BACKGROUND:Curcumin is the main active ingredient of turmeric and has significant medicinal value in anti-tumor,anti-inflammatory,antioxidant and other aspects.However,its poor water solubility,unstable chemical properties and easy decomposition lead to difficulty in extracting curcumin and low extraction yield.Therefore,it is particularly important to optimize the curcumin extraction method.OBJECTIVE:To enhance the extraction yield and utilization value of curcumin and optimize the curcumin extraction process and curcumin nanoparticle preparation process.METHODS:Curcumin was extracted from turmeric by ethanol extraction,ultrasonic extraction,ionic liquid extraction,enzyme extraction,and ionic liquid combined with ultrasonic assisted enzyme extraction.The curcumin extraction yield was detected by high performance liquid chromatography;the best extraction method was determined,and subsequent process optimization experiments were carried out.The curcumin extraction yield was the response value with the type of ionic liquid,reaction temperature,ultrasonic time,liquid-to-solid ratio,ionic liquid concentration,and enzyme-drug mass ratio as parameters.The optimal production process of ionic liquid combined with ultrasonic assisted enzyme extraction was determined by single factor combined response surface experiment.The optimal process for preparing curcumin nanoparticles by ionic crosslinking method was determined by single factor combined response surface experiment with acetic acid concentration,chitosan to sodium tripolyphosphate mass ratio,stirring rate,curcumin mass concentration,sodium tripolyphosphate mass concentration,and chitosan mass concentration as parameters,and drug encapsulation efficiency as response value.Curcumin nanoparticles were prepared under the optimal process,and the particle size,polydispersity index,Zata potential value,drug loading,stability,hemolysis rate,and antioxidant capacity in vivo and in vitro of the nanoparticles were detected.RESULTS AND CONCLUSION:(1)Among the five extraction methods,the curcumin yield of ionic liquid combined with ultrasound-assisted enzyme extraction was the highest,and this method was selected as the curcumin extraction method for subsequent experiments.The results of single factor combined response surface experiment showed that the optimal process for curcumin extraction was:ionic liquid selected 1-hexyl-3-methylimidazolium chloride,reaction temperature 55 ℃,liquid-to-solid ratio 40 mL/g,ultrasound time 57 minutes,ionic liquid concentration 57％,enzyme-drug mass ratio 3.5:10,and the obtained turmeric extraction yield was 3.10％.The optimal preparation process of curcumin nanoparticles was:glacial acetic acid concentration 0.5％,chitosan and sodium tripolyphosphate mass ratio 5.0:1,stirring speed 150 r/min,curcumin mass concentration 2.23 mg/mL,sodium tripolyphosphate mass concentration 1.45 mg/mL,chitosan mass concentration 3.63 mg/mL,and the obtained drug encapsulation efficiency was 90.61％.(2)The drug loading of curcumin nanoparticles was(14.49±0.23)％,the average particle size was(76.95±1.65)nm,the polydispersity coefficient was 0.15±0.02,and the Zata potential value was(32.37±1.46)mV.The curcumin nanoparticles had good stability and blood compatibility,did not induce hemolysis,and had stronger antioxidant capacity in vivo and in vitro than free curcumin.(3)The results show that the process optimization not only solves the problems of low extraction yield,poor solubility,and low bioavailability of curcumin,but also enhances its antioxidant activity in vivo and in vitro.

BACKGROUND:Curcumin is the main active ingredient of turmeric and has significant medicinal value in anti-tumor,anti-inflammatory,antioxidant and other aspects.However,its poor water solubility,unstable chemical properties and easy decomposition lead to difficulty in extracting curcumin and low extraction yield.Therefore,it is particularly important to optimize the curcumin extraction method.OBJECTIVE:To enhance the extraction yield and utilization value of curcumin and optimize the curcumin extraction process and curcumin nanoparticle preparation process.METHODS:Curcumin was extracted from turmeric by ethanol extraction,ultrasonic extraction,ionic liquid extraction,enzyme extraction,and ionic liquid combined with ultrasonic assisted enzyme extraction.The curcumin extraction yield was detected by high performance liquid chromatography;the best extraction method was determined,and subsequent process optimization experiments were carried out.The curcumin extraction yield was the response value with the type of ionic liquid,reaction temperature,ultrasonic time,liquid-to-solid ratio,ionic liquid concentration,and enzyme-drug mass ratio as parameters.The optimal production process of ionic liquid combined with ultrasonic assisted enzyme extraction was determined by single factor combined response surface experiment.The optimal process for preparing curcumin nanoparticles by ionic crosslinking method was determined by single factor combined response surface experiment with acetic acid concentration,chitosan to sodium tripolyphosphate mass ratio,stirring rate,curcumin mass concentration,sodium tripolyphosphate mass concentration,and chitosan mass concentration as parameters,and drug encapsulation efficiency as response value.Curcumin nanoparticles were prepared under the optimal process,and the particle size,polydispersity index,Zata potential value,drug loading,stability,hemolysis rate,and antioxidant capacity in vivo and in vitro of the nanoparticles were detected.RESULTS AND CONCLUSION:(1)Among the five extraction methods,the curcumin yield of ionic liquid combined with ultrasound-assisted enzyme extraction was the highest,and this method was selected as the curcumin extraction method for subsequent experiments.The results of single factor combined response surface experiment showed that the optimal process for curcumin extraction was:ionic liquid selected 1-hexyl-3-methylimidazolium chloride,reaction temperature 55 ℃,liquid-to-solid ratio 40 mL/g,ultrasound time 57 minutes,ionic liquid concentration 57％,enzyme-drug mass ratio 3.5:10,and the obtained turmeric extraction yield was 3.10％.The optimal preparation process of curcumin nanoparticles was:glacial acetic acid concentration 0.5％,chitosan and sodium tripolyphosphate mass ratio 5.0:1,stirring speed 150 r/min,curcumin mass concentration 2.23 mg/mL,sodium tripolyphosphate mass concentration 1.45 mg/mL,chitosan mass concentration 3.63 mg/mL,and the obtained drug encapsulation efficiency was 90.61％.(2)The drug loading of curcumin nanoparticles was(14.49±0.23)％,the average particle size was(76.95±1.65)nm,the polydispersity coefficient was 0.15±0.02,and the Zata potential value was(32.37±1.46)mV.The curcumin nanoparticles had good stability and blood compatibility,did not induce hemolysis,and had stronger antioxidant capacity in vivo and in vitro than free curcumin.(3)The results show that the process optimization not only solves the problems of low extraction yield,poor solubility,and low bioavailability of curcumin,but also enhances its antioxidant activity in vivo and in vitro.

Objective:Primary sclerosing cholangitis (PSC) is a rare autoimmune disease. This study aims to describe the baseline characteristics and clinical outcomes of Chinese PSC patients and explore risk factors associated with prognosis, addressing the lack of long-term prognostic analysis in China.Methods:Clinical data of PSC patients were retrospectively collected from May 2009 to June 2023 in Beijing Friendship Hospital Affiliated to Capital Medical University, and patient follow-up was conducted through outpatient visits, telephone calls, and medical record reviews. The Cox proportional hazards model and the Kaplan-Meier method were employed to identify risk factors and estimate transplant-free survival.Results:A total of 65 PSC patients were enrolled, with male patients accounting for 50.8% and an average age of onset of 44 years. The disease types primarily included large duct PSC (57.9%) and whole duct PSC (22.8%). Most patients (78.5%) sought medical attention due to symptoms, with common clinical manifestations including jaundice (32.3%), fatigue (23.1%), abdominal discomfort (21.5%), pruritus (16.9%), and fever (10.8%). A total of 19 patients (29.2%) had concomitant ulcerative colitis. Compared to large duct PSC or whole duct PSC, small duct PSC showed a lower proportion of concomitant ulcerative colitis ( P<0.001) and milder baseline disease severity. After a median follow-up of 29 months (interquartile range: 11,53), 19 patients experienced liver transplantations and/or liver disease-related deaths. The overall 2-year and 5-year transplant-free survival rates for PSC patients were 76.0% and 59.5%, respectively. Elevated bile acid levels were identified as an independent risk factor for poor outcomes in PSC patients. Conclusion:The study population of Chinese PSC patients predominantly consisted of middle-aged males, characterized by a low ratio of asymptomatic cases, a low incidence of associated inflammatory bowel disease, and a low rate of transplant-free survival. Elevated bile acid level was identified as an independent risk factor for poor outcomes in PSC patients.

A 66-year-old female kidney transplant recipient presented to Shanghai Jiao Tong University Affiliated Renji Hospital on May 24th, 2024 due to recurring intermittent diarrhea for over 16 years. The parasites were found through examination of small intestinal fluid. Small intestinal fluid mNGS combined with blood mNGS confirmed Cyclospora cayetanensis infection. The cause of the diarrhea was clarified. Oral compound sulfamethoxazole was used as treatment, and the patient's diarrhea symptoms improved, and no Cyclospora cayetanensis was found in the small intestinal fluid smear three consecutive times. Parasitic infection factors should be excluded in patients with low immune function and chronic diarrhea. Non-invasive small intestinal fluid smear combined with mNGS detection provides a new method to clarify the cause of chronic diarrhea.

Objective To investigae microbial community structure of lower respiratory tract in severe hospital-acquired pneumonia(SHAP)patients in intensive care unit(ICU)using metagenomic next-generation sequencing(mNGS).Methods mNGS was performed on bronchoalveolar lavage fluid(BALF)of 84 patients with SHAP.Patients were grouped based on age,smoking status,underlying diseases and duration of artificial airway.The differences in α diversity,β diversity,microbial composition and community structure of airway microbiota were compared between different groups.The differential airway microbiota associated with artificial airway were screened,and microbial co-occurrence networks was constructed to observe the interaction in microorganisms.Results Results of α diversity analysis revealed that diversity and evenness of the microbial community were higher in young adults compared to those of middle-aged patients,while microbial diversity and evenness were significantly reduced in patients with comorbid stroke.In the group of artificial airway treatment,the diversity and uniformity of microorganisms decreased as the duration of artificial airway treatment increased.The diversity was the lowest when the artificial airway treatment lasted for more than 3 days.β diversity analysis confirmed that there were significant differences in the distinct microbial community structures between the>3 days support group and the non-intubated and≤3 days support cohorts.Acinetobacter baumannii was dominant in all groups.The bacterial diversity was significantly higher in the middle-aged group,the non-smoking group,the group without artificial airway therapy,the group without diabetes mellitus,the group with artificial airway therapy≥3 days and the group with chronic lung disease than those of other groups.In particular,pseudomonas aeruginosa,corynebacterium striatum and veillonella parvula were enriched in these groups.Difference analysis showed that there were significant differences in pseudomonas aeruginosa and corynebacterium striatum between the group with artificial airway treatment>3 days,the group without artificial airway therapy and the group with artificial airway treatment≤3 days.Network co-occurrence showed that there may be synergistic or antagonistic relationships between some microorganisms.Conclusion The microbial diversity of the lower respiratory tract in patients with SHAP significantly decreases in the elderly,those with concurrent stroke and those receiving artificial airway treatment.For these groups,rational use of antibiotics should be adopted to guide precise anti-infection treatment.

Objective:To investigate the biological role and molecular mechanism of checkpoint kinase 1 (CHK1) in delaying cardiac aging in mice.Methods:In vitro, a senescence model of H9C2 cells (a cardiomyocyte line) was induced using H 2O 2. A control group (without H 2O 2 treatment) and three H 2O 2-treated groups (at concentrations of 10, 30, and 50 μmol/L) were set up. The CCK-8 assay was used to evaluate the proliferative activity of cells in each group; Western blot analysis was employed to detect the expression level of CHK1; and quantitative real-time polymerase chain reaction (qRT-PCR) was utilized to determine the messenger RNA (mRNA) expression levels of P16 and interleukin-1β (IL-1β). In vivo, C57BL/6 wild-type mice aged 2 months ( n=15) and 24 months ( n=40), as well as myocardial-specific CHK1-overexpressing (CHK1-TG) mice aged 2 months ( n=15) and 24 months ( n=40), were selected. The mice were divided into four groups based on age and genotype: 2-month-old wild-type (WT-2M), 24-month-old wild-type (WT-24M), 2-month-old CHK1-TG (CHK1-TG-2M), and 24-month-old CHK1-TG (CHK1-TG-24M). Echocardiography was used to evaluate cardiac function of mice in the WT-24M and CHK1-TG-24M groups. Western blot analysis was conducted to measure the protein expression levels of CHK1, total Ras-related protein 1 (Rap1), NADPH oxidase 4 (Nox4), and Rap1-guanosine triphosphate (Rap1-GTP, the active form of Rap1) in the cardiac tissue of mice in each group. qRT-PCR was used to detect the messenger RNA (mRNA) expression levels of CHK1, collagen type Ⅰ (Coll1), matrix metalloproteinase-2 (Mmp2), alpha-smooth muscle actin (α-SMA), P53, P21, P16, thioredoxin 1 (Trx1), thioredoxin reductase (TrxR), glutathione recluctase (GR), Rap1, and Nox4. Immunofluorescence staining was employed to determine the protein expression levels of P53, P21, and P16, as well as the proportion of histone H2AX phosphorylation-positive cells. Dihydroethidium (DHE) staining was used to detect the relative intensity of DHE. Wheat germ agglutinin staining, HE staining, Masson staining and Sirius red staining were applied to measure the cross-sectional area of cardiomyocytes, cardiac morphology, and myocardial fibrosis area. Mice in the WT-24M and CHK1-TG-24M groups were intraperitoneally injected with the Rap1 activity inhibitor GGTI298 (25 μmol/kg). After injection, the oxidative stress damage in the cardiac tissue of the mice was detected, along with the mRNA expression levels of fibrosis-related indicators (Coll1, Mmp2, and α-SMA) and cell cycle inhibitory proteins (P16, P21, and P53). Results:A concentration of 30 μmol/L was determined as the optimal concentration for establishing an H 2O 2-induced senescence model of myocardial cells in vitro. The expression level of CHK1 in H9C2 cells of the 30 μmol/L H 2O 2 group was lower than that in the control group ( P<0.05). Echocardiographic examination showed that the left ventricular ejection fraction ((61.08±1.13)% vs. (52.55±2.02)%) and fractional shortening ((31.80±1.27)% vs. (25.18±1.59)%) of mice in the CHK1-TG-24M group were higher than those in the WT-24M group (both P<0.05). qRT-PCR and Western blot analysis revealed that, compared with the WT-24M group, mice in CHK1-TG-24M group had higher expression levels of CHK1 and its mRNA, lower expression levels of Nox4 and its mRNA, and higher expression level of Rap1-guanosine triphosphate (Rap1-GTP) (all P<0.05). However, there were no statistically significant differences in the total expression level of Rap1 and its mRNA between the two groups (both P>0.05). In addition, the mRNA expression levels of Coll1, Mmp2, and α-SMA in myocardial tissue of mice in the CHK1-TG-24M group were lower than those in the WT-24M group (all P<0.05). Immunofluorescence staining results showed that the expression levels of P53, P21, and P16 proteins, as well as the proportion of phosphorylated histone H2AX-positive cells in myocardial tissue of mice in the WT-24M group were higher than those in the CHK1-TG-24M group (all P<0.05). qRT-PCR further confirmed that the mRNA expression levels of the above-mentioned proteins in cardiac tissue of mice in the WT-24M group were higher than those in the CHK1-TG-24M group (all P<0.05). DHE staining results indicated that the relative intensity of DHE in cardiac tissue of mice in the CHK1-TG-24M group was lower than that in the WT-24M group ( P<0.05). Meanwhile, the left ventricular internal diameter, cross-sectional area of cardiomyocytes, and myocardial fibrosis area of mice in the CHK1-TG-24M group were all smaller than those in the WT-24M group (all P<0.05). Furthermore, the degree of DNA damage in cardiac tissue as well as the mRNA levels of fibrosis-related indicators (Coll1, Mmp2, and α-SMA) and cell cycle inhibitory proteins (P53, P21, P16) in mice of the WT-24M+GGTI298 group were higher than those in the WT-24M group and the CHK1-TG-24M+GGTI298 group (all P<0.05). Conclusion:CHK1 alleviates oxidative stress-induced damage in mouse cardiomyocytes by activating the Rap1/Nox4 signaling pathway, thereby delaying cardiac aging in mice.

Objective To investigae microbial community structure of lower respiratory tract in severe hospital-acquired pneumonia(SHAP)patients in intensive care unit(ICU)using metagenomic next-generation sequencing(mNGS).Methods mNGS was performed on bronchoalveolar lavage fluid(BALF)of 84 patients with SHAP.Patients were grouped based on age,smoking status,underlying diseases and duration of artificial airway.The differences in α diversity,β diversity,microbial composition and community structure of airway microbiota were compared between different groups.The differential airway microbiota associated with artificial airway were screened,and microbial co-occurrence networks was constructed to observe the interaction in microorganisms.Results Results of α diversity analysis revealed that diversity and evenness of the microbial community were higher in young adults compared to those of middle-aged patients,while microbial diversity and evenness were significantly reduced in patients with comorbid stroke.In the group of artificial airway treatment,the diversity and uniformity of microorganisms decreased as the duration of artificial airway treatment increased.The diversity was the lowest when the artificial airway treatment lasted for more than 3 days.β diversity analysis confirmed that there were significant differences in the distinct microbial community structures between the>3 days support group and the non-intubated and≤3 days support cohorts.Acinetobacter baumannii was dominant in all groups.The bacterial diversity was significantly higher in the middle-aged group,the non-smoking group,the group without artificial airway therapy,the group without diabetes mellitus,the group with artificial airway therapy≥3 days and the group with chronic lung disease than those of other groups.In particular,pseudomonas aeruginosa,corynebacterium striatum and veillonella parvula were enriched in these groups.Difference analysis showed that there were significant differences in pseudomonas aeruginosa and corynebacterium striatum between the group with artificial airway treatment>3 days,the group without artificial airway therapy and the group with artificial airway treatment≤3 days.Network co-occurrence showed that there may be synergistic or antagonistic relationships between some microorganisms.Conclusion The microbial diversity of the lower respiratory tract in patients with SHAP significantly decreases in the elderly,those with concurrent stroke and those receiving artificial airway treatment.For these groups,rational use of antibiotics should be adopted to guide precise anti-infection treatment.

Objective This study aimed to examine the risk factors and prognostic factors of brucellar spondylitis for early prevention and treatment of the disease,and improving the outcomes of patients.Methods A retrospective case-control study was conducted on the patients with brucellosis who were hospitalized in the Third Hospital of Hebei Medical University from June 2020 to June 2022.Patients were assigned to brucellosis without spondylitis group or brucellar spondylitis group according to the presence of spondylitis.The patients in brucellar spondylitis group were followed for 1 year.Then they were stratified into a subgroup of good or poor prognosis according to clinical outcomes.The dataset for the demographic and clinical variables of patients were analyzed using SPSS 26.0 software.Results A total of 300 patients with brucellosis were enrolled,including 113 cases of brucellosis without spondylitis and 187 cases of brucellar spondylitis.Multivariate analysis showed that age,time from onset to diagnosis,low back pain,and erythrocyte sedimentation rate were independent risk factors for brucellar spondylitis(P＜0.05).Of the 154 cases of brucellar spondylitis with known outcomes,121 cases showed good prognosis and 33 cases had poor prognosis.COX regression analysis showed that the time from onset to diagnosis,diabetes mellitus,paravertebral abscess,and neurological impairment were independent risk factors for poor prognosis in patients with brucellar spondylitis(P＜0.05).Conclusions Old age,prolonged time from onset to diagnosis,low back pain,and increased erythrocyte sedimentation rate are independent risk factors for spondylitis in patients with brucellosis.Prolonged time from onset to diagnosis,diabetes mellitus,paravertebral abscess,and neurological impairment are independent risk factors for poor prognosis of brucellar spondylitis.

Objective:To investigate the effect of DEAD-box helicase (DDX) 21 on myocardial ischemia-reperfusion (I/R) injury and its potential mechanisms.Methods:In vivo, adult male Bama pigs and C57BL/6J mice were used to establish a myocardial I/R injury model by ligating the left anterior descending coronary artery, with sham-operated groups set as controls. The expression of DDX21 in myocardium after I/R injury was assessed by quantitative real-time PCR (qRT-PCR), Western blot, and immunofluorescence staining. Following the establishment of the myocardial I/R injury model in mice, AAV9 vectors with cardiac-specific expression were injected in situ into the peri-infarct region (The I/R+DDX21 group, I/R+negative control (NC) group, I/R+sh-NC group and I/R+sh-DDX21 group were injected with AAV9:cTnT-DDX21, AAV9:cTnT-NC, AAV9:cTnT-sh-NC and AAV9:cTnT-sh-DDX21, respectively). Additionally, the I/R+A-485 group received intraperitoneal injections of the cAMP response element-binding protein (CREB) binding protein inhibitor A-485, while the I/R+PBS group was injected with an equivalent volume of phosphate-buffered saline (PBS) as the control. Echocardiography was performed on postoperative days 1 and 28 to evaluate cardiac function (left ventricular ejection fraction and fractional shortening). At 28 days post-surgery, mice were euthanized and heart tissues were harvested for histological sectioning. Myocardial fibrosis was evaluated using Masson′s trichrome staining. In vitro, primary cardiomyocytes were isolated from neonatal day 1 C57BL/6J mice using enzymatic digestion method. Cardiomyocytes were transfected with plasmids or small interfering RNA (siRNA). The cardiomyocytes transfected with DDX21-siRNA were assigned to the siDDX21 group, those transfected with the DDX21 plasmid were assigned to the DDX21 group, and those transfected with the corresponding empty plasmid or siRNA were assigned to the NC group. Additionally, cardiomyocytes were treated with A-485 (A-485 group) or PBS (PBS group). An oxygen-glucose deprivation/reoxygenation (OGD/R) model was used to simulate cellular injury. Transcriptome sequencing was performed to identify downstream mechanisms of DDX21. Differential gene expression analysis was conducted using software such as DESeq2, and alternative splicing events in the mRNA transcriptome were analyzed using rMATS software. Mitochondrial superoxide, mitochondrial membrane potential, ATP content, and mitochondrial respiratory chain complex enzyme activity in cardiomyocytes were detected using immunofluorescence staining and commercial assay kits. The oxidative phosphorylation level of the cells was assessed by the Seahorse extracellular flux analyzer. Acetylated DDX21 levels were measured using co-immunoprecipitation and Western blot assays.Results:The expression levels of DDX21 in myocardium from the Bama pigs and mice in the I/R injury model were significantly higher than those in the sham group (all P<0.001). Echocardiographic results showed that at 28 days post-surgery, compared to the I/R+NC group, the I/R+DDX21 group exhibited higher left ventricular ejection fraction and fractional shortening, while the I/R+sh-DDX21 group showed lower values; Masson staining results demonstrated that, compared to the I/R+NC group, the myocardial fibrosis area in the I/R+DDX21 group was significantly reduced, whereas it was significantly increased in the I/R+sh-DDX21 group (all P<0.001). Transcriptomic sequencing results suggested that DDX21 may influence myocardial injury by regulating mitochondrial metabolic activity. In vitro, compared to the OGD/R+NC group, the OGD/R+DDX21 group exhibited lower mitochondrial superoxide levels, higher polymer/monomer ratio, maximal oxygen consumption, reserve capacity, and ATP content. In contrast, the OGD/R+siDDX21 group showed the opposite results, with reduced activity of mitochondrial respiratory chain complex V (all P<0.05). Mechanistically, rMATS software and other analyses indicated that knockdown of DDX21 affected the alternative 3′ splicing sites of ATP5J precursor mRNA, inhibiting the splicing of certain exonic sequences. Overexpression of DDX21 upregulated both mRNA and protein levels of ATP5J. Co-immunoprecipitation experiments showed that, compared to the PBS group, acetylated DDX21 levels were reduced in the A-485 group. Further in vivo experiments showed that, compared to the I/R+PBS group, the I/R+A-485 group exhibited higher left ventricular ejection fraction and fractional shortening, and a lower proportion of left ventricular fibrosis (all P<0.001). Conclusions:DDX21 improves cardiomyocyte energy metabolism and alleviates I/R injury by regulating the alternative splicing of ATP5J. A-485 holds potential as a novel small molecule candidate for the treatment of myocardial injury.

Objective:To investigate the biological role and molecular mechanism of checkpoint kinase 1 (CHK1) in delaying cardiac aging in mice.Methods:In vitro, a senescence model of H9C2 cells (a cardiomyocyte line) was induced using H 2O 2. A control group (without H 2O 2 treatment) and three H 2O 2-treated groups (at concentrations of 10, 30, and 50 μmol/L) were set up. The CCK-8 assay was used to evaluate the proliferative activity of cells in each group; Western blot analysis was employed to detect the expression level of CHK1; and quantitative real-time polymerase chain reaction (qRT-PCR) was utilized to determine the messenger RNA (mRNA) expression levels of P16 and interleukin-1β (IL-1β). In vivo, C57BL/6 wild-type mice aged 2 months ( n=15) and 24 months ( n=40), as well as myocardial-specific CHK1-overexpressing (CHK1-TG) mice aged 2 months ( n=15) and 24 months ( n=40), were selected. The mice were divided into four groups based on age and genotype: 2-month-old wild-type (WT-2M), 24-month-old wild-type (WT-24M), 2-month-old CHK1-TG (CHK1-TG-2M), and 24-month-old CHK1-TG (CHK1-TG-24M). Echocardiography was used to evaluate cardiac function of mice in the WT-24M and CHK1-TG-24M groups. Western blot analysis was conducted to measure the protein expression levels of CHK1, total Ras-related protein 1 (Rap1), NADPH oxidase 4 (Nox4), and Rap1-guanosine triphosphate (Rap1-GTP, the active form of Rap1) in the cardiac tissue of mice in each group. qRT-PCR was used to detect the messenger RNA (mRNA) expression levels of CHK1, collagen type Ⅰ (Coll1), matrix metalloproteinase-2 (Mmp2), alpha-smooth muscle actin (α-SMA), P53, P21, P16, thioredoxin 1 (Trx1), thioredoxin reductase (TrxR), glutathione recluctase (GR), Rap1, and Nox4. Immunofluorescence staining was employed to determine the protein expression levels of P53, P21, and P16, as well as the proportion of histone H2AX phosphorylation-positive cells. Dihydroethidium (DHE) staining was used to detect the relative intensity of DHE. Wheat germ agglutinin staining, HE staining, Masson staining and Sirius red staining were applied to measure the cross-sectional area of cardiomyocytes, cardiac morphology, and myocardial fibrosis area. Mice in the WT-24M and CHK1-TG-24M groups were intraperitoneally injected with the Rap1 activity inhibitor GGTI298 (25 μmol/kg). After injection, the oxidative stress damage in the cardiac tissue of the mice was detected, along with the mRNA expression levels of fibrosis-related indicators (Coll1, Mmp2, and α-SMA) and cell cycle inhibitory proteins (P16, P21, and P53). Results:A concentration of 30 μmol/L was determined as the optimal concentration for establishing an H 2O 2-induced senescence model of myocardial cells in vitro. The expression level of CHK1 in H9C2 cells of the 30 μmol/L H 2O 2 group was lower than that in the control group ( P<0.05). Echocardiographic examination showed that the left ventricular ejection fraction ((61.08±1.13)% vs. (52.55±2.02)%) and fractional shortening ((31.80±1.27)% vs. (25.18±1.59)%) of mice in the CHK1-TG-24M group were higher than those in the WT-24M group (both P<0.05). qRT-PCR and Western blot analysis revealed that, compared with the WT-24M group, mice in CHK1-TG-24M group had higher expression levels of CHK1 and its mRNA, lower expression levels of Nox4 and its mRNA, and higher expression level of Rap1-guanosine triphosphate (Rap1-GTP) (all P<0.05). However, there were no statistically significant differences in the total expression level of Rap1 and its mRNA between the two groups (both P>0.05). In addition, the mRNA expression levels of Coll1, Mmp2, and α-SMA in myocardial tissue of mice in the CHK1-TG-24M group were lower than those in the WT-24M group (all P<0.05). Immunofluorescence staining results showed that the expression levels of P53, P21, and P16 proteins, as well as the proportion of phosphorylated histone H2AX-positive cells in myocardial tissue of mice in the WT-24M group were higher than those in the CHK1-TG-24M group (all P<0.05). qRT-PCR further confirmed that the mRNA expression levels of the above-mentioned proteins in cardiac tissue of mice in the WT-24M group were higher than those in the CHK1-TG-24M group (all P<0.05). DHE staining results indicated that the relative intensity of DHE in cardiac tissue of mice in the CHK1-TG-24M group was lower than that in the WT-24M group ( P<0.05). Meanwhile, the left ventricular internal diameter, cross-sectional area of cardiomyocytes, and myocardial fibrosis area of mice in the CHK1-TG-24M group were all smaller than those in the WT-24M group (all P<0.05). Furthermore, the degree of DNA damage in cardiac tissue as well as the mRNA levels of fibrosis-related indicators (Coll1, Mmp2, and α-SMA) and cell cycle inhibitory proteins (P53, P21, P16) in mice of the WT-24M+GGTI298 group were higher than those in the WT-24M group and the CHK1-TG-24M+GGTI298 group (all P<0.05). Conclusion:CHK1 alleviates oxidative stress-induced damage in mouse cardiomyocytes by activating the Rap1/Nox4 signaling pathway, thereby delaying cardiac aging in mice.