Elevated Blood Lead Concentrations in Essential Tremor: A Case–Control Study in Mersin, Turkey

Essential tremor (ET) is one of the most common neurologic disorders. Aside from underlying susceptibility genes, recent studies have also begun to focus on environmental toxic factors. Yet there remains a paucity of information on such factors, making studies of environmental factors important. A recent study in New York City found blood lead concentrations to be elevated in ET cases compared with matched controls. Chronic exposure to lead produces cerebellar damage, and this could predispose individuals to develop ET

Association between essential tremor and blood lead concentration

Lead is a ubiquitous toxicant that causes tremor and cerebellar damage. Essential tremor (ET) is a highly prevalent neurologic disease associated with cerebellar involvement. Although environmental toxicants may play a role in ET etiology and their identification is a critical step in disease prevention, these toxicants have received little attention. Our objective was to test the hypothesis that ET is associated with lead exposure. Therefore, blood lead (BPb) concentrations were measured and a lifetime occupational history was assessed in ET patients and in controls. We frequency matched 100 ET patients and 143 controls on age, sex, and ethnicity. BPb concentrations were analyzed using graphite furnace atomic absorption spectrophotometry. A lifetime occupational history was reviewed by an industrial hygienist. BPb concentrations were higher in ET patients than in controls (mean ± SD, 3.3 ± 2.4 and 2.6 ± 1.6 µg/dL, respectively; median, 2.7 and 2.3 µg/dL; p = 0.038). In a logistic regression model, BPb concentration was associated with diagnosis [control vs. ET patient, odds ratio (OR) per unit increase = 1.21; 95% confidence interval (CI), 1.05-1.39; p = 0.007]. BPb concentration was associated with diagnosis (OR per unit increase = 1.19; 95% CI, 1.03-1.37; p = 0.02) after adjusting for potential confounders. Prevalence of lifetime occupational lead exposure was similar in ET patients and controls. We report an association between BPb concentration and ET. Determining whether this association is due to increased exposure to lead or a difference in lead kinetics in ET patients requires further investigation

Prenatal Cocaine Exposure Uncouples mGluR1 from Homer1 and Gq Proteins

Cocaine exposure during gestation causes protracted neurobehavioral changes consistent with a compromised glutamatergic system. Although cocaine profoundly disrupts glutamatergic neurotransmission and in utero cocaine exposure negatively affects metabotropic glutamate receptor-type 1 (mGluR1) activity, the effect of prenatal cocaine exposure on mGluR1 signaling and the underlying mechanism responsible for the prenatal cocaine effect remain elusive. Using brains of the 21-day-old (P21) prenatal cocaine-exposed rats, we show that prenatal cocaine exposure uncouples mGluR1s from their associated synaptic anchoring protein, Homer1 and signal transducer, Gq/11 proteins leading to markedly reduced mGluR1-mediated phosphoinositide hydrolysis in frontal cortex (FCX) and hippocampus. This prenatal cocaine-induced effect is the result of a sustained protein kinase C (PKC)-mediated phosphorylation of mGluR1 on the serine residues. In support, phosphatase treatment of prenatal cocaine-exposed tissues restores whereas PKC-mediated phosphorylation of saline-treated synaptic membrane attenuates mGluR1 coupling to both Gq/11 and Homer1. Expression of mGluR1, Homer1 or Gα proteins was not altered by prenatal cocaine exposure. Collectively, these data indicate that prenatal cocaine exposure triggers PKC-mediated hyper-phosphorylation of the mGluR1 leading to uncoupling of mGluR1 from its signaling components. Hence, blockade of excessive PKC activation may alleviate abnormalities in mGluR1 signaling and restores mGluR1-regulated brain functions in prenatal cocaine-exposed brains