPT) within cortical neurons in AD brain. We then investigated in vitro the effects of QA at various pathophysiological concentrations on tau phosphorylation in primary cultures of human neurons. Using western blot, we found that QA treatment increased the phosphorylation of tau at serine 199/202, threonine 231 and serine 396/404 in a dose dependent manner. Increased accumulation of phosphorylated tau was also confirmed by immunocytochemistry. This increase in tau phosphorylation was paralleled by a substantial decrease in the total protein phosphatase activity. A substantial decrease in PP2A expression and modest decrease in PP1 expression were observed in neuronal cultures treated with QA. These data clearly demonstrate that QA can induce tau phosphorylation at residues present in the PHF in the AD brain. To induce tau phosphorylation, QA appears to act through NMDA receptor activation similar to other agonists, glutamate and NMDA. The QA effect was abrogated by the NMDA receptor antagonist memantine. Using PCR arrays, we found that QA significantly induces 10 genes in human neurons all known to be associated with AD pathology. Of these 10 genes, 6 belong to pathways involved in tau phosphorylation and 4 of them in neuroprotection. Altogether these results indicate a likely role of QA in the AD pathology through promotion of tau phosphorylation. Understanding the mechanism of the neurotoxic effects of QA is essential in developing novel therapeutic strategies for AD.

Phosphothreonine-212 of Alzheimer Abnormally Hyperphosphorylated Tau is a Preferred Substrate of Protein Phosphatase-1

We isolated and characterized several phosphoseryl/phosphothreonyl phosphatase activities (P1–P11) from frontal lobe of six autopsied human brains. Of these, PP1 (P3) was a major tau phosphatase. The enzyme required metal ions and was maximally activated by Mn2+. Western blots with antibodies to known protein phosphatases showed PP1 and PP2B immunoreactivity. However, the removal of PP2B by immunoabsorption or its inhibition with EGTA did not result in appreciable loss of P3 activity. These observations suggest that P3 was an enriched PP1. Dephosphorylation of Alzheimer disease hyperphosphorylated tau (AD P-tau) by PP1 was site-specific. PP1 preferentially dephosphorylated pT212 (40%), pT217 (26%), pS262 (33%), pS396 (42%) and pS422 (31%) of AD P-tau. Dephosphorylation of tau at pT181, pS199, pS202, pT205, pS214, and pS404, was undetectable. Of the sites dephosphorylated, pT212 was only a substrate for PP1, as purified/enriched PP2A and PP2B from the same brains did not dephosphorylate this site.

Association of maternal blood lead level during pregnancy with child blood lead level and pregnancy outcome in Kuwait.

High blood lead levels (BLL) in pregnancy are associated with poor pregnancy outcome and neuro-behavioral deficits in infants. We investigated the prevalence of high BLL in pregnant women and its impact on pregnancy outcome in Kuwait. Blood from 194 mother–infant pairs were analyzed for lead by Atomic Absorption Spectrophotometry. Data were collected on birth weight, crown–heel length, head circumference, APGAR score, gestational age, and placental weight. Results revealed that 28% of pregnant women and 58% of infants had BLL >10 g/dL. Cord BLL was significantly higher than maternal BLL (10.92 vs. 5.77 g/dL, p < .001). Maternal BLL was not significantly associated with any of the outcome variables tested, whereas, cord BLL was a significant negative predictor of APGAR score only in boys. A significant proportion of pregnant women and their children in Kuwait have lead levels well above the safety limit, which is a matter of public health concern.

Developmental Vitamin D Deficiency Affects Spatial Learning in Wistar Rats

Background: Vitamin D deficiency is a global problem. Recent evidence suggests that vitamin D is involved in brain development and function. Vitamin D deficiency has been associated with poor cognitive function in adults, but the effect of developmental vitamin D deficiency (DVDD) on cognitive function and brain development in children has not been well established.Objective: We explored the effects of DVDD on cognitive functions and brain morphology of rat pups.Methods: Wistar rat pups born to control and vitamin D-deficient dams were divided into 4 groups: control (C), deficient during gestation (dG), deficient during lactation (dL), and deficient during gestation and lactation (dGL). Spatial learning and memory were assessed by the Morris water maze test at postnatal day (PND) 24 and PND 45. Cortical thickness at the level of the hippocampus was measured at PND 63, and synapses were counted in specified areas of the hippocampus at PND 32 and PND 63.Results: Repeated-measures ANOVA revealed that at PND 24, learning (escape latency) was impaired (by 42%) in the dGL group, whereas at PND 45, both the dL and the dGL groups showed learning impairment (by 47% and 45%, respectively) compared with their respective C groups (P < 0.05). Short-term or long-term memory was largely unaffected by DVDD either at PND 24 or PND 45. Compared with the C group, all the DVDD groups had fewer synapses in the molecular layer of the hippocampus (P < 0.001). The synapse number decreased by 54% in the dGL group at PND 33 and by 70% in the dL and dGL groups at PND 63. All the DVDD groups at PND 63 showed a reduced cortical thickness (by 22%) compared with the C group (P < 0.05).Conclusion: These results suggest that a combined prenatal and postnatal DVDD for ≥6 wk in rat pups affects learning but not memory.

Exposure to low level of lead during preweaning period increases metallothionein-3 expression and dysregulates divalent cation levels in the brain of young rats

HighlightsLead exposure during the preweaning period increased the expression of MT‐3 in the brain of Wistar rats.MT‐3 protein was significantly increased in both the cerebrum and in hippocampus of lead‐exposed rats.MT‐3 gene expression was also increased in both the cerebrum and in the hippocampus in the lead‐exposed rats.Increased MT‐3 positive cells were observed in the cortex and in the CA1and the dentate gyrus regions of the hippocampus.Lead exposure decreased the levels of copper, zinc and manganese in the blood and brain of young rats. ABSTRACT Lead (Pb) is a neurotoxic heavy metal, but the mechanism of its neurotoxicity is not clearly understood. Expression of metallothioneins (MTs) is induced in response to heavy metal exposure as a protective mechanism against heavy metal toxicity. There are several isoforms of MTs (MT‐1 to 4), of which MT‐3 is the neuron specific isoform, which also has neurite growth inhibitory effects. Whereas, the induction of MT‐1 and 2 in response to Pb has been reported, the effect of Pb on the expression of MT‐3 in the brain has not been documented. This study aimed at investigating the effect of Pb exposure on the expression of MT‐3 in the cerebrum and hippocampus. Wistar rat pups were exposed to Pb via their dams’ drinking water (0.2% lead acetate in deionized water) from postnatal day (PND) 0 to 21 and directly via drinking water until PND30. Expression of MT‐3 was measured by Western blot and quantitative RT‐PCR. MT‐3 localization was done by immunohistochemistry. Divalent metal ions were analysed by atomic absorption spectrophotometry. Levels of Pb in blood and cerebrum were significantly increased, while that of copper (Cu), zinc (Zn) and manganese (Mn) were significantly decreased in the Pb‐exposed rats at both PND21 and PND30. MT‐3 protein was significantly increased in the cerebrum (by 2.5‐fold) and in hippocampus (1.4 to 3.2‐fold) in both PND21 and PND30 Pb‐exposed rats over controls. MT‐3 gene expression also increased in the cerebrum (by 42%), and in the hippocampus (by 65% and 43% in the PND21 and PND30 rats, respectively), in the Pb‐exposed rats over controls, but the increase was statistically significant (p < 0.05) only in the PND30 rats. Pb exposure significantly increased (p < 0.05) percentage of MT‐3 immunoreactive cells in Cornu Ammonis and dentate gyrus regions in the PND21 rats, and in the Cornu Ammonis 1, dentate gyrus and cortex regions in the PND30 rats. Our data thus provide convincing evidence that exposure to low levels of Pb during preweaning period increases the expression of MT‐3 in the brain of rats.

Vitamin D status among adolescents in Kuwait: a cross-sectional study

Objectives In Kuwait, as in many Arab states in the Gulf region, there are limited data on the prevalence of vitamin D deficiency among healthy adolescents. This study aimed to estimate the prevalence of vitamin D deficiency in a nationally representative sample of adolescents and investigate factors associated with vitamin D status. Methods A cross-sectional study was conducted on 1416 adolescents aged 11–16 years, who were randomly selected from middle schools in all governorates of Kuwait. Data were collected from parents through self-administered questionnaire and from adolescents through face-to-face interview. Vitamin D was measured using liquid chromatography-tandem mass spectrometry. Logistic regression was used to investigate the independent factors associated with vitamin D status. Results The prevalence of vitamin D deficiency was 81.21% (95% CI 71.61% to 90.81%), while severe deficiency was 39.48%. Only 3.60% of adolescents were vitamin D-sufficient. The prevalence of vitamin D deficiency was significantly higher among girls compared with boys (91.69% vs 70.32%; p<0.001). There was a significant inverse correlation between vitamin D and parathyroid hormone (Spearman correlation=−0.35; p<0.001). In the final model, gender, age, governorate, parental education, body mass index, vitamin D supplement and the number of times adolescents walk to schools per week were all significantly related to vitamin D deficiency. Conclusion High prevalence of vitamin D deficiency was noted among adolescents in Kuwait despite the abundant sunshine, which may reflect strong sun avoidance behaviour. Adequate outdoor daytime activities should be encouraged especially for girls. We call for locally tailored guidelines for vitamin D supplement in which girls should have a higher dose compared with boys.

Plasma 25-Hydroxy Vitamin D Is Not Associated with Either Cognitive Function or Academic Performance in Adolescents

Several observational studies have reported an association between low levels of vitamin D (VD) and poor cognition in adults, but there is a paucity of data on such an association in adolescents. We investigated the association between VD and cognitive function or academic achievement among 1370 adolescents, who were selected from public middle schools in Kuwait, using stratified multistage cluster random sampling with probability proportional to size. Plasma 25-hydroxy VD (25-OH-D) was measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS). An age-adjusted standard score (ASC), calculated from Raven’s Standard Progressive Matrices test, was used to evaluate cognitive function; academic achievements were extracted from the schools’ records. Data on various covariates were collected from the parents through a self-administered questionnaire and from the adolescents using face-to-face interviews. 25-OH-D was weakly correlated positively with ASC (ρ = 0.06; p = 0.04). Univariable linear regression analysis showed an association between 25-OH-D categories and ASC after adjusting for gender, but adjusting for parental education was sufficient to explain this association. Multivariable analysis showed no association between 25-OH-D and ASC after adjusting for potential confounders whether 25-OH-D was fitted as a continuous variable (p = 0.73), a variable that is categorized by acceptable cutoff points (p = 0.48), or categorized into quartiles (p = 0.88). Similarly, 25-OH-D was not associated with academic performance. We conclude that 25-OH-D is associated with neither cognitive function nor academic performance in adolescents.

Plasma 25-Hydroxy Vitamin D is not Associated with Acne Vulgaris

Few studies have investigated the association between Acne vulgaris (AV) and vitamin D level. In this study we aimed to investigate the association between 25-hydroxyvitamin D (25-OH-VitD) level and AV in a country with plenty of sunshine. A cross-sectional study was conducted on 714 adolescents who were randomly selected from public schools using multistage cluster random sampling with probability proportional to size. 25-OH-VitD levels were measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The Global Acne Grading System (GAGS) was used to assess the severity of AV. Data on potential confounders were collected from the parents through a self-administered questionnaire, and from the adolescents using a face-to-face interview. Of 714 participants, 351 (41.16%) were males. The mean (standard deviation (SD)) age was 12.28 (0.81) years. AV was observed in 479 (67.1%) adolescents. There was no significant association between 25-OH-VitD level and clinically assessed AV before or after adjusting for potential confounders. This was consistent whether 25-OH-VitD was fitted as a continuous variable or categorized using acceptable cutoff points or tertiles. In this study vitamin D status was not associated with AV, therefore our data do not support vitamin D supplementation either to treat or to prevent AV.

Lead Affects Vitamin D Metabolism in Rats

A negative association between blood lead and vitamin D concentrations has been reported, however, experimental data on the effect of lead (Pb) on vitamin D metabolism is scarce. We investigated the effects of Pb on serum vitamin D metabolites, vitamin D activating enzymes and vitamin D receptor (VDR) in rats. Newborn Wistar rat pups were exposed to 0.2% Pb-acetate via their dams’ drinking water from post-natal day (PND) 1 to 21 and directly in drinking water until PND30. Serum 25-hydroxyvitamin D was analyzed with LC-MS/MS and 1,25-dihydroxyvitamin D with an immunoassay. Tissue expression of vitamin D activating enzymes and VDR were measured by Western blot and immunohistochemistry. Serum 25-hydroxyvitamin D was significantly decreased at both PND21 and PND30, whereas 1,25-dihydroxyvitamin D was decreased (p < 0.05) only at PND21 in the Pb-exposed rats. Expression of renal 1-α-hydroxylase was decreased by Pb only at PND21 (p < 0.05) but the brain 1-α-hydroxylase was not affected. Hepatic 25-hydroxylase expression was significantly decreased at PND21 but significantly increased at PND30 by Pb exposure. VDR expression in the brain was increased at both PND21 and PND30 (p < 0.05). These results suggest that Pb interferes with vitamin D metabolism by affecting the expression of its metabolizing enzymes.

Pregnancy outcome variables and associated factors in different nationalities living in Kuwait

This study aimed to investigate differences in pregnancy outcome among various nationalities residing in Kuwait. Cross-sectional data were collected from 369 mother-infant dyads at delivery on mother height (MH), mother haemoglobin (mHb), child haemoglobin (cHb), mid-upper arm circumference (MUAC), gestational age (GA), placental weight (PW), birth weight (BW), crown-heal length (CHL), and head circumference (HC). Significant differences among various nationalities were observed in mHb, HC, CHL, PW and MH. Kuwaiti and Indian women had lower PW and their babies had lower HC and CHL. Prevalence of anaemia (Hb <11.0 g/dL) ranged from 7.1% (Lebanese) to 30.0% (Kuwaiti) with the overall prevalence of 19.5%. Prevalence of low birth weight was 3.5%. Multiple linear regression analysis revealed PW as a significant predictor of BW, CHL and HC. Significant differences among various nationalities were observed in mHb, HC, CHL, PW and MH.The significance of these differences and their contributing factors needs further research.