Influence of morphine on levels of type Ⅱ inhibitory guanine nucleotide binding protein in primary hippocampal neurons

BACKGROUND： The pharmacological action of opioid drugs is related to signal transduction of inhibitory guanine nucleotide binding protein. OBJECTIVE： To quantitatively and qualitatively analyze the influence of morphine on levels of type Ⅱ inhibitory guanine nucleotide binding protein （Gi2 protein） in primary cultured hippocampal neurons at different time points. DESIGN, TIME AND SETTING： A randomized controlled study, which was performed at the Department of Neurobiology, Changzheng Hospital, Second Military Medical University of Chinese PLA between September 2002 and March 2004. MATERIALS： Cerebral hippocampal neurons were obtained from newborn SD rats at 1 2 days of age. Biotin-antibody Ⅱ-avidin fluorescein isothiocyanate （Avidin-FITC） was purchased from Sigma Company （USA） and the Gi2 protein polyclonal antibody from Santa Cruz Biochemistry Company （USA）. METHODS： Seven days after culture, mature hippocampal neurons were randomly divided into six groups： 4-, 8-, 16-, 24-, and 48-hour morphine groups, and a blank control group. Neurons in the morphine groups received morphine （10 μ mol/L）, which could cause alterations of G-protein mRNA and cAMP expression in the prefrontal cortex. Neurons in the blank control group were given the same volume of saline. MAIN OUTCOME MEASURES： Gi2 protein levels were detected by an immunofluorescence technique, and were analyzed by the image analytic system with the use of green fluorescence intensity. RESULTS： Gi2 protein levels in hippocampal neurons gradually decreased in the 4-, 8-, 16-, 24-, and 48-hour morphine groups. In particular, Gi2 protein levels in the 16-, 24-, and 48-hour morphine groups were significantly lower than that in the blank control group （P 〈 0.05 0.01）. CONCLUSION： Morphine may decrease Gi2 protein level in primary hippocampal neurons, and the decreasing trend is positively related to morphine-induced time.

Downregulation of signal transduction and STAT3 expression exacerbates oxidative stress mediated by NLRP3 inflammasome

Activated nucleotide binding to the oligonucleotide receptor protein 3（NLRP3） inflammasome is possibly involved in the pathogenesis of Alzheimer＇s disease through oxidative stress and neurogenic inflammation. Low expression of the signal transducer and activator of transcription 3（STAT3） gene may promote the occurrence of neurodegenerative diseases to some extent. To clarify the roles of the NLRP3 inflammasome and STAT3 expression in oxidative stress,（1） SHSY5 Y cells were incubated with 1 mM H2 O2 to induce oxidative stress injury, and the expression of human-cell-specific signal transduction, STAT3-shRNA silencing signal transduction and STAT3 were detected. Cells were pretreated with Ca2＋ chelator BAPATA-AM（0.1 mM） for 30 minutes as a control.（2） Western blot assay was used to analyze the expression of caspase-1, NLRP3, signal transduction and STAT3. Enzyme-linked immunosorbent assay was used to analyze interleukin-1β levels. Flow cytometry was carried out to calculate the number of apoptotic cells. We found that H2 O2 treatment activated NLRP3 inflammasomes and decreased phosphorylation of signal transduction and STAT3 serine 727. BAPTA-AM pretreatment abolished the H2 O2-induced activation of NLRP3 inflammasomes, caspase-1 expression, interleukin-1β expression and apoptosis in SHSY5 Y cells, and had no effect in cells with downregulated STAT3 expression by RNAi. The findings suggest that downregulation of signal transduction and STAT3 expression may enhance the oxidative stress mediated by NLRP3, which may not depend on the Ca2^＋ signaling pathway.

Genetic variants in the ADD1 and GNB3 genes and bloodpressure response to potassium supplementation

Dietary potassium-supplementation has been associated with a decreased risk of hypertension and other cardiovascular outcomes.However,blood pressure(BP)responses to potassium supplementation vary among individuals.This study was designed to examine the association between 12 single nucleotide polymorphisms(SNPs)in the adducin 1 alpha(ADD1)and guanine nucleotide binding protein(G protein)beta polypeptide 3(GNB3)genes and systolic BP(SBP),diastolic BP(DBP),and mean arterial pressure(MAP)responses to potassium-supplementation.We conducted a 7-day high-sodium intervention(307.8 mmol sodium/day)followed by a 7-day high-sodium with potassium-supplementation(60 mmol potassium/day)among 1906 Han Chinese participants from rural north China.BP measurements were obtained at the end of each intervention period using a random-zero sphygmomanometer.We identified significant associations between ADD1 variant rs17833172 and SBP,DBP,and MAP responses to potassium-supplementation(all P<0.0001)that remained significant after adjustment for multiple comparisons.In participants that were heterozygous or homozygous for the G allele of this marker,SBP,DBP,and MAP response to potassium-supplementation were–3.52(–3.82,–3.21),–1.41(–1.66,–1.15)and–2.12(–2.37,–1.87),respectively,as compared to the corresponding responses of 1.99(0.25,3.73),–0.65(–0.10,–0.21),and–0.23(–0.37,0.83),respectively,for those who were homozygous for A allele.In addition,participants with at least one copy of the G allele of rs12503220 of the ADD1 gene had significantly increased DBP and MAP response to potassium-supplementation(P=0.0041 and 0.01,respectively),which was also significant after correction for multiple testing.DBP and MAP responses to potassiumsupplementation were–1.36(–1.63,–1.10)and–2.07(–2.32,–1.82)for those with at least G allele compared to corresponding responses of 0.86(–0.68,2.40)and–0.45(–1.74,0.84)for those who were homozygous for A allele.In summary,our study identified novel associations between genetic variants of the ADD1 gene and BP response to potassium-supplementation,which could have important clinical and public health implications.Future studies aimed at replicating these novel findings are warranted.