Ribosomal protein S3 associates with the TFIIH complex and positively regulates nucleotide excision repair.

In mammalian cells, the bulky DNA adducts caused by ultraviolet radiation are mainly repaired via the nucleotide excision repair (NER) pathway; some defects in this pathway lead to a genetic disorder known as xeroderma pigmentosum (XP). Ribosomal protein S3 (rpS3), a constituent of the 40S ribosomal subunit, is a multi-functional protein with various extra-ribosomal functions, including a role in the cellular stress response and DNA repair-related activities. We report that rpS3 associates with transcription factor IIH (TFIIH) via an interaction with the xeroderma pigmentosum complementation group D (XPD) protein and complements its function in the NER pathway. For optimal repair of UV-induced duplex DNA lesions, the strong helicase activity of the TFIIH complex is required for unwinding damaged DNA around the lesion. Here, we show that XP-D cells overexpressing rpS3 showed markedly increased resistance to UV radiation through XPD and rpS3 interaction. Additionally, the knockdown of rpS3 caused reduced NER efficiency in HeLa cells and the overexpression of rpS3 partially restored helicase activity of the TFIIH complex of XP-D cells in vitro. We also present data suggesting that rpS3 is involved in post-excision processing in NER, assisting TFIIH in expediting the repair process by increasing its turnover rate when DNA is damaged. We propose that rpS3 is an accessory protein of the NER pathway and its recruitment to the repair machinery augments repair efficiency upon UV damage by enhancing XPD helicase function and increasing its turnover rate.

Relationships between subjective taste sensations and electrogustometry findings in patients with taste disorders.

This study aimed to examine the relationships between subjective taste sensations and electrogustometry (EGM) findings in patients with taste disturbances according to the presence of burning mouth (BM) symptoms. Forty-six patients were included and asked to complete a questionnaire that contained questions on subjective taste sensations for the four basic taste qualities and the pattern of taste disorders such as ageusia, hypogeusia and dysgeusia. EGM was performed to measure detection thresholds. To examine the influence of BM symptoms, patients were divided into two groups: patients with and without BM symptoms. The patients consisted of 11 men and 35 women. The group without BM symptoms (n=26) had significantly lower degrees of subjective taste sensations for all taste qualities and higher correlation levels between subjective taste sensations and EGM thresholds than the group with BM symptoms (n=20). The patterns of taste disorders also showed more significant associations with the levels of subjective taste sensations in the patients without BM symptoms compared with those with BM symptoms. In conclusion, patients with taste disorders without BM symptoms had more severe taste disturbances than those with BM symptoms. The pathophysiology of taste disturbances differs according to the presence or absence of BM symptoms.

Annual prevalence and economic burden of genital warts in Korea: Health Insurance Review and Assessment (HIRA) service data from 2007 to 2015.

This study evaluated the annual prevalence of anogenital warts (AGW) caused by human papillomavirus (HPV) and analysed the trend in annual per cent changes (APC) by using national claims data from the Health Insurance Review and Assessment of Korea, 2007-2015. We also estimated the socio-economic burden and co-morbidities of AGW. All analyses were performed based on data for primary A63.0, the specific diagnosis code for AGW. The socio-economic cost of AGW was calculated based on the direct medical cost, direct non-medical cost and indirect cost. The overall AGW prevalence and socio-economic burden has increased during the last 9 years. However, the prevalence of AGW differed significantly by sex. The female prevalence increased until 2012, and decreased thereafter (APC + 3·6%). It would fall after the introduction of routine HPV vaccination, principally for females, in Korea. The male prevalence increased continuously over time (APC + 11·6%), especially in those aged 20-49 years. Referring to the increasing AGW prevalence and its disease burden, active HPV infection control surveillance and prevention in males are worth consideration.

The utility of intra-operative frozen section for the evaluation of microscopic extrathyroidal extension in papillary thyroid carcinoma.

OBJECTIVES: This study was designed to evaluate the usefulness of intra-operative frozen section for the evaluation of microscopic extrathyroidal extension (ETE) in papillary thyroid carcinoma (PTC). DESIGN: Retrospective cohort study. SETTING: Dong-A University Medical Center, Busan, Korea. PARTICIPANTS: Three hundred and sixty-four patients who underwent thyroid surgery from January 2000 to December 2010 with PTC confined to one unilateral lobe as diagnosed using preoperative ultrasonography were enrolled. MAIN OUTCOME MEASURES: The patients who had microscopic ETE on frozen section were classified into "group A," and those who did not have microscopic ETE on frozen section were classified into "group B." Clinicopathologic factors including age, gender, size of the tumour, extent of operation, ETE, multifocality, bilaterality, lymph node metastasis and recurrence were compared between the two groups. RESULTS: Of the 364 patients enrolled, ETE was confirmed in 100 patients (group A, 27.5%) on frozen biopsy. The nodule size in group A (0.94±0.87 cm) was larger than that in group B (0.86±0.79 cm) (P=.042). In group A, 15 patients (15%) showed multifocality and 11 patients (14.47%) showed bilaterality. In group B, 37 patients (14.02%) showed multifocality and seven patients (43.35%) showed bilaterality. They did not differ significantly between the two groups (P=.811, P=.182). There was a higher frequency of lymph node metastases in group A (52/86, 60.47%) than in group B (7/16, 43.75%, P=.214). Recurrence was observed in only two patients who had received thyroid lobectomy as the initial surgery in group A. CONCLUSIONS: Intra-operative frozen biopsy can be a useful method for identifying the microscopic ETE. During the surgery, it can also help the surgeon to decide the optimal extent of surgery and the need for central compartment neck dissection in PTC patients.

TET-mediated hydroxymethylcytosine at the Pparγ locus is required for initiation of adipogenic differentiation.

BACKGROUND/OBJECTIVES: Adipose tissue is one of the main organs regulating energy homeostasis via energy storage as well as endocrine function. The adipocyte cell number is largely determined by adipogenesis. While the molecular mechanism of adipogenesis has been extensively studied, its role in dynamic DNA methylation plasticity remains unclear. Recently, it has been shown that Tet methylcytosine dioxygenase (TET) is catalytically capable of oxidizing DNA 5-methylcytosine (5-mC) to 5-hydroxymethylcytosine (5-hmC) toward a complete removal of the methylated cytosine. We investigate whether expression of the Tet genes and production of hydroxymethylcytosine are required for preadipocyte differentiation. SUBJECTS/METHODS: Murine 3T3-L1 preadipocytes were used to evaluate the role of Tet1 and Tet2 genes during adipogenesis. Changes in adipogenic ability and in epigenetic status were analyzed, with and without interfering Tet1 and Tet2 expression using small interfering RNA (siRNA). The adipogenesis was evaluated by Oil-Red-O staining and induced expression of adipogenic genes using quantitative polymerase chain reaction (qPCR). Levels of 5-hmC and 5-mC were measured by MassARRAY, immunoprecipitation and GC mass spectrometry at specific loci as well as globally. RESULTS: Both Tet1 and Tet2 genes were upregulated in a time-dependent manner, accompanied by increased expression of hallmark adipogenic genes such as Pparγ and Fabp4 (P<0.05). The TET upregulation led to reduced DNA methylation and elevated hydroxymethylcytosine, both globally and specifically at the Pparγ locus (P<0.05 and P<0.01, respectively). Knockdown of Tet1 and Tet2 blocked adipogenesis (P<0.01) by repression of Pparγ expression (P<0.05). In particular, Tet2 knockdown repressed conversion of 5-mC to 5-hmC at the Pparγ locus (P<0.01). Moreover, vitamin C treatment enhanced adipogenesis (P<0.05), while fumarate treatment inhibited it (P<0.01) by modulating TET activities. CONCLUSIONS: TET proteins, particularly TET2, were required for adipogenesis by modulating DNA methylation at the Pparγ locus, subsequently by inducing Pparγ gene expression.

Recent Results of In Situ Abdominal Aortic Reconstruction with Cryopreserved Arterial Allograft.

OBJECTIVE: To evaluate treatment outcomes of in situ abdominal aortic reconstruction with cryopreserved arterial allograft (CAA) for patients with abdominal aortic infection. MATERIALS AND METHODS: A retrospective review of prospectively collected data was conducted of patients who underwent in situ aortic reconstruction using CAA for primary, secondary, or prosthetic infection of the abdominal aorta between May 2006 and July 2015, at a single institution. Clinical presentation, indications for treatment, procedural details, early post-operative mortality and morbidity, late death, and graft related complications during the follow up period were investigated. Patient survival and event free survival (any death or re-operation) were calculated using the Kaplan-Meier method. RESULTS: Twenty-five patients (male, n = 20, 80%; mean age, 70.2 ± 8.7 years) underwent in situ abdominal aortic reconstruction (48% aortic, 52% aorto-bi-iliac) with vessel size and ABO matched CAA for treatment of abdominal aortic infection caused by infected abdominal aortic aneurysm (n = 15), aortic prosthesis infection (n = 7), aortic reconstruction with concomitant colon resection (n = 2), and primary suppurative aortitis (n = 1). The median follow up was 19.1 months (range 1-73 months). There were seven post-operative deaths including two (8%) early (<30 days) and five (20%) late deaths There were three (12%) graft related complications including thrombotic occlusion of the CAA, aneurysmal dilatation, and aorto-enteric fistula. Three years after CAA implantation, patient survival was 74% and the event free survival was 58%. CONCLUSIONS: It is believed that in situ abdominal aortic reconstruction with CAA is a useful option for treating primary, secondary, or prosthetic infection of the abdominal aorta.

Whole-breast US following mammography and breast MRI in newly diagnosed breast cancer patients: can it be more than just a guidance tool for biopsy?

AIM: To evaluate the role of ultrasound (US) following magnetic resonance imaging (MRI) and mammography in patients with newly diagnosed breast cancers by assessing the additional cancer detection rate of US. MATERIAL AND METHODS: Two hundred and twenty-five women who had undergone 225 MRI examinations followed by US were included. An US-detected additional cancer was defined as a lesion detected using breast US that had not been detected by MRI, and which was shown to be malignant at histopathology. The rate of additional cancer detection, incidence of additional malignancies, positive predictive value (PPV), and false-positive (FP) rate were analysed. Factors associated with an increase in the additional cancer detection rate were analysed. RESULTS: The additional cancer detection rate was 0% (0/225) for the ipsilateral breast and 0.9% (2/225) for the contralateral breast, and the PPVs were 0% (0/5) and 100% (2/2), respectively. The overall TP:FP ratio was 0.4 (2:5). The additional cancer detection rate was higher for cases with moderate and severe background parenchymal enhancement than cases with minimal and mild background parenchymal enhancement (p=0.003). The additional cancer detection rate for cases with moderate and severe background parenchymal enhancement was 5.7% (2/35) for the contralateral breast (p=0.003). CONCLUSION: Preoperative breast US following MRI and mammography can help clinicians screen for contralateral cancers with an additional detection rate of 0.9%. Moreover, whole-breast US might be a useful contralateral screening modality in cases with moderate or marked parenchymal enhancement on breast MRI.

Sodium nitroprusside suppresses male fertility in vitro.

Sodium nitroprusside is a nitric oxide donor involved in the regulation of the motility, hyperactivation, capacitation, and acrosome reaction (AR) of spermatozoa. However, the molecular mechanism underlying this regulation has not yet been elucidated. Therefore, this study was designed to evaluate the molecular basis for the effects of sodium nitroprusside on different processes in spermatozoa and its consequences on subsequent oocyte fertilization and embryo development. In this in vitro study, mouse spermatozoa were incubated with various concentrations of sodium nitroprusside (1, 10, and 100 µM) for 90 min. Our results showed that sodium nitroprusside inhibited sperm motility and motion kinematics in a dose-dependent manner by significantly enhancing intracellular iron and reactive oxygen species (ROS), and decreasing Ca(2+), and adenosine triphosphate levels in spermatozoa. Moreover, short-term exposure of spermatozoa to sodium nitroprusside increased the tyrosine phosphorylation of sperm proteins involved in PKA-dependent regulation of intracellular calcium levels, which induced a robust AR. Finally, sodium nitroprusside significantly decreased the rates of fertilization and blastocyst formation during embryo development. Based on these results, we propose that sodium nitroprusside increases ROS production and precocious AR may alter overall sperm physiology, leading to poor fertilization and compromised embryonic development.

Prediction of subclinical atherosclerosis by serum osteoprotegerin in premenopausal women with systemic lupus erythematous: correlation of osteoprotegerin with monocyte chemotactic protein-1.

OBJECTIVE: Patients with systemic lupus erythematosus (SLE) have increased risk for cardiovascular disease. Previous studies disclosed the association of serum osteoprotegerin (OPG) with the presence of symptomatic atherosclerosis in the general population and several disease conditions. We thus investigated the association between serum OPG levels and subclinical atherosclerosis in premenopausal SLE patients. METHODS: Serum OPG levels and carotid artery intima-media thickness (IMT) were measured in 181 premenopausal SLE patients and age-matched 85 control subjects. Traditional cardiovascular risk factors and SLE-related factors were analyzed. RESULTS: Patients with SLE had significantly increased serum OPG levels (1086 versus 517 pg/ml, p < 0.001) and carotid IMT (0.63 versus 0.45 mm, p < 0.001) compared with control subjects. Carotid IMT significantly increased across the quartiles of OPG. Logistic regression analysis revealed that compared to the lowest OPG quartile, the odds ratio (OR, 95% confidence interval) for increased carotid IMT in quartile 2, 3, and 4 was 1.126 (1.013-1.801), 1.562 (1.268-2.799), and 4.460 (1.126-7.128), respectively, after multiple adjustments (p for trend across quartiles < 0.001). These associations remained significant after further adjustment for inflammatory parameters. Interestingly, serum monocyte chemotactic protein-1 (MCP-1) levels were positively correlated with serum OPG levels (γ = 0.332, p < 0.001). Parallel analysis showed that serum MCP-1 was also an independent predictor of carotid IMT incrassation, but this association was lost when serum OPG was included in the model. CONCLUSION: Serum OPG levels were increased and correlated with serum MCP-1 levels in premenopausal SLE patients. Increased serum OPG was independently associated with subclinical atherosclerosis in these patients.

Monitoring differentiated thyroid cancer patients with negative serum thyroglobulin. Diagnostic implication of TSH-stimulated antithyroglobulin antibody.

AIM: Serum antithyroglobulin antibody (TgAb) has been reported as a surrogate marker for differentiated thyroid cancer (DTC) in some conditions. We investigated changes in serum TgAb levels after stimulation with thyroid-stimulating hormone (TSH) and the clinical implications for monitoring DTC. PATIENTS, METHODS: We retrospectively enrolled 53 DTC patients who had undergone total thyroidectomy and were negative for serum Tg and positive for TgAb. Patients underwent high-dose radioactive iodine treatment, and serum TgAb was measured before (TgAbBAS) and after TSH stimulation (TgAbSTIM). TgAb was followed up 6 to 12 months later (TgAbF/U). The change in TgAb after TSH stimulation (∆TgAbSTIM) was calculated as a percentage of the baseline level. Patient disease status was classified into no residual disease (ND) and residual or recurred disease (RD) by follow-up imaging studies and pathologic data. The characteristics and diagnostic value of serum TgAb levels and ∆ TgAbSTIM were investigated with respect to disease status. RESULTS: 38 patients were in the ND group and 15 were in the RD group. TgAbBAS, TgAbSTIM and TgAbF/U were significantly higher in the RD compared to the ND group (p = 0.0008, 0.0002, and < 0.0001, respectively). ∆TgAbSTIM was also significantly higher in the RD group (p = 0.0009). In the patients who presented with obviously high (≥ 50%) or low (< -50%) ∆ TgAbSTIM, the proportions in the RD group were markedly different at 100% and 7%, respectively. ∆ TgAbSTIM had significant diagnostic value for RD (p < 0.001). CONCLUSION: The change in serum TgAb level after TSH stimulation is different between the RD and ND groups, and thus, it may be used as a surrogate diagnostic marker for DTC when the serum Tg is negative and TgAb is positive.

Interfractional variability in intensity-modulated radiotherapy of prostate cancer with or without thermoplastic pelvic immobilization.

PURPOSE: To determine the variability of patient positioning errors associated with intensity-modulated radiotherapy (IMRT) for prostate cancer and to assess the impact of thermoplastic pelvic immobilization on these errors using kilovoltage (kV) cone-beam computed tomography (CBCT). MATERIALS AND METHODS: From February 2012 to June 2012, the records of 314 IMRT sessions in 19 patients with prostate cancer, performed with or without immobilization at two different facilities in the Korea University Hospital were analyzed. The kV CBCT images were matched to simulation computed tomography (CT) images to determine the simulation-to-treatment variability. The shifts along the x (lateral)-, y (longitudinal)- and z (vertical)-axes were measured, as was the shift in the three dimensional (3D) vector. RESULTS: The measured systematic errors in the immobilized group during treatment were 0.46 ± 1.75 mm along the x-axis, - 0.35 ± 3.83 mm along the y-axis, 0.20 ± 2.75 mm along the z-axis and 4.05 ± 3.02 mm in the 3D vector. Those of nonimmobilized group were - 1.45 ± 7.50 mm along the x-axis, 1.89 ± 5.07 mm along the y-axis, 0.28 ± 3.81 mm along the z-axis and 8.90 ± 4.79 mm in the 3D vector. The group immobilized with pelvic thermoplastics showed reduced interfractional variability along the x- and y-axes and in the 3D vector compared to the nonimmobilized group (p < 0.05). CONCLUSION: IMRT with thermoplastic pelvic immobilization in patients with prostate cancer appears to be useful in stabilizing interfractional variability during the planned treatment course.

Enhanced antitumor immunotherapeutic effect of B-cell-based vaccine transduced with modified adenoviral vector containing type 35 fiber structures.

For successful clinical tumor immunotherapy outcomes, strong immune responses against tumor antigens must be generated. Cell-based vaccines compromise one strategy with which to induce appropriate strong immune responses. Previously, we established a natural killer T-cell (NKT) ligand-loaded, adenoviral vector-transduced B-cell-based anticancer cellular vaccine. To enhance tumor antigen delivery to B cells, we established a modified adenoviral vector (Ad-k35) that encoded a truncated form of the breast cancer antigen Her2/neu (Ad-k35HM) in which fiber structure was substituted with adenovirus serotype 35. We observed increased tumor antigen expression with Ad-k35HM in both human and murine B cells. In addition, an Ad-k35HM-transduced B-cell vaccine elicited strong antigen-specific cellular and humoral immune responses that were further enhanced with the additional loading of soluble NKT ligand KBC009. An Ad-k35HM-transduced, KBC009-loaded B-cell vaccine efficiently suppressed the in vivo growth of established tumors in a mouse model. Moreover, the vaccine elicited human leukocyte antigen (HLA)-A2 epitope-specific cytotoxic T-cell responses in B6.Cg (CB)-Tg (HLA-A/H2-D) 2Enge/Jat mice. These findings indicated that the Ad-k35 could be appropriate for the preclinical and clinical development of B-cell-based anticancer immunotherapies.

Automated screening for tuberculosis by multiparametric analysis of data obtained during routine complete blood count.

INTRODUCTION: The main goal of this study was to develop a multiparametric cell population data (CPD) model that combines information from several morphologic parameters generated by DxH800, in addition to the traditional parameters regularly reported in the CBC-diff, and to test the performance of this model in screening the general population for primary tuberculosis (TB). METHODS: A total of 3741 study cases were divided into two groups, test and validation set at cut-off value of 6000 WBCs/µL. We developed multiparametric model for primary TB screening (TB hemeprint), selected CPD, and calculated parameters which could discriminate primary TB from other non-TB diseases and normal control in test set. We applied it to the validation set, which was a set of completely different samples, to test its reproducibility if applied to a routine laboratory test. RESULTS: After screening primary TB using TB hemeprint, sensitivity, specificity, PPV, and NPV were 85.4%, 89.6%, 31.1%, and 99.1%, respectively, in primary TB with lower than 6000 WBCs/µL of test set (test set-L). In primary TB with higher than 6000 WBCs/µL of test set (test set-H), those values were 83.1%, 85.6%, 29.7%, and 98.6%, respectively. There were only 0.4% (2/461) and 0.6% (2/326) of normal control samples included in test set-L and -H, respectively. Diagnostic efficiencies except sensitivity in each validation set were very comparable with those in each test set. CONCLUSION: Tuberculosis hemeprint may allow us to screen primary TB with acceptable sensitivity and specificity using combination of TB-specific CPD and calculated parameters.

Set-up uncertainty during breast radiotherapy. Image-guided radiotherapy for patients with initial extensive variation.

PURPOSE: The aim of this work was to establish a customized strategy for image-guided radiotherapy during whole breast irradiation. Risk factors associated with extensive errors were assessed. METHODS AND MATERIALS: A series of 176 consecutive breasts in 174 patients were retrospectively assessed. Electronic portal images from 914 medial and 807 lateral directions were reviewed. On the basis of the chest wall, the deviations between the simulation and each treatment were measured. The systematic (Σ) and random error (σ) of population, and the planning target volume (PTV) margin (2 Σ + 0.7σ) were calculated for each direction. Extensive set-up errors were defined as the fraction over the PTV margins in any direction. For extensive set-up errors, χ(2) tests and logistic regression analyses were conducted. RESULTS: The medial and lateral PTV margins for the right-left, superior-inferior, and anterior-posterior axes and the rotation of collimator were 2.6 and 2.4 mm, 4.6 and 4.6 mm, and 3.1 and 3.3 mm and 2.8 and 2.9 ° and cut-off values for extensive errors were 3, 5, and 4 mm and 3 °, respectively. In χ(2) tests, tumor in upper outer quadrant (p = 0.012) and chest wall thickness ≥ 2.0 cm (p = 0.003) for medial portals and age group (p = 0.036) for lateral portals were associated with extensive errors. In multivariate tests, the extensive error on the initial fraction had a high probability of extensive set-up errors in both medial (OR = 4.26, p < 0.001) and lateral portals (OR = 3.07, p < 0.001). CONCLUSION: In terms of the set-up uncertainty during breast irradiation, patients with extensive error in the initial treatment should be closely observed with serial image-guided radiotherapy.

The glucagon-like peptide-1 receptor agonist exenatide restores impaired pro-islet amyloid polypeptide processing in cultured human islets: implications in type 2 diabetes and islet transplantation.

AIMS/HYPOTHESIS: Islet amyloid, formed by aggregation of human islet amyloid polypeptide (hIAPP), is associated with beta cell death in type 2 diabetes as well as in cultured and transplanted human islets. Impaired prohIAPP processing due to beta cell dysfunction is implicated in hIAPP aggregation. We examined whether the glucagon-like peptide-1 receptor (GLP-1R) agonist exenatide can restore impaired prohIAPP processing and reduce hIAPP aggregation in cultured human islets and preserve beta cell function/mass during culture conditions used in clinical islet transplantation. METHODS: Isolated human islets (n = 10 donors) were cultured with or without exenatide in normal or elevated glucose for 2 or 7 days. Beta cell apoptosis, proliferation, mass, function, cJUN N-terminal kinase (JNK) and protein kinase B (PKB) activation and amyloid formation were assessed. ProhIAPP, its intermediates and mature hIAPP were detected. RESULTS: Exenatide-treated islets had markedly lower JNK and caspase-3 activation and beta cell apoptosis, resulting in higher beta/alpha cell ratio and beta cell area than non-treated cultured islets. Exenatide improved beta cell function, manifested as higher insulin response to glucose and insulin content, compared with non-treated cultured islets. Phospho-PKB immunoreactivity was detectable in exenatide-treated but not untreated cultured islets. Islet culture caused impaired prohIAPP processing with decreased mature hIAPP and increased NH(2)-terminally unprocessed prohIAPP levels resulting in higher release of immature hIAPP. Exenatide restored prohIAPP processing and reduced hIAPP aggregation in cultured islets. CONCLUSIONS/INTERPRETATION: Exenatide treatment enhances survival and function of cultured human islets and restores impaired prohIAPP processing in normal and elevated glucose conditions thereby reducing hIAPP aggregation. GLP-1R agonists may preserve beta cells in conditions associated with islet amyloid formation.

Effect of co-existing copper and calcium on the removal of As(V) by reused aluminum oxides.

Among the various heavy metals, arsenic is frequently found in abandoned mine drainage and the environmental fate of arsenic in real aqueous solutions can be highly dependent on the presence of co-existing ions. In this study, removal of arsenate through adsorption on the reused aluminum oxide or through precipitation was investigated in a single and in a binary system as a function of pH and concentration. Different removal behaviors of arsenate were observed in the presence of different cations as well as a variation of the molar ratios of arsenate to cations. Co-operative effects on arsenate removal by precipitation in solution occurred with an increase of copper concentration, while a decrease of arsenate removal resulted in increasing calcium concentration. It was observed that the arsenate removal in the presence of calcium would be highly dependent on the molar ratios of both elements.

Cellular function of RhoGDI-α mediates the cycling of Rac1 and the regulation of pancreatic beta cell death.

Mycophenolic acid (MPA) is an immunosuppressive agent that is widely used in clinical therapy, including pancreas and islet transplantation. Previously, we showed that MPA induces significant apoptosis of insulin-secreting cells by downregulating RhoGDI-α and increasing JNK expression. In this study, we investigated Rac1 directly associated with RhoGDI-α during MPA-induced apoptosis in INS-1E cells (an insulin-secreting cell line). Cells were treated with MPA for 24 and 36 hours. Immunoprecipitation was used to examine physical interactions between RhoGDI-α and Rac1. Activation and immunoprecipitation assays showed expressions of Rac1 and RhoGDI-α to be directly correlated. Rac1 binding to RhoGDI-α decreased after MPA treatment, and Rac1 was induced and subsequently activated by MPA. We concluded that this novel RhoGDI-α/Rac1/JNK pathway induced apoptosis of transplanted islet cells after MPA treatment.