Aim To investigate the regulatory mecha-nisms of donepezil on the expression and enzymatic ac-tivity of cytochrome P450 3A4(CYP3A4),elucidate the synergistic impact of hypoxia on CYP3A4 function,and reveal its potential association with drug-induced cardiotoxicity,particularly QT interval prolongation.Methods Western blot,co-immunoprecipitation,and gene knockdown techniques were employed to evaluate the effects of donepezil and hypoxia on CYP3A4 pro-tein expression.CYP3A4 enzymatic activity was as-sessed using an in vitro incubation system with rat liver microsomes combined with high-performance liquid chromatography(HPLC),and the half-maximal inhib-itory concentration(IC50)was determined.Results Donepezil(10 μmol·L-1)and hypoxia reduced CYP3A4 protein expression to 31.75％and 45.90％of the control levels,respectively.Both interventions activated the gp78-mediated ubiquitin-proteasome path-way,significantly increasing CYP3A4 ubiquitination levels by 2.1-fold compared to the control group,thereby promoting proteasomal degradation.Donepezil inhibited CYP3A4 enzyme activity with an IC50 of 83.4μmol·L-1,and hypoxia synergistically enhanced this inhibitory effect,reducing the IC50 to 20.79 μmol·L-1.Conclusion Donepezil downregulates CYP3A4 function through dual mechanisms involving ubiquitin-mediated proteasomal degradation and direct enzymatic inhibition.Hypoxia potentiates this effect,leading to impaired metabolism of CYP3A4 substrate drugs,ele-vated plasma drug concentrations(1.6-2.3-fold in-crease compared to normal metabolic conditions),and an increased risk of QT interval prolongation and other forms of cardiotoxicity.

Aim To investigate the regulatory mecha-nisms of donepezil on the expression and enzymatic ac-tivity of cytochrome P450 3A4(CYP3A4),elucidate the synergistic impact of hypoxia on CYP3A4 function,and reveal its potential association with drug-induced cardiotoxicity,particularly QT interval prolongation.Methods Western blot,co-immunoprecipitation,and gene knockdown techniques were employed to evaluate the effects of donepezil and hypoxia on CYP3A4 pro-tein expression.CYP3A4 enzymatic activity was as-sessed using an in vitro incubation system with rat liver microsomes combined with high-performance liquid chromatography(HPLC),and the half-maximal inhib-itory concentration(IC50)was determined.Results Donepezil(10 μmol·L-1)and hypoxia reduced CYP3A4 protein expression to 31.75％and 45.90％of the control levels,respectively.Both interventions activated the gp78-mediated ubiquitin-proteasome path-way,significantly increasing CYP3A4 ubiquitination levels by 2.1-fold compared to the control group,thereby promoting proteasomal degradation.Donepezil inhibited CYP3A4 enzyme activity with an IC50 of 83.4μmol·L-1,and hypoxia synergistically enhanced this inhibitory effect,reducing the IC50 to 20.79 μmol·L-1.Conclusion Donepezil downregulates CYP3A4 function through dual mechanisms involving ubiquitin-mediated proteasomal degradation and direct enzymatic inhibition.Hypoxia potentiates this effect,leading to impaired metabolism of CYP3A4 substrate drugs,ele-vated plasma drug concentrations(1.6-2.3-fold in-crease compared to normal metabolic conditions),and an increased risk of QT interval prolongation and other forms of cardiotoxicity.

OBJECTIVETo investigate the current smoking regulations and their impacts on the environmental tobacco smoke (ETS) levels inside restaurants and bars in Beijing.

METHODSTelephone survey was used to investigate the smoking regulations. TSI Sidepak AM510 was used to measure the level of fine particles less than 2.5 microns in diameter (PM2.5) in restaurants and bars. Analysis of variance and non-parametric rank tests were used to examine the association between indoor and outdoor PM2.5 levels and (1) smoking regulations; and (2) types of restaurants and bars.

RESULTSOf the 305 restaurants and bars surveyed, 27.9% had complete or partial smoking prohibiting rules. The average indoor PM2.5, level of the 92 restaurants and bars was 253.08 microg/m3 , 102.37% higher than the outdoor level. The average indoor and outdoor PM2.5 levels in the restaurants and bars with smoking ban regulations were 93.10 microg/m3 and 110.33 microg/m3 whole 289.34 microg/m3 and 128.40 microg/m3 in those without, respectively. The average indoor and outdoor PM2.5 levels of bars were 413.46 microg/m3 and 190.62 microg/m3, respectively, while in the western fast-food restaurants, they were 83.86 microg/m3 and 104.77 microg/m3, respectively. The outdoor PM2.5 levels were higher than the indoor levels in different classes of restaurants and bars. Furthermore, there was a significant positive correlation between PM2.5 levels and the number of smokers per cube meters (r = 0.47, P < 0.001).

CONCLUSIONSmoking regulations could effectively reduce the ETS level in restaurants and bars.

Air Pollution, Indoor ; analysis ; legislation & jurisprudence ; China ; Environmental Monitoring ; Particulate Matter ; analysis ; Restaurants ; Smoking ; legislation & jurisprudence ; Tobacco Smoke Pollution ; analysis ; legislation & jurisprudence