Effect modification by aging on the associations of nicotine exposure with cognitive impairment among Chinese elderly

Active and passive exposure to tobacco smoke may increase risk of cognitive decline. However, effects of enhanced the aging process on the association of urinary nicotine metabolites with cognitive impairment remain unclear. In this study, 6657 Chinese older adults completed the physical examinations and cognitive tests. We measured urinary nicotine metabolite levels, mitochondrial DNA copy number (mtDNA-CN), and relative telomere length (RTL) and analyzed effects of urinary nicotine metabolites and their interaction with mtDNA-CN or RTL on cognitive impairment by generalized linear models and qg-computation, respectively. Each 1-unit increase in urinary 3-OHCot, 3-OHCotGluc, CotGluc, or NicGluc levels corresponded to a 1.05-, 1.09-, 1.04-, and 0.90-fold increased risk of cognitive impairment. Each 1-quantile increment in the mixture level of 8 nicotine metabolites corresponded to an increment of 1.40- and 1.34-fold risk of cognitive impairment in individuals with longer RTL or low mtDNA-CN. Urinary 3-OHCotGluc and RTL or mtDNA-CN exhibited an additive effect on cognitive impairment in addition to the mixture of 8 nicotine metabolites and mtDNA-CN. The findings suggested that aging process may increase the risk of tobacco-related cognitive impairment.

Non-linear dose-response relation between urinary levels of nicotine and its metabolites and cognitive impairment among an elderly population in China

BACKGROUND

Active smoking and exposure to environmental tobacco smoke may be related to cognitive function decline. We assessed the associations of urinary levels of nicotine and its metabolites with cognitive function.

METHODS

A total of 553 elder adults at high risk of cognitive impairment and 2212 gender- and age-matched individuals at low risk of cognitive impairment were selected at a ratio of 1: 4 from the remained individuals (n = 6771) who completed the baseline survey of the Shenzhen Ageing-Related Disorder Cohort, after excluding those with either Alzheimer's disease, Parkinson's syndrome or stroke as well as those with missing data on variables (including active and passive smoking status, Mini-Cog score). Urinary levels of nicotine and its metabolites and cognitive function for all individuals were measured by high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) and assessed using the Mini-Cog test, respectively. Associations of urinary levels of nicotine and its metabolites with cognitive function were analyzed by conditional logistic regression models.

RESULTS

Individuals in the highest tertile of urinary OHCotGluc (OR: 1.52, 95%CI: 1.19-1.93) or NNO (OR: 1.50, 95%CI: 1.16-1.93) levels as well as in the second tertile of urinary ∑Nic level (OR: 1.43, 95%CI: 1.13-1.82) were at higher risk of cognitive impairment compared with those in the corresponding lowest tertile. Restricted cubic spline models revealed the non-linear dose-response relationships between urinary levels of OHCotGluc, NNO or ∑Nic and the risk of cognitive impairment.

CONCLUSIONS

Urinary levels of OHCotGluc, NNO or ∑Nic exhibited a non-linear dose-response relationship with cognitive function in the urban elderly.

[Accelerated angiotensinogen gene expression in the rat brain made tolerant to morphine or electroacupuncture stimulation]

The aim of the present study was to explore whether the expression of angiotensinogen (Ang) gene was accelerated during the development of morphine tolerance or electroacupuncture tolerance. The total rat brain RNA was extracted by phenol, and dot blot hybridization with synthetic Ang oligo-DNA was adopted for measuring Ang mRNA. Autoradiographic examination revealed a marked increase in Ang mRNA in rats receiving multiple injections of morphine or continuous electroacupuncture (EA) stimulation for several hours. The integrated O.D. (I.O.D.) of the hybridized dots revealed a 1-fold and 8-fold increase in Ang mNRA in rats receiving morphine injection for 1 and 4 days, respectively, and a 5-fold and 13-fold increase in rats receiving 3 and 6h EA stimulation, respectively. The results suggest that transcription of Ang gene in rat brain can be accelerated within 3-4h by continuous morphine or EA stimulation and that a longer lasting stimulation resulted in a stronger gene expression.

[The content of tyrosine in rat luteal cell and the changes caused by hCG, cAMP and progesterone]

The ovaries taken from the immature female rats primed with PMSG-hCG were digested with collagenase-DNAase solution to obtain the luteal cell suspensions. Luteal cells were then incubated with different doses of hCG, cAMP or progesterone for 1.5 hours. The contents of tyrosine in luteal cell suspensions were determined by thin layer chromatogram using dual-wavelength chromatogram scanner. It was found that the content of tyrosine in rat luteal cell suspensions was 1.41 + 0.24 nmol/L/10(6) cells after one hour incubation. hCG, cAMP and progesterone all could significantly increase the content of tyrosine in the suspensions, suggesting the release of "endogenous tyrosine". The increase of tyrosine was not due to increased transformation of phenylalanine, the precursor of tyrosine, and increased protein synthesis, because both phenylalanine and cycloheximide failed to influence such increase.

[3H]tyrosine binding to plasma membrane preparation of rat corpora lutea

Plasma membrane preparations of rat corpora lutea have been incubated with [3H]tyrosine. [3H]tyrosine binding sites are demonstrated and Scatchard analysis shows that there exist two types of binding sites, one with high affinity and low capacity, the other with low affinity and high capacity. The kinetics studies demonstrate that the [3H]tyrosine binding to the two types of binding sites is reversible and the speed of binding to the high affinity type is faster than that to the low affinity type. The analysis of the chemical structure of tyrosine analogues and related compounds with respect to the specificity of the binding sites reveal that both types of binding sites show specificity, but the specificity of the high affinity sites is higher than that of the low affinity sites. The relations of tyrosine structure to binding processing and to tyrosine inhibitory action on hCG-induced progesterone production are discussed. It is suggested that the high affinity binding sites might be regarded as "tyrosine receptors" and the low affinity ones glycoprotein carriers for tyrosine across the plasma membrane.

Some factors affecting [3H]tyrosine binding to plasma membrane preparation of rat corpora lutea in vitro

Temperature, pH, enzymes and ions affected the two types of [3H]tyrosine binding sites differently. The optimal temperature and pH for the high affinity sites were 24 C and 7.4, and for the low affinity sites 37 degrees C and 7.0, respectively. The [3H]tyrosine binding to the high and low affinity sites was not observed at 55 degrees C, nor at pH 6.0 or pH 8.5. Trypsin reduced [3H]tyrosine binding to the high affinity sites, but had no effect on the binding to the low affinity sites. Neuraminidase reduced [3H]tyrosine binding to the low affinity sites, but had no effect on the binding to the high affinity sites. None of cycloheximide, kCG, cAMP, and progesterone affected [3H]tyrosine binding.