Identification of novel variants for complicating cardiac disease in the scrub typhus infection using whole genome sequencing.

BACKGROUND/AIMS: Scrub typhus infection has been known to complicate cardiovascular diseases mainly attributing to high mortality. Genetic susceptibility loci for complicating cardiac diseases such as atrial fibrillation, heart failure, and ischemic heart disease identified by genomic study have been limited in scrub typhus infection. Therefore, we investigated the genetic novel variants predicting complicating cardiac diseases in patients with confirmed scrub typhus infection using whole genome sequencing. METHODS: We performed a prospective study for eight consecutive patients with scrub typhus infection. During follow-up, six cases were clinically diagnosed with complicating cardiac diseases and two controls without complicating cardiac diseases. The whole genomes of the all patients were sequenced, and the individual sequence variants were compared between accordcase and control patients. Variant genotypes were compared and identified as a single nucleotide polymorphism (SNP) of the different genotype distributions between six cases and two controls. RESULTS: The GG genotype in SNP (rs4977397) of solute carrier 24 family member 2 (SLC24A2) gene and non-TT genotype in SNP (rs2676750) of adenosine deaminase, RNA specific, B2 (ADARB2) gene were distinctively found in the case patients with complicated cardiac disease, compared with control patents in the scrub typhus infection. CONCLUSION: We suggest that the SNPs of SLC24A2 and ADARB2 might be genetic surrogate markers for complicating cardiac diseases in the scrub typhus infection. Our study show that early detection based on individual sequence variants might be feasible to predict complicating cardiac diseases in patients with scrub typhus infection, if further studies with more participants confirm these findings.

2018 Korean Society for the Study of Obesity Guideline for the Management of Obesity in Korea.

Obesity increases the risks of diabetes, hypertension, and cardiovascular diseases, ultimately contributing to mortality. Korean Society for the Study of Obesity (KSSO) was established to improve the management of obesity through research and education; to that end, the Committee of Clinical Practice Guidelines of KSSO reviews systemic evidence using expert panels to develop clinical guidelines. The clinical practice guidelines for obesity were revised in 2018 using National Health Insurance Service Health checkup data from 2006 to 2015. Following these guidelines, we added a category, class III obesity, which includes individuals with body mass index (BMI) ≥35 kg/m2. Agreeing with the International Federation for the Surgery of Obesity and Metabolic Disorders, Asian Pacific Chapter consensus, we determined that bariatric surgery is indicated for Korean patients with BMI ≥35 kg/m2 and for Korean patients with BMI ≥30 kg/m2 who have comorbidities. The new guidelines focus on guiding clinicians and patients to manage obesity more effectively. Our recommendations and treatment algorithms can serve as a guide for the evaluation, prevention, and management of overweight and obesity.

Histopathological findings in wild Nutrias (Myocastor coypus) with Capillaria hepatica infection.

Capillaria hepatica is a zoonotic nematode that uses rodents and other mammals as hosts, especially rats and mice, and causes hepatic granuloma and eventually fibrosis/cirrhosis. However, C. hepatica infection in nutria, a large semiaquatic rodent, has rarely been reported, and histopathologic features of the infection have not been described in detail. We conducted necropsy on 36 wild nutrias. Some animals were found to have milky spots, parasitic eggs and worms within hepatic microgranuloma involving central calcification with cell debris, macrophages, eosinophils and multinucleated giant cells (MGCs). Interestingly, the eggs were closely surrounded by MGCs and appeared to be destroyed without inducing further chronic changes. Based on microscopical examination, C. hepatica infection was diagnosed, and we describe its histopathological characteristics in wild nutrias.

Melatonin improves experimental colitis with sleep deprivation.

Sleep deprivation (SD) is an epidemic phenomenon in modern countries, and its harmful effects are well known. SD acts as an aggravating factor in inflammatory bowel disease. Melatonin is a sleep-related neurohormone, also known to have antioxidant and anti-inflammatory effects in the gastrointestinal tract; however, the effects of melatonin on colitis have been poorly characterized. Thus, in this study, we assessed the measurable effects of SD on experimental colitis and the protective effects of melatonin. For this purpose, male imprinting control region (ICR) mice (n = 24) were used; the mice were divided into 4 experimental groups as follows: the control, colitis, colitis with SD and colitis with SD and melatonin groups. Colitis was induced by the administration of 5% dextran sulfate sodium (DSS) in the drinking water for 6 days. The mice were sleep-deprived for 3 days. Changes in body weight, histological analyses of colon tissues and the expression levels of pro-inflammatory cytokines and genes were evaluated. SD aggravated inflammation and these effects were reversed by melatonin in the mice with colitis. In addition, weight loss in the mice with colitis with SD was significantly reduced by the injection of melatonin. Treatment with melatonin led to high survival rates in the mice, in spite of colitis with SD. The levels of pro-inflammatory cytokines, such as interleukin (IL)-1ß, IL-6, IL-17, interferon-γ and tumor necrosis factor-α, in the serum of mice were significantly increased by SD and reduced by melatonin treatment. The melatonin-treated group showed a histological improvement of inflammation. Upon gene analysis, the expression of the inflammatory genes, protein kinase Cζ (PKCζ) and calmodulin 3 (CALM3), was increased by SD, and the levels decreased following treatment with melatonin. The expression levels of the apoptosis-related inducible nitric oxide synthase (iNOS) and wingless-type MMTV integration site family, member 5A (Wnt5a) genes was decreased by SD, but increased following treatment with melatonin. Treatment with melatonin reduced weight loss and prolonged survival in mice with colitis with SD. Melatonin exerted systemic anti-inflammatory effects. Gene analysis revealed a possible mechanism of action of melatonin in inflammation and sleep disturbance. Thus, melatonin may be clinically applicable for patients with inflammatory bowel disease, particularly those suffering from sleep disturbances.

Diastolic Dysfunction Induced by a High-Fat Diet Is Associated with Mitochondrial Abnormality and Adenosine Triphosphate Levels in Rats.

BACKGROUND: Obesity is well-known as a risk factor for heart failure, including diastolic dysfunction. However, this mechanism in high-fat diet (HFD)-induced obese rats remain controversial. The purpose of this study was to investigate whether cardiac dysfunction develops when rats are fed with a HFD for 10 weeks; additionally, we sought to investigate the association between mitochondrial abnormalities, adenosine triphosphate (ATP) levels and cardiac dysfunction. METHODS: We examined myocardia in Wistar rats after 10 weeks of HFD (45 kcal% fat, n=6) or standard diet (SD, n=6). Echocardiography, histomorphologic analysis, and electron microscopy were performed. The expression levels of mitochondrial oxidative phosphorylation (OXPHOS) subunit genes, peroxisome-proliferator-activated receptor γ co-activator-1α (PGC1α) and anti-oxidant enzymes were assessed. Markers of oxidative stress damage, mitochondrial DNA copy number and myocardial ATP level were also examined. RESULTS: After 10 weeks, the body weight of the HFD group (349.6±22.7 g) was significantly higher than that of the SD group (286.8±14.9 g), and the perigonadal and epicardial fat weights of the HFD group were significantly higher than that of the SD group. Histomorphologic and electron microscopic images were similar between the two groups. However, in the myocardium of the HFD group, the expression levels of OXPHOS subunit NDUFB5 in complex I and PGC1α, and the mitochondrial DNA copy number were decreased and the oxidative stress damage marker 8-hydroxydeoxyguanosine was increased, accompanied by reduced ATP levels. CONCLUSION: Diastolic dysfunction was accompanied by the mitochondrial abnormality and reduced ATP levels in the myocardium of 10 weeks-HFD-induced rats.

Novel ERBB receptor feedback inhibitor 1 (ERRFI1) + 808 T/G polymorphism confers protective effect on diabetic nephropathy in a Korean population.

BACKGROUND: The identification and characterization of the gene, ERRFI1, in diabetes has not been reported. In this study, we evaluated the relationship between ERRFI1 polymorphism and characteristics of type 2 diabetes mellitus (T2DM) in Korea. SUBJECTS AND METHODS: We conduct a case-control study involving T2DM patients (n=342) and controls (n=473). RESULTS: A novel single nucleotide ERRFI1 gene polymorphism at +807(T/G) was found. G genotype frequency was 40.1% in the diabetic group and 42.7% in the control group; the difference was not significant (p=0.45). In the diabetic group, the urine albumin to creatinine ratio (ACR) was lower in the G genotype than in the T genotype (P=0.004). In males with T2DM, those with the G genotype displayed lower systolic blood pressure (P=0.01) and higher glomerular filtration rate (P=0.048) compare to those with the T genotype. In females with T2DM, urine ACR was low in those with the G genotype than in those with the T genotype (P=0.02). In the diabetic group, patients who harboring T allele had a 1.81 times higher risk of diabetic nephropathy than the G allele (95% CI 1.11-2.96, P=0.02). In females with T2DM, patients who harboring T allele had a 2.12 times higher risk of diabetic nephropathy (95% CI 1.07-4.1, P=0.03). CONCLUSIONS: We identify new loci associated with glycemic traits in diabetes and this finding indicates the potential of ERRFI1 as a novel therapeutic target of diabetic nephropathy.

Exendin-4 increases bone mineral density in type 2 diabetic OLETF rats potentially through the down-regulation of SOST/sclerostin in osteocytes.

AIM: Glucagon-like peptide-1 (GLP-1) receptor participates in the control of bone resorption in GLP-1 knockout mice. Also, GLP-1 induces an insulin- and parathyroid hormone-independent osteogenic action through osteoclasts and osteoblasts in insulin-resistant and type 2 diabetic rats. Osteocytes are now considered central to bone homeostasis. A secreted product of osteocytes, sclerostin, inhibits bone formation. However, the effect of GLP-1 on osteocytes remains unclear. Therefore, we investigated the effect of GLP-1 on bone mineral density (BMD), and the cellular and molecular mechanisms associated with osteocytes. MAIN METHODS: We investigated the presence of GLP-1 receptors in osteocyte-like MLO-Y4 cells and osteocytes of rat femurs through RT-PCR, Western blot and confocal microscopy, and investigated the effect of exendin-4 on the expression of mRNA (by quantitative real-time RT-PCR) and protein (by Western blot) of SOST/sclerostin in osteocyte-like MLO-Y4 cells during culture under normal or high-glucose (30 mM) conditions, and measured circulating levels of sclerostin, osteocalcin, and tartrate-resistant alkaline phosphatase (TRAP) 5b and femoral BMD in type 2 diabetic OLETF rats treated with exendin-4. KEY FINDINGS: GLP-1 receptor was present on MLO-Y4 cells and osteocytes of rat femurs. Exendin-4 reduced the mRNA expression and protein production of SOST/sclerostin under normal or high-glucose conditions in MLO-Y4 cells. Exendin-4 reduced serum levels of sclerostin, increased serum levels of osteocalcin, and increased femoral BMD in type 2 diabetic OLETF rats. SIGNIFICANCE: These findings suggest that exendin-4 might increase BMD by decreasing the expression of SOST/sclerostin in osteocytes in type 2 diabetes.

17ß-estradiol induces an interaction between adenosine monophosphate-activated protein kinase and the insulin signaling pathway in 3T3-L1 adipocytes.

Estrogen (17ß-estradiol) has been implicated in maintaining insulin sensitivity. It is thought to act predominantly through genomic pathways and regulate the expression of various genes via binding to estrogen receptors (ERs)-α and -ß. 17ß-estradiol has been reported to simultaneously stimulate protein kinase B (Akt) and adenosine monophosphate-activated protein kinase (AMPK) in ex vivo skeletal muscle. Since data regarding the interaction between AMPK and the insulin receptor substrate-1 (IRS-1)/Akt pathway are controversial, the correlation between AMPK activation and insulin signaling remains unclear. In this study, we examined whether 17ß-estradiol simultaneously stimulates the activation of AMPK and IRS-1/Akt in 3T3-L1 adipocytes as well as the 17ß-estradiol-ER-induced interaction between the AMPK and IRS-1/Akt pathway in 3T3-L1 adipocytes not exposed to insulin. 17ß-estradiol (10⁻7 M) rapidly activated AMPK and IRS-1/Akt in 3T3-L1 adipocytes, while the ER-α/ß non-specific antagonist, ICI 182.780 (10 µM), and the AMPK antagonist compound C (20 µM) reversed the estrogen-induced activation of AMPK and tyrosine (Tyr)-IRS-1/Akt in these cells. Moreover, 17ß-estradiol increased the expression of the peroxisome proliferator-activated receptor-γ coactivator-1α (PGC1α), adiponectin, uncoupling protein 2 (UCP2) and glucose transporter 4 (GLUT4) genes 24 h after treatment, whereas the ER-α/ß non-specific antagonist, ICI 182.780 (10 µM), and the AMPK antagonist compound C (20 µM) reversed the estrogen-induced increase in the expression of these genes. These results indicate that 17ß-estradiol activates AMPK through an ER and activates Akt through AMPK activation in 3T3-L1 adipocytes, despite the absence of insulin. Furthermore, 17ß-estradiol regulates the expression of genes related to glucose metabolism through ER-AMPK activation in these cells.

A novel mutation of exon 7 in growth hormone receptor mRNA in a patient with growth hormone insensitivity syndrome and neurofibromatosis type I.

Growth hormone insensitivity syndrome (GHIS), a genetic disease characterized by growth retardation combined with high serum concentration of growth hormone (GH) and low insulin-like growth factor 1 (IGF-1) levels, can be caused by mutations in the GH receptor (GHR) gene. We investigated the molecular defects in the GHR gene in a patient with neurofibromatosis type 1 (NF-1). The patient, a 2-year-old boy with NF-1, was assessed on his short stature by auxological, biochemical and molecular studies. Height of the patient and his family members were measured and compared to normal control. Serum concentrations of GH, IGF-1 and IGF-binding protein 3 (IGFBP3) in the patient were measured during a GH stimulation test. We examined the GHR gene in the patient and his parents. Genomic DNA and mRNA of the GHR gene were extracted from peripheral lymphocytes. All the exons and the flanking regions of the GHR gene were amplified by PCR, and directly sequenced. The patient's height was 75 cm (-2.89 SDS) with gradually reducing growth velocity, while the heights of the other family members were within the normal range. The GH stimulation test revealed that serum GH concentrations in the patient were much higher than those in the control group, and serum IGF-1 and IGFBP3 levels were extremely low. There was no germline mutation in the exons or the flanking regions of the patient's GHR gene. Interestingly, a deletion of 166 bases of exon 7 in the GHR mRNA was found, and it was suggested that the novel mutation resulted in premature termination (M207 fs. X8). This mutation decreases GH binding affinity to the GHR, and, thus, would be responsible for growth retardation.

Melatonin improves inflammatory cytokine profiles in lung inflammation associated with sleep deprivation.

Sleep disturbance has become an endemic behavior in modern countries, and its prevalence has also increased. Even a subtle sleep deficiency is related to health problems. Particularly, patients with pulmonary disease often complain of insomnia. We recently showed that sleep deprivation (SD) exacerbates existing acute lung inflammation, and that melatonin treatment attenuates it via anti-apoptotic and anti-oxidant action. In order to reinforce our previous report, the present study was designed to evaluate pro-inflammatory mediators in acute lung inflammation in SD mice. In addition, we investigated the infiltration of inflammatory cells into the lungs. Twenty-five ICR mice were divided into 5 groups (n=5/group): control, SD, lipopolysaccharide (LPS), LPS + SD and LPS + SD + melatonin. The SD mice were deprived of sleep for 96 h in a multiplatform water bath. LPS (5 mg/kg) and melatonin (5 mg/kg) were administered on day 2. The mice were sacrificed on day 3, and serum and bronchoalveolar lavage (BAL) fluid were collected. The serum levels of inflammatory cytokines were increased in the LPS + SD group. Interleukin-6, tumor necrosis factor-α and interferon-γ levels were also increased in BAL fluid in the LPS + SD group. Melatonin reduced inflammatory mediators in the serum and BAL fluid. The accumulation of leukocytes in the LPS and LPS + SD mice was elevated, however, melatonin inhibited the recruitment of inflammatory cells (p<0.05). Lymphocytes in the BAL fluid of the LPS + SD group were increased, and macrophage levels were decreased; however, the increment was attenuated by melatonin administration (p<0.05). In conclusion, this study indicates that melatonin has a protective effect against lung inflammation associated with SD.

Exendin-4 protects against sulfonylurea-induced ß-cell apoptosis.

Sulfonylurea is one of the commonly used anti-diabetic drugs that stimulate insulin secretion from ß-cells. Despite their glucose lowering effects in type 2 diabetes mellitus, long-term treatment brought on secondary failure characterized by ß-cell exhaustion and apoptosis. ER stress induced by Ca(2+) depletion in endoplasmic reticulum (ER) is speculated be one of the causes of secondary failure, but it remains unclear. Glucagon like peptide-1 (GLP-1) has anti-apoptotic effects in ß-cells after the induction of oxidative and ER stress. In this study, we examined the anti-apoptotic action of a GLP-1 analogue in ß-cell lines and islets against ER stress induced by chronic treatment of sulfonylurea. HIT-T15 and dispersed islet cells were exposed to glibenclamide for 48 h, and apoptosis was evaluated using Annexin/PI flow cytometry. Expression of the ER stress-related molecules and sarco/endoplasmic reticulum Ca(2+)-ATPase (SERCA) 2/3 was determined by real-time PCR and western blot analysis. Chronic exposure to glibenclamide increased apoptosis by depletion of ER Ca(2+) concentration through reduced expression of SERCA 2/3. Pretreatment with Exendin-4 had an anti-apoptotic role through ER stress modulation and ER Ca(2+) replenishing by SERCA restoration. These findings will further the understanding of one cause of glibenclamide-induced ß-cell loss and therapeutic availability of GLP-1-based drugs in secondary failure by sulfonylurea during treatment of diabetes.

Exendin-4 protects oxidative stress-induced ß-cell apoptosis through reduced JNK and GSK3ß activity.

Oxidative stress induced by chronic hyperglycemia in type 2 diabetes plays a crucial role in progressive loss of ß-cell mass through ß-cell apoptosis. Glucagon like peptide-1 (GLP-1) has effects on preservation of ß-cell mass and its insulin secretory function. GLP-1 possibly increases islet cell mass through stimulated proliferation from ß-cell and differentiation to ß-cell from progenitor cells. Also, it probably has an antiapoptotic effect on ß-cell, but detailed mechanisms are not proven. Therefore, we examined the protective mechanism of GLP-1 in ß-cell after induction of oxidative stress. The cell apoptosis decreased to ~50% when cells were treated with 100 µM H(2)O(2) for up to 2 hr. After pretreatment of Ex-4, GLP-1 receptor agonist, flow cytometric analysis shows 41.7% reduction of ß-cell apoptosis. This data suggested that pretreatment of Ex-4 protect from oxidative stress-induced apoptosis. Also, Ex-4 treatment decreased GSK3ß activation, JNK phosphorylation and caspase-9, -3 activation and recovered the expression of insulin2 mRNA in ß-cell lines and secretion of insulin in human islet. These results suggest that Ex-4 may protect ß-cell apoptosis by blocking the JNK and GSK3ß mediated apoptotic pathway.

Vascular endothelial growth factor, fms-like tyrosine kinase-1 (Flt-1) and soluble Flt-1 gene expressions in Korean pre-eclamptic placentas.

AIM: To assess the expressions of vascular endothelial growth factor (VEGF), fms-like tyrosine kinase-1 (Flt-1), and soluble Flt-1 (sFlt-1) genes in healthy normotensive and pre-eclamptic placentas of Korean women. METHODS: We investigated 12 healthy normotensive pregnant women and 10 pre-eclamptic pregnant women at Eulji University Hospital. The obtained placental tissues were analyzed using reverse transcription polymerase chain reaction and real-time quantitative polymerase chain reaction. RESULTS: The sFlt-1 messenger ribonucleic acid (mRNA) level was elevated 2.6 times more in pre-eclamptic placentas than in normal control placentas. However, the VEGF mRNA level of pre-eclamptic placentas was decreased. There was no difference in the Flt-1 mRNA level between control and pre-eclamptic placentas. CONCLUSIONS: Our study showed that expressions of genes relating to angiogenesis were altered in Korean pre-eclamptic placentas. These results suggest that the alteration in expressions of sFlt-1 and VEGF genes might be associated with the pathogenesis of pre-eclampsia.

Parenteral 17beta-estradiol decreases fasting blood glucose levels in non-obese mice with short-term ovariectomy.

AIMS: long-term ovariectomy-induced metabolic changes such as insulin resistance and glucose intolerance might be caused directly by estrogen deficiency and may occur partly as secondary effects of obesity arising due to the orexigenic effects of estrogen deficiency. Long-term estrogen treatment prevented those by exerting anorexigenic and metabolic actions in ovariectomized mice. However, the effect of short-term estrogen treatment on glucose metabolism in mice with short-term ovariectomy, during which ovariectomy-induced obesity does not develop, is not yet clear. The aim of this study was to evaluate the effect of short-term parenteral 17beta-estradiol treatment on glucose metabolism and blood glucose levels in mice at 2 weeks after ovariectomy, a time period during which ovariectomy-induced obesity does not develop. MAIN METHODS: we examined the effect of three 17beta-estradiol injections on fasting blood glucose levels, insulin resistance, components of the insulin signaling pathway, AMPK activation, and the expression of genes related to glucose metabolism in liver, skeletal muscle, and white adipose tissues of non-obese C57BL/6N mice with short-term ovariectomy. KEY FINDINGS: three 17beta-estradiol injections decreased the fasting blood glucose levels, activated AMPK, and decreased the expression of gluconeogenic genes, phosphoenolpyruvate carboxykinase, glucose-6-phosphatase and peroxisome proliferator-activated receptor-γ coactivator-1α in the liver. But three 17beta-estradiol injections did not affect insulin sensitivity and the components of the insulin signaling pathway in the liver and skeletal muscle. SIGNIFICANCE: short-term parenteral 17beta-estradiol treatment decreases the fasting blood glucose levels not via insulin sensitivity of the skeletal muscle in non-obese mice with short-term ovariectomy.

Apoptotic effect of EGCG in HT-29 colon cancer cells via AMPK signal pathway.

EGCG [(-)epigallocatechin-3-gallate], a green tea-derived polyphenol, has been shown to suppress cancer cell proliferation, and interfere with the several signaling pathways and induce apoptosis. Practically, there is emerging evidence that EGCG has a potential to increase the efficacy of chemotherapy in patients. We hypothesized that EGCG may exert cell cytotoxicity through modulating AMPK (AMP-activated protein kinase) followed by the decrease in COX-2 expression. EGCG treatment to colon cancer cells resulted in a strong activation of AMPK and an inhibition of COX-2 expression. The decreased COX-2 expression as well as prostaglandin E(2) secretion by EGCG was completely abolished by inhibiting AMPK by an AMPK inhibitor, Compound C. Also, the activation of AMPK was accompanied with the reduction of VEGF (vascular endothelial growth factor) and glucose transporter, Glut-1 in EGCG-treated cancer cells. These findings support the regulatory role of AMPK in COX-2 expression in EGCG-treated cancer cells. Furthermore, we have found that reactive oxygen species (ROS) is an upstream signal of AMPK, and the combined treatment of EGCG and chemotherapeutic agents, 5-FU or Etoposide, exert a novel therapeutic effect on chemo-resistant colon cancer cells. AMPK, a molecule of newly defined cancer target, was shown to control COX-2 in EGCG-treated colon cancer cells.

Selenium regulates cyclooxygenase-2 and extracellular signal-regulated kinase signaling pathways by activating AMP-activated protein kinase in colon cancer cells.

Epidemiologic and experimental evidences indicate that selenium, an essential trace element, can reduce the risk of a variety of cancers. Protection against certain types of cancers, particularly colorectal cancers, is closely associated with pathways involving cyclooxygenase-2 (COX-2). We found that AMP-activated protein kinase (AMPK), which functions as a cellular energy sensor, mediates critical anticancer effects of selenium via a COX-2/prostaglandin E(2) signaling pathway. Selenium activated AMPK in tumor xenografts as well as in colon cancer cell lines, and this activation seemed to be essential to the decrease in COX-2 expressions. Transduction with dominant-negative AMPK into colon cancer cells or application of cox-2(-/-)-negative cells supported the evidence that AMPK is an upstream signal of COX-2 and inhibits cell proliferation. In HT-29 colon cancer cells, carcinogenic agent 12-O-tetradecanoylphorbol-13-acetate (TPA) activated extracellular signal-regulated kinase (ERK) that led to COX-2 expression and selenium blocked the TPA-induced ERK and COX-2 activation via AMPK. We also showed the role of a reactive oxygen species as an AMPK activation signal in selenium-treated cells. We propose that AMPK is a novel and critical regulatory component in selenium-induced cancer cell death, further implying AMPK as a prime target of tumorigenesis.

Outer membrane protein 38 of Acinetobacter baumannii localizes to the mitochondria and induces apoptosis of epithelial cells.

Acinetobacter baumannii is an important opportunistic pathogen responsible for nosocomial infection. Despite considerable clinical and epidemiological data regarding the role of A. baumannii in nosocomial infection, the specific virulence factor or pathogenic mechanism of this organism has yet to be elucidated. This study investigated the molecular mechanism of apoptosis on the infection of human laryngeal epithelial HEp-2 cells with A. baumannii and examined the contribution of outer membrane protein 38 (Omp38) on the ability of A. baumannii to induce apoptosis of epithelial cells. A. baumannii induced apoptosis of HEp-2 cells through cell surface death receptors and mitochondrial disintegration. The Omp38-deficient mutant was not as able to induce apoptosis as the wild-type A. baumannii strain. Purified Omp38 entered the cells and was localized to the mitochondria, which led to a release of proapoptotic molecules such as cytochrome c and apoptosis-inducing factor (AIF). The activation of caspase-3, which is activated by caspase-9, degraded DNA approximately 180 bp in size, which resulted in the appearance of a characteristic DNA ladder. AIF degraded chromosomal DNA approximately 50 kb in size, which resulted in large-scale DNA fragmentation. These results demonstrate that Omp38 may act as a potential virulence factor to induce apoptosis of epithelial cells in the early stage of A. baumannii infection.