The role of short-chain fatty acids in Clostridioides difficile infection: A review.

Clostridioides difficile is a Gram-positive, obligate anaerobic, spore-producing intestinal opportunistic pathogen. CDI outbreaks in Europe and the Americas in recent years are a major health concern. Intestinal short-chain fatty acids (SCFAs) are an important energy source for colonic epithelial cells, and the roles of SCFAs in reducing intestinal inflammation, inhibiting intestinal tumors, and regulating gut microbial homeostasis are being actively researched. Furthermore, SCFAs attenuate CDI or directly inhibit C. difficile growth through different pathways in vivo and in vitro. This review assesses the role of SCFAs in CDI and discusses the potential use of these molecules as therapeutic targets for CDI.

Carriage of Clostridioides difficile in healthy infants in the community of Handan, China: A 1-year follow-up study.

OBJECTIVE: Clostridioides difficile may colonize healthy infants and young children asymptomatically and for the long-term. C. difficile genotypes and the rate and determinants of colonization differ substantially and vary among countries and regions. A 1-year follow-up study was performed to determine the incidence, kinetics and influencing factors of C. difficile intestinal colonization. METHODS: Twenty-nine healthy infants (14 girls and 15 boys) living at home with their parents in Handan City were followed by survey from birth to 1 year of age, specifically from October 2014 through December 2015. C. difficile isolates were typed by PCR ribotyping and analyzed for the presence of toxin genes. RESULTS: During the follow-up study period in the first year of life, 20 of the 29 total enrolled infants acquired C. difficile. A total of 437 fecal samples were obtained, and 111 (25.4%) samples contained C. difficile, including 79 (71.2%) toxigenic strains. The toxigenic isolates comprised six PCR ribotypes, and two PCR ribotypes were identified as nontoxigenic strains. CONCLUSION: Our study showed that C. difficile colonization increase with age during the 12-month period, and the dominant toxigenic types of C. difficile isolates in infants were those involved in long-term colonization. Feeding patterns may affect the dynamic progress of C. difficile colonization.

Epidemiological investigation of Clostridioides difficile colonization in Chinese community infants.

Clostridioides difficile is a colonizer of the human gut; asymptomatic colonization has been reported to be more common in infants and is highly variable across regions even with no symptoms of diarrhea or death. Antibiotic treatment strategies might increase the antibiotic resistance of C. difficile. We performed a one-point study involving 1098 healthy infants (0-36 months) to address the deficiency of reports on C. difficile colonization in Chinese community infants. The C. difficile colonization rate was 22.8% (250/1098), and more than half of the strains (55.2%) were toxigenic isolates. Among the 138 toxigenic isolates, 111 were of the A+B+CDT- genotype, 26 strains were A-B+CDT-, and one strain was A+B+CDT+. Fifteen different PCR ribotypes were found among the 250 isolates, and PCR-ribotype HB03 appeared to be dominant type, accounting for 19.6% (49/250). High levels of resistance to antimicrobial agents were observed. Our study showed that age and hospitalization before stool collection were positively correlated with the C. difficile colonization rate, whereas the delivery term was negatively related to the colonization rate. Particular attention should be paid to the increasing resistance of C. difficile to rifamycin.

[Analysis of resistance tendency of bloodstream-infecting pathogens in China].

OBJECTIVE: To investigate the resistance profiles and the trend of bloodstream-infecting pathogens isolated from hospitalized patients during 2004-2010. METHODS: The bloodstream isolates were collected from 18 hospitals in 17 cities. Minimum inhibition concentrations (MIC) were determined using the agar dilution method recommended by CLSI (Clinical and Laboratory Standards Institute), and susceptibility results were analyzed according to the 2011 CLSI guideline. RESULTS: Among the 2004-2005, 2007-2008 and 2009-2010 periods, the proportions of clinical isolates were similar; 43.1% (149 isolates), 34.0% (151 isolates) and 47.5% (776 isolates) for Gram positive strains, 56.9% (197 isolates), 66.0% (293 isolates) and 52.5% (858 isolates) for Gram negative strains, respectively. The isolating rate of MRSA was 54.1% (20/37) in 2007-2008, which was the highest among the 3 periods during 2004 to 2010, while it decreased in 2009-2010 (36.5%, 62/170). The MRCNS proportions were similar across the 3 periods. One (1.8%) vancomycin-resistant Enterococcus faecium and 1 linezolid-resistant Enterococcus faecalis were found. Although the isolating rates of penicillin non-sensitive strains (oral) were similar between 2009-2010 and 2007-2008 [54.5% (6/11) and 53.9% (7/13), respectively], the resistant rates increased from 0% in 2007-2008 to 30.8% (4/13) in 2009-2010. The results were similar according to the non-meningitis criterion (IV), and the susceptibility rates decreased from 100.0% (11 isolates) in 2007-2008 to 84.6% (11/13) in 2009-2010. ESBL-harboring strains in E. coli were similar among the 3 periods during 2004 to 2010 [66.7% (30/45), 73.2% (71/97) and 67.9% (233/343), respectively]. ESBL-producing strains in Klebsilla pnuemoniae decreased year after year, 72.4% (21/29), 50.0% (18/36) and 41.1% (65/158) in 2004-2005, 2007-2008 and 2009-2010, respectively. Except that the sensitive rate of Enterobacter cloacae to ertapenem was 80% (32/40), the sensitive rates of other strains to carbapenems were still above 90% and the resistance rates were less than 5%. Acinetobacter baumannii had the highest multi-drug resistance rate (81.8%, 81/99). One strain (1.0%, 1/99) of Acinetobacter baumannii isolated in 2009-2010 was reported to be pan-resistant. CONCLUSIONS: We are facing a more serious situation of bacterial resistance. Acinetobacter baumannii resistance was most serious, usually with the characteristics of multiple drug resistance, and even pan-resistance. Carbapenems remain to be the most effective against enterobacteriaceae. Strains resistant to novel antibiotics (linezolid and tigecycline) have emerged.

Mental health and psychosocial problems among laboratory technicians in response to the COVID-19 pandemic in Hebei, China.

Objective: During the coronavirus disease 2019 (COVID-19) pandemic, an increased mental burden has been widely reported among medical health workers such as physicians and nurses. However, data on laboratory technicians exposed to COVID-19 have rarely been published. The aim of this study was to assess the magnitude of psychological symptoms among laboratory technicians and analyze potential risk factors associated with these symptoms. Methods: A cross-sectional online survey was performed via the Wenjuanxing platform (a professional online questionnaire platform) (https://www.wjx.cn/mobile/statnew.aspx) to investigate the mental health of laboratory technicians during the COVID-19 pandemic in Hebei, China from October 4, 2021, to November 3, 2021. The online questionnaire included demographic and occupational characteristics data of responders, and the Symptom Check List-90-Revised (SCL90-R)was used to quantify the magnitude of psychological symptoms among laboratory technicians. Participants' demographic and occupational characteristics were analyzed using descriptive statistical analyses. Chi-square tests were applied to compare the severity of each symptom between two or more groups. A binary logistic regression model was developed to identify the predictors of laboratory technicians' mental health in response to the COVID-19 pandemic, and outcomes are presented as odds ratios and 95% confidence interval. Statistical analysis was performed using SPSS version 21 (SPSS, New Orchard Road, Armonk, New York, USA). Results: A total of 3081 valid questionnaires were collected. Of these 3081 participants, 338 (11.0%) reported a total SCL90-R score >160, which indicated positive psychological symptoms. Among the 338 participants who reported psychological problems, most of them were mild symptoms. Several factors associated with mental health problems in laboratory technicians during COVID-19 were found, which include a history of physical and/or psychological problems (all 10 symptoms p < 0.001), more than 10 years of work experience (depression symptoms: OR = 2.350, p = 0.024; anxiety symptoms: OR = 2.642, p = 0.038), frontline work (depression symptoms: OR = 1.761, p = 0.001; anxiety symptoms: OR = 2.619, p < 0.001; hostility symptoms: OR = 1.913, p = 0.001), participant in more than 3 times large-scale SARS-CoV-2 screenings and more than 36 h per week in SARS-CoV-2 nucleic acid testing. Conclusion: A portion of laboratory technicians reported experiencing varying levels of psychological burden. During the COVID-19 pandemic, multiple interventions should be developed and implemented to address existing psychosocial challenges and promote the mental health of laboratory technicians.

Prevalence and molecular characterization of Clostridioides difficile infection in China over the past 5 years: a systematic review and meta-analysis.

OBJECTIVES: The aim of this study was to provide an overview of the prevalence and molecular characteristics of Clostridioides difficile infection (CDI) in China in the past 5 years. METHODS: A systematic literature review was conducted according to the preferred reporting items for systematic reviews and meta-analyses guidelines. Nine databases were searched for relevant studies published between January 2017 and February 2022. The Joanna Briggs Institute critical appraisal tool was used to assess the quality of included studies, and R software version 4.1.3 was used for data analysis. Funnel plots and Egger regression tests were also performed to assess publication bias. RESULTS: A total of 50 studies were included in the analysis. The pooled prevalence of CDI in China was 11.4% (2696/26,852). The main circulating C. difficile strains in southern China were ST54, ST3, and ST37, consistent with the overall situation in China. However, the most prevalent genotype in northern China was ST2, which was previously underappreciated. CONCLUSION: Based on our findings, increased awareness and management of CDI is necessary to reduce the prevalence of CDI in China.

The value of fecal calprotectin in Clostridioides difficile infection: A systematic review.

As a marker of inflammation, calprotectin has potential application value in a variety of inflammatory diseases, such as arthritis and bacterial infections. Clostridioides difficile infection (CDI) is an infectious disease that causes intestinal damage and inflammation. This systematic review aims to determine whether fecal calprotectin has application value in CDI. Nine databases were searched from inception to 6 June 2022, and 17 studies were included. These studies were divided into four groups according to their content. Generally speaking, fecal calprotectin is not an ideal indicator for the diagnosis and prognosis prediction of CDI but may serve as a potential indicator for assessing disease severity and as a readily detectable marker for CDI screening. In addition, patients in need of treatment or with detectable toxins in stool may tend to have higher levels of fecal calprotectin. In summary, fecal calprotectin has some potential application value in CDI. However, further studies are needed to verify these findings and determine the reliability of calprotectin as a biomarker for CDI.

Optimization of separation of heavy metals by capillary electrophoresis with contactless conductivity detection.

The separation of four toxic metal ions (Cr(3+) , Pb(2+) , Hg(2+) , Ni(2+) ) was achieved by optimizing the composition of the histidine/tartaric acid background electrolyte. An on-column preconcentration technique, viz. field amplified sample injection, was performed to improve the sensitivity. This method afforded an enhancement factor of up to 91,800 fold with the LODs ranging from 0.005 to 2.32 µg/L, which were well below the maximum contaminant levels set by the United States Environmental Protection Agency. The robustness of this method was demonstrated with its application to the analysis of real samples including tap water, drain water, and reservoir water with recoveries between 90 and 120%.

Molecular evolution of influenza B virus during 2011-2017 in Chaoyang, Beijing, suggesting the free influenza vaccine policy.

Two influenza B virus lineages, B/Victoria and B/Yamagata, are co-circulating in human population. While the two lineages are serologically distinct and TIV only contain one lineage. It is important to investigate the epidemiological and evolutionary dynamics of two influenza B virus lineages in Beijing after the free influenza vaccine policy from 2007. Here, we collected the nasopharyngeal swabs of 12657 outpatients of influenza-like illness and subtyped by real-time RT-PCR during 2011-2017. The HA and NA genes of influenza B were fully sequenced. The prevalence is the highest in the 6-17 years old group among people infected with influenza B. Yamagata-lineage virus evolved to two inter-clade from 2011-2014 to 2014-2017. The amino acids substitutions of HA1 region were R279K in strains of 2011-2014 and L173Q, M252V in strains of 2014-2017. Substitutions L58P, I146V were observed in HA1 region of Victoria-lineage virus in 2011-2012 and I117V, N129D were showed in 2015-2017. Phylogenetic analysis of NA showed Yamagata-Victoria inter-lineage reassortant occurred in 2013-2014. Influenza B mainly infect the school-aged children in Beijing and the free influenza vaccine inoculation does not seem to block school-age children from infection with influenza B. The antigen characteristics of circulating influenza B were different to the recommended vaccine strains. We concluded that the Victoria-lineage vaccine strain should been changed and the free influenza vaccine should be revalued.

[The characteristics of biofilm formation in endotracheal tubes in ventilated patients].

OBJECTIVE: To evaluate the etiology and drug resistance of biofilms in endotracheal tubes in respiratory intensive care unit (RICU). METHODS: A prospective cohort study was conducted. The biofilms were observed by scanning electron microscopy at different times of ventilation. The pathogens were identified and their resistance to antibiotics were analyzed. RESULTS: Twenty one VAP cases were identified in 39 mechanically ventilated patients (53.85%). Patchy biofilms were observed 2 d to 7 d after the initiation of ventilation. After 7 d to 10 d, 87.5% of the endotracheal tubes were covered by biofilms. Biofilms were identified in all the tubes longer than 10 d. CONCLUSIONS: The incidence of VAP increased with prolonged mechanical ventilation. Meanwhile the antibiotic resistance rate increased and more pathogens isolated were consistent with those in the biofilms.

The putative compatible solute-binding protein ProX from Mycobacterium tuberculosis H37Rv: biochemical characterization and crystallographic data.

In Mycobacterium tuberculosis, the proX gene encodes a putative compatible solute-binding protein (MtProX). However, it was found through sequence alignment that the MtProX protein has very different ligand-binding residues compared with other compatible solute-binding proteins, implying that MtProX may bind to ligands that are as yet uncharacterized. In this work, it was demonstrated that MtProX binds to polyphenols such as phloretin, monoacetylphloroglucinol and 2,4-dihydroxyacetophloroglucinol with dissociation constants between 20 and 70 µM. Crystals of MtProX were obtained using a precipitant consisting of 0.2 M NaCl, 0.1 M Tris pH 8.5, 25%(w/v) polyethylene glycol 3350. The crystals diffracted to 2.10 Šresolution and belonged to space group P43212, with unit-cell parameters a = b = 90.17, c = 161.92 Å, α = ß = Î³ = 90.0°. Assuming the presence of two MtProX molecules in the asymmetric unit, the Matthews coefficient was calculated to be 2.74 Å3 Da-1, which corresponds to a solvent content of 55%.

Expression of soluble programmed death-1 protein in peripheral blood regulatory T cells and its effects on rheumatoid arthritis progression.

The present study aimed to investigate the role of the soluble programmed death­1 (sPD-1) protein, which is released by peripheral blood regulatory T cells (Treg) during the progression of rheumatoid arthritis (RA). From October 2012 to May 2014, 82 RA patients (RA group) and 90 healthy volunteers (healthy controls; HC) were recruited. Cluster of differentiation (CD)4, CD25 and forkhead/winged helix transcription factor p3 (Foxp3) and expression of cytotoxic T lymphocyte associated antigen 4 (CTLA-4) and Foxp3 were detected by flow cytometry. Expression of sPD­1 in Treg was detected by western blot analysis. Immunosuppressive activity of CD4+CD25­ Treg was measured via thiazolyl blue in an MTT assay. ELISA was used to detect interleukin­10 (IL­10), transforming growth factor beta (TGF-ß), interleukin-4 (IL-4), interferon­Î³ (IFN-γ) and nuclear factor of activated T cells (NF­AT). It was observed that in peripheral blood, CD4+CD25-FOXP3+/CD4+ levels were reduced in the RA group (P<0.001), and sPD­1 levels were markedly higher (P<0.001), compared with the HC group. Additionally, it was observed that relative sPD­1 protein expression in the small interfering RNA (siRNA)-sPD-1 treated group was reduced compared with the untreated and scrambled siRNA groups (all P<0.0001). The mean fluorescence intensity of CTLA-4 and Foxp3 decreased markedly upon transfection with siRNA-sPD-1 (P<0.001). Compared with the normal CD4+CD25­ T group, optical density (OD)540 values, IFN-γ/IL-4 concentration ratio and NF­AT activity in siRNA untreated and scramble groups reduced significantly (all P<0.001). OD540 value, IFN-γ/IL-4 concentration ratio and NF­AT activity in the siRNA­sPD­1 group were significantly upregulated (all P<0.001). Therefore, sPD-1 may suppress the level of CD4+CD25­ Tregs in the peripheral blood of RA patients, and may be involved in a variety of immune processes mediated by CD4+CD25­ Tregs.

Oral administration of soy-derived genistin suppresses lipopolysaccharide-induced acute liver inflammation but does not induce thymic atrophy in the rat.

Genistein, the principal isoflavone present in soy, has been identified as a protein tyrosine kinase (PTK) inhibitor that has in vitro anti-inflammatory effects. Whether genistein has in vivo anti-inflammatory effects remains unknown yet. Injecting or feeding rats with the unconjugated form of genistein (aglycone) results in decreased thymic weight and lymphocytopenia. However, 95-99% of genistein is present as the conjugated form genistin (genistein glycoside) in soy or soy-derived products. This study was undertaken to reveal whether genistin, as well as genistein, has anti-inflammatory effects in vivo. After oral administration of equimolar genistein (namely 7.4 or 74 micromol/dose) at daily doses of 2.0 or 20 mg/kg, or genistin at daily doses of 3.2 or 32 mg/kg for 3 days to male rats, both aglycone and glycoside suppressed the production of lipopolysaccharide (LPS)-induced tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta, and IL-6 in both from the liver and in the sera. Aglycone induced thymic atrophy while glycoside did not. In vitro preincubation of liver slices from naïve rat with genistein aglycone or glycoside suppressed LPS-induced TNF-alpha production in a dose-dependent manner. Taken together, both in vivo and in vitro administration of genistin and genistein suppressed LPS-induced liver pro-inflammatory cytokine production. However, equimolar oral administration of genistin did not induce thymus atrophy. Further investigation in long-term isoflavone intake is required especially among neonates. The results suggest that the safety evaluation of the consumption of isoflavone should be based on isoflavone glycoside but not aglycone.

Dioxin concentration in human milk in Hebei province in China and Tokyo, Japan: potential dietary risk factors and determination of possible sources.

Very limited information is available on body burdens and environmental levels of dioxins and dioxin-like PCBs (dl-PCBs) in mainland China. In the current studies, human milk samples were collected from 30 breastfeeding mothers in Shijiazhuang city (industrialized) and 11 in the Tanshan countryside (agricultural) of Hebei Province in northern China. An additional 20 samples were obtained from mothers in Tokyo, Japan. PCDDs, PCDFs, and dl-PCBs in human milk were analyzed by high-resolution gas chromatography/high-resolution mass spectrometry. Our results show that arithmetic means for body burdens of PCDDs/Fs and dl-PCBs in Hebei were 3.6 and 1.9 pg TEQg(-1) fat, respectively, which were only about one fourth of the levels in Japan. In addition, no difference was found in the chemical levels except dl-PCBs between the urban and rural areas. Based on the results of an in-person interview of the Chinese mothers using a 59-item questionnaire, freshwater fish consumption was found to correlate with the body burden of dioxins. Principal component analysis of dioxin congeners revealed that the patterns of dioxins in the Hebei urban and rural areas are quite similar; however, they are clearly different from those in Japan. Collectively, our results suggest that the lower body burdens of dioxin in Hebei may be due in part to the relatively slow industrialization and a lower consumption of marine foods. Finally, the results indicate that comprehensive monitoring of dioxins and dl-PCBs in humans as well as in the environment and foods is necessary in China.

Effect of dimethyl fumarate on rats with chronic pancreatitis.

OBJECTIVE: To discuss the effect of dimethyl fumarate (DMF) on rats with l-arginine induced chronic pancreatitis (CP). METHODS: Male Wistar rats were given DMF treatment (25 mg/kg) by oral lavage method; then Wistar rats were given the intraperitoneal injection of l-arginine for 5 times (250 mg/100 kg, twice per time, each interval of 1 h) for building of CP model. Rats were divided into control group, CP group, DMF group and CP + DMF group. Rats in CP + DMF group were given the oral intragastric administration of DMF (25 mg/kg), while rats in control group and CP group were given the equal volume of normal saline. The weight of rats was evaluated and the intraperitoneal glucose tolerance test was performed (IPGTT, 2 g/kg). The islet of rats was isolated and then flow cytometry was employed to evaluate the quality and activity of islets. Meanwhile, the histology of non-endocrine tissues and levels of myeloperoxidase (MPO) and malondialdehyde (MDA) were detected. RESULTS: Compared with control group, the weight of rats in CP group was significantly reduced at week 2, 4 and 6; the blood glucose significantly increased, AUC increased, the histopathological scores of pancreatic atrophy, acinar injury, edema and cellular infiltration increased, levels of MDA and MPO increased, the islet equivalent and islet activity decreased at 0, 30, 60, 120 and 180 min. Compared with CP group, the weight of rats in CP + DMF group significantly increased at week 2, 4 and 6; the blood glucose significantly decreased, AUC decreased, the histopathological scores of pancreatic atrophy, acinar injury, edema and cellular infiltration decreased, levels of MDA and MPO decreased, the islet equivalent and islet activity increased at 0, 30, 60, 120 and 180 min. CONCLUSIONS: DMF treatment can improve CP induced by l-arginine and islet function in rats.

Molecular Characterization of Clostridium difficile Isolates from Human Subjects and the Environment.

Clostridium difficile is a spore-forming, gram-positive, anaerobic bacillus that can cause C. difficile infection (CDI). However, only a few studies on the prevalence and antibiotic resistance of C. difficile in healthy individuals in China have been reported. We employed a spore enrichment culture to screen for C. difficile in the stool samples of 3699 healthy Chinese individuals who were divided into 4 groups: infants younger than 2 years of age and living at home with their parents; children aged 1 to 8 years of age and attending three different kindergarten schools; community-dwelling healthy adult aged 23-60 years old; and healthcare workers aged 28-80 years old. The C. difficile isolates were analyzed for the presence of toxin genes and typed by PCR ribotyping and multilocus sequence typing (MLST). The minimum inhibitory concentration of 8 antimicrobial agents was determined for all of the isolates using the agar dilution method. The intestinal carriage rate in the healthy children was 13.6% and ranged from 0% to 21% depending on age. The carriage rates in the 1654 community-dwelling healthy adults and 348 healthcare workers were 5.5% and 6.3%, respectively. Among the isolates, 226 were toxigenic (225 tcdA+/tcdB+ and 1 tcdA+/tcdB+ ctdA+/ctdB+). Twenty-four ribotypes were found, with the dominant type accounting for 29.7% of the isolates. The toxigenic isolates were typed into 27 MLST genotypes. All of the strains were susceptible to vancomycin, metronidazole, fidaxomicin, and rifaximin. High resistance to levofloxacin and ciprofloxacin at rates of 39.8% and 98.3%, respectively, were observed. ST37 isolates were more resistant to levofloxacin than the other STs. The PCR ribotypes and sequence types from the healthy populations were similar to those from the adult patients.

A soy diet accelerates renal damage in autoimmune MRL/Mp-lpr/lpr mice.

Isoflavones, which are phytoestrogens present in large quantities in soy and soy-derived products, have estrogenic activity, inhibit protein tyrosine kinase, and exert other effects in the human body. Thus, the recent spread of soy consumption in Western populations emphasizes the need to more fully understand the potential effects in the body, especially in abnormal immune conditions. In the present study, the influence of a soy diet on lupus disease in MRL/Mp-lpr/lpr (MRL/lpr) mice was investigated. Weanling female MRL/lpr mice (4 weeks) were fed a soy diet (20% soybean protein and 5% soybean oil). The soy diet exacerbated renal damage; findings in this mouse strain included accelerated proteinuria, elevated serum creatinine concentrations, and reduced creatinine clearance. No effects were detected, however, in C3H/HeN mice, which have the same H-2(k) genetic background as MRL/lpr mice do. A tendency toward an increase in thymus weight and proliferation of T cells in spleen and B cells in lymph nodes were found at the age of 16 weeks. These findings indicate that a soy diet, in comparison with a casein diet, significantly exacerbates the clinical course of this autoimmune disease. Further research on the mechanism of this effect of soy-rich diets is needed, and isoflavone supplementation for systemic lupus erythematosus patients should be carefully reevaluated.

[Effect of naloxone on expression of Bcl-2 protein and tumor necrosis factor-alpha in rats with acute myocardial ischemia/reperfusion injury].

OBJECTIVE: To investigate the effect of naloxone on myocardial cell apoptosis and apoptosis-related gene Bcl-2 in rats with acute myocardial ischemia/reperfusion (AMIR) injury, and explore the mechanism of protective effect of naloxone on myocardium. METHODS: Thirty SD rats were randomly divided into three groups (n=10): ischemia/reperfusion group, naloxone preconditioning group (naloxone was injected intraperitoneally 10 minutes before ischemia and 2 hours after reperfusion), and normal control group. The left anterior descending branch (LAD) of rat coronary artery was tied and un-tied in ischemia/reperfusion group and naloxone preconditioning group to establish the AMIR model in rats. The animals were then sacrificed and hearts were harvested. The expression of Bcl-2 protein was observed by immunohistochemical technique. Radioimmunoassay (RIA) was used to determine tumor necrosis factor-alpha (TNF-alpha) in serum. RESULTS: In the normal control group, there was no Bcl-2 expression and TNF-alpha level was (0.39+/-0.06) mug/L. Higher expression of Bcl-2 and increased TNF-alpha levels were found in ischemia/reperfusion group. The expression of Bcl-2 protein increased significantly [(+++) vs. (+)], and TNF-alpha was significantly lower in naloxone preconditioning group than those in the normal control group [(0.55+/-0.12) microg/L vs. (0.86+/-0.11) microg/L, P<0.01]. CONCLUSION: Naloxone can protect myocardium from AMIR injury by inhibiting the apoptosis of cardiomyocytes induced by TNF-alpha and up-regulating protein expression of bcl-2 gene.