Maternal Obesity during Pregnancy is Associated with Lower Cortical Thickness in the Neonate Brain

BACKGROUND AND PURPOSE

Recent studies have suggested that maternal obesity during pregnancy is associated with differences in neurodevelopmental outcomes in children. In this study, we aimed to investigate the relationships between maternal obesity during pregnancy and neonatal brain cortical development.

MATERIALS AND METHODS

Forty-four healthy women (28 normal-weight, 16 obese) were prospectively recruited at <10 weeks' gestation, and their healthy full-term neonates (23 boys, 21 girls) underwent brain MR imaging. All pregnant women had their body composition (fat mass percentage) measured at ∼12 weeks of pregnancy. All neonates were scanned at ∼2 weeks of age during natural sleep without sedation, and their 3D T1-weighted images were postprocessed by the new iBEAT2.0 software. Brain MR imaging segmentation and cortical surface reconstruction and parcellation were completed using age-appropriate templates. Mean cortical thickness for 34 regions in each brain hemisphere defined by the UNC Neonatal Cortical Surface Atlas was measured, compared between groups, and correlated with maternal body fat mass percentage, controlled for neonate sex and race, postmenstrual age at MR imaging, maternal age at pregnancy, and the maternal intelligence quotient and education.

RESULTS

Neonates born to obese mothers showed significantly lower (P ≤ .05, false discovery rate-corrected) cortical thickness in the left pars opercularis gyrus, left pars triangularis gyrus, and left rostral middle frontal gyrus. Mean cortical thickness in these frontal lobe regions negatively correlated (R = -0.34, P = .04; R = -0.50, P = .001; and R = -0.42, P = .01; respectively) with the maternal body fat mass percentage measured at early pregnancy.

CONCLUSIONS

Maternal obesity during pregnancy is associated with lower neonate brain cortical thickness in several frontal lobe regions important for language and executive functions.

A Multi-Center Prospective Derivation and Validation of a Clinical Prediction Tool for Severe Clostridium difficile Infection

Background and Aims

Prediction of severe clinical outcomes in Clostridium difficile infection (CDI) is important to inform management decisions for optimum patient care. Currently, treatment recommendations for CDI vary based on disease severity but validated methods to predict severe disease are lacking. The aim of the study was to derive and validate a clinical prediction tool for severe outcomes in CDI.

Methods

A cohort totaling 638 patients with CDI was prospectively studied at three tertiary care clinical sites (Boston, Dublin and Houston). The clinical prediction rule (CPR) was developed by multivariate logistic regression analysis using the Boston cohort and the performance of this model was then evaluated in the combined Houston and Dublin cohorts.

Results

The CPR included the following three binary variables: age ≥ 65 years, peak serum creatinine ≥2 mg/dL and peak peripheral blood leukocyte count of ≥20,000 cells/μL. The Clostridium difficile severity score (CDSS) correctly classified 76.5% (95% CI: 70.87-81.31) and 72.5% (95% CI: 67.52-76.91) of patients in the derivation and validation cohorts, respectively. In the validation cohort, CDSS scores of 0, 1, 2 or 3 were associated with severe clinical outcomes of CDI in 4.7%, 13.8%, 33.3% and 40.0% of cases respectively.

Conclusions

We prospectively derived and validated a clinical prediction rule for severe CDI that is simple, reliable and accurate and can be used to identify high-risk patients most likely to benefit from measures to prevent complications of CDI.

Sampling survey on intellectual disability in 0 approximately 6-year-old children in China

OBJECTIVES

To understand the current status of intellectually disabled children and the prevalence of intellectual disability (ID) in children aged 0 approximately 6 years and its risk factors, and to provide scientific evidence to formulate relevant policies for helping intellectually disabled children.

METHODS

Multiphase, stratified, unequal proportional and cluster sampling was adopted to investigate 60 124 children aged 0 approximately 6 years. All the children investigated were screened for ID using the Denver Developmental Screening Test, and those with positive screening test would be further diagnosed by varied specialists using the Gesell Developmental Inventory.

RESULTS

In total, 560 of 60 124 children were diagnosed as intellectually disabled with an overall prevalence of 0.93%. Prevalence of ID was highest in children living in medium-developed areas with a prevalence of 1.20%, higher than in those living in developed areas (0.75%) and in underdeveloped areas (0.84%). It was higher in rural areas (1.03%) than in urban areas (0.83%), and higher in boys (1.01%) than in girls (0.84%). Prevalence of ID increased with the age of children and decreased with the educational level of their parents.

CONCLUSIONS

The study suggested that ID is still prevalent in the children of China, and rehabilitation for them is lagging behind current needs. Early prevention of ID in children and pre-school education for them should be strengthened.

Clostridium difficile toxin A-induced colonocyte apoptosis involves p53-dependent p21(WAF1/CIP1) induction via p38 mitogen-activated protein kinase

BACKGROUND & AIMS

Clostridium difficile toxin A causes marked apoptosis of colonocytes in vivo and in vitro, which contributes to the formation of ulcers and pseudomembranes. We investigated the role of p53-dependent pathways and p38 mitogen-activated protein kinase (p38) in toxin A-induced colonocyte apoptosis.

METHODS

The effects of the activation of p53 and p53-dependent pathways including p21(WAF1/CIP1) were assessed in nontransformed human colonic NCM460 epithelial cells exposed to toxin A. Phosphorylation of p53 protein by p38 was measured by in vitro kinase assay, whereas p21 induction by activated p53 was determined by gel shift assays and RNA silencing (small interfering RNA). The relationship between colonocyte apoptosis and p38/p53-dependent pathways was studied in intact mice.

RESULTS

Toxin A stimulated p38 and p53 activation and induced cell cycle arrest (G(2)-M) with persistent expression of p21(WAF1/CIP1). Blockage of p38 by SB203580 inhibited p53 phosphorylation and induction of p21(WAF1/CIP1). In intact mice, p38 blockade suppressed toxin A-mediated destruction of intestinal villi, p21(WAF1/CIP1) expression, and enterocyte apoptosis. In addition, toxin A-mediated p21(WAF1/CIP1) and Bak induction, cytochrome c release, and caspase-3 activation were markedly attenuated in p53-silenced colonocytes, despite active p38. Overexpression of p21(WAF1/CIP1) triggered apoptosis and increased toxin A-associated colonocyte apoptosis.

CONCLUSIONS

The signaling pathway for colonocyte apoptosis following toxin A exposure involves p38-dependent activation of p53 and subsequent induction of p21(WAF1/CIP1), resulting in cytochrome c release and caspase-3 activation through Bak induction.

Clostridium difficile toxin B activates the EGF receptor and the ERK/MAP kinase pathway in human colonocytes

BACKGROUND & AIMS

Clostridium difficile toxin B (TxB) mediates acute inflammatory diarrhea characterized by neutrophil infiltration and intestinal mucosal injury. In a xenograft animal model, TxB was shown to induce interleukin (IL)-8 gene expression in human colonic epithelium. However, the precise mechanisms of this TxB response are unknown. The aim of this study was to investigate the TxB-mediated proinflammatory pathway in colonocytes.

METHODS

The effect of TxB on epidermal growth factor receptor (EGFR), extracellular signal-regulated kinase (ERK) 1/2 signaling pathway and IL-8 gene expression was assessed in nontransformed human colonic epithelial NCM460 cells. TxB regulation of EGFR-ERK1/2 signaling pathways was determined using immunoblot analysis, confocal microscopy, and enzyme-linked immunosorbent assay, whereas IL-8 gene expression was measured by luciferase promoter assay.

RESULTS

TxB activates EGFR and ERK1/2 phosphorylation with subsequent release of IL-8 from human colonocytes. Pretreatment with either the EGFR tyrosine kinase inhibitor, AG1478, or an EGFR-neutralizing antibody blocked both TxB-induced EGFR and ERK activation. By using neutralizing antibodies against known ligands of EGFR, we found that the activation of EGFR and ERK1/2 phosphorylation was mediated by transforming growth factor-alpha (TGF-alpha). Inhibition of matrix metalloproteinase (MMP) decreased TGF-alpha secretion and TxB-induced EGFR and ERK activation. Inhibition of MMP, EGFR, and ERK activation significantly decreased TxB-induced IL-8 expression.

CONCLUSIONS

TxB signals acute proinflammatory responses in colonocytes by transactivation of the EGFR and activation of the ERK/MAP kinase pathway.

[The expression of hypoxia inducible factor-1,2 alpha in sporadic clear cell renal cell carcinoma and their relationships to the mutations of von Hippel-Lindau gene]

OBJECTIVE

To evaluate the expression of hypoxia inducible factor (HIF)-1alpha, 2alpha in sporadic clear cell renal cell carcinoma and their relationships to the mutations of von Hippel-Lindau (VHL) gene.

METHODS

Mutations of VHL gene, expression of HIF-1alpha and 2alpha were detected by polymerase chain reaction (PCR), direct DNA sequencing and immunohistochemistry in 77 cases of Chinese sporadic clear cell renal cell carcinoma (CCRCC). The stage was pT(1)N(0)M(0)in 55 patients (71%), pT(2)N(0)M(0) in 7 patients (9%), pT(3)N(0)M(0) in 14 patients (18%), and pT(4)N(0)M(0) in 1 patient (1%). The classification according to the tumor nuclear grading system showed 15 carcinomas (19%) of tumor nuclear grade 1, 56 (73%) of tumor nuclear grade 2 and 6 (8%) of tumor nuclear grade 3.

RESULTS

None of the VHL gene mutations were found in all the normal tissue specimens. VHL gene mutations were detected in 40 (52%) cases of CCRCC. The positive rate of HIF-2alpha (81%) was higher than that of HIF-1alpha (66%) (chi(2) = 23.310, P < 0.01); The positive rate of HIF-1alpha and HIF-2alpha in the cases of mutations (98% and 93% respectively) was higher than that of them in non-mutations (32% and 68% respectively) (chi(2) = 36.386, 7.617, P < 0.01); The correlation between HIF-1alpha and VHL gene mutations was closer than that between HIF-2alpha and VHL gene mutations (partial correlation coefficiency was 4.481 and 2.027 respectively, P < 0.01). The expression of HIF-1alpha and 2alpha in different pathological grade and stage of CCRCC showed no significant difference (P > 0.05).

CONCLUSIONS

Our study suggests that VHL gene mutations are frequent in sporadic CCRCC, and the high expression of HIF-1alpha and 2alpha are found in the group of VHL mutations. However, we have not found significant correlation between the expression of HIF-1alpha and 2alpha and pathological grade and stage of CCRCC in our study.

Clostridium difficile toxin A regulates inducible cyclooxygenase-2 and prostaglandin E2 synthesis in colonocytes via reactive oxygen species and activation of p38 MAPK

Clostridium difficile toxin A induces acute colitis with neutrophil infiltration and up-regulation of numerous pro-inflammatory mediators, but the contribution of cyclooxygenase-2 (COX-2) induction in this infection is unknown. We report here that toxin A induces expression of COX-2 and secretion of prostaglandin E2 (PGE2) in a dose- and time-dependent manner in cultured NCM460 human colonocytes and in human intestinal xenografts. This induction was blocked by SB203580, a p38 MAPK inhibitor, which also decreased the phosphorylation of MSK-1, CREB/ATF-1, and COX-2 promoter activity following toxin A stimulation. Gel shift assays indicated that CREB/ATF-1 was the major proteins binding to the COX-2-CRE. Moreover, colonocytes exposed to toxin A produced reactive oxygen species (ROS), which activated p38 MAPK, MSK-1, and CREB/ATF-1, leading to subsequent COX-2 induction and PGE2 secretion. In intact mice, blockage of p38 MAPK inhibited toxin A-mediated induction of COX-2 in enterocytes as well as lamina propria cells, and significantly blocked the toxin A-induced ileal secretion of fluid and PGE2. Furthermore, a selective COX-2 inhibitor also diminished toxin A-associated ileal fluid and PGE2 secretion. The main signaling pathway for toxin A induction of human COX-2 involves ROS-mediated activation of p38 MAPK, MSK-1, CREB, and ATF-1. Toxin A triggers ileal inflammation and secretion of fluid via COX-2 induction and release of PGE2.

[Analysis of two single nucleotide polymorphisms in von Hippel-Lindau gene and detection of loss of heterozygosity in Chinese sporadic renal cell carcinoma]

OBJECTIVE

To exam two single nucleotide polymorphism(SNP) in VHL gene and intragenic loss of heterozygosity (LOH) of VHL gene in 79 Chinese sporadic renal cell carcinomas(RCCs), and to analyze the relationships between VHL LOH and clinicopathological parameters.

METHODS

The authors extracted tumor and normal tissue DNA and detected two genotypes of intragenic SNP sites, rs779805 in the 5'terminal and rs 1642742 in the 3'terminal of VHL gene by polymerase chain reaction-restriction frament length polymorphism, then analyzed VHL LOH by comparing tumor tissue versus normal tissue in heterozygosities. Subsequently the relationships between VHL LOH and clinicopathological parameters of RCCs were analyzed.

RESULTS

The computed heritage parameters of two SNPs, included genotype frequency, allele frequency, heterozygosity, and polymorphism information content. Twenty-nine heterozygosities were detected in 79 RCCs. LOH was found in 41.4%(12/29) of RCCs. No significant relationships between VHL LOH and age, sex, tumor stage, pathological grade were found.

CONCLUSION

LOH of VHL gene is an important genetic event in Chinese sporadic renal carcinoma, and the LOH frequency is 41.4%. VHL LOH has no influence on stage and grade of RCC.

[Analysis of biallelic inactivation of the von Hippel-Lindau tumor suppressor gene VHL in patients of renal cell carcinoma patient]

OBJECTIVE

To investigate biallelic inactivation of the von Hippel-Lindau tumor suppressor gene (VHL) in patient of renal cell carcinoma (RCC) patient.

METHODS

We extracted tumor and normal DNA from 41 RCC patients. Mutation of VHL gene from tumor tissue was detected from tumor tissue by polymerase chain reaction (PCR) and direct sequencing. Two single nucleotide polymorphism (SNP) sites located in VHL gene were analyzed by PCR restriction fragment length polymorphism, and loss of heterozygosity (LOH) was analyzed for VHL gene by comparing between tumor with normal tissue.

RESULTS

Mutation and LOH of VHL gene was found in 51% (21/41) and 42% (8/19) of RCC patients respectively. LOH was highly associated with mutation positive tumors (r = 0.78) and VHL biallelic inactivation was detected in 37% of RCC patients.

CONCLUSION

Biallelic inactivation of VHL gene occurs in RCC due to VHL mutation and LOH, and its frequency rate is 37%.

[Mutation of von Hippel-Lindau gene and expression of vascular endothelial growth factor in sporadic clear cell renal cell carcinoma and their relationships to angiogenesis]

OBJECTIVE

To evaluate the relationship between the mutation of the von Hippel-Lindau (VHL) gene and expression of vascular endothelial growth factor (VEGF) in sporadic clear cell renal cell carcinoma (CCRCC) and angiogenesis.

METHODS

Polymerase chain reaction (PCR) was used to detect the mutation of VHL gene in the specimens of cancerous tissue and normal tissues away from tumor from 77 patients with CCRCC. Immunohistochemistry was used to examine the expression of VEGF. CD34 staining was used to measure the microvascular density (MVD).

RESULTS

VHL gene mutations were detected in 40 cases (51.9%). The expression rate of VEGF was 79.2% (61 cases). The positive rate of VEGF in the cases with VHL mutation was 92.5%, significantly higher than that in the cases without VHL mutation (64.9%, P = 0.003). The levels of MVD was higher in the cases with VHL mutation and those with VEGF expression were 760.80/mm2 and 715.95/mm2 respectively, both significantly higher than those in the cases without VHL-mutation and those without VEGF expression (547.03/mm2 and 437.44/mm2 respectively, all P = 0.001). The cases with expression of VEGF were divided into two groups according the presence or absence of VHL gene mutations or not. The MVD of the cases with VEGF expression and VHL mutation was 760.80 mm2, significantly higher than that of the cases with VEGF expression and without VHL mutation (547.03 mm2, P = 0.011).

CONCLUSION

The mutation rate of VHL gene is high among the Chinese with sporadic CCRCC. VHL gene mutation increases significantly the VEGF expression, thus, and perhaps via other mechanism too, promoting the angiogenesis in tumor. The high level of MVD of the cases with VHL gene mutation may be related to the high malignant potential of CCRCC.

Metalloproteinases and transforming growth factor-alpha mediate substance P-induced mitogen-activated protein kinase activation and proliferation in human colonocytes

Substance P (SP) participates in acute intestinal inflammation via binding to the G-protein-coupled neurokinin-1 receptor (NK-1R) and release of proinflammatory cytokines from colonic epithelial cells. SP also stimulates cell proliferation, a critical event in tissue healing during chronic colitis, via transactivation of the epidermal growth factor (EGF) receptor (EGFR) and activation of mitogen-activated protein kinase (MAPK). Here we examined the mechanism by which SP induces EGFR and MAPK activation. We used non-transformed human NCM460 colonocytes stably transfected with the human NK-1R (NCM460-NK-1R cells) as well as untransfected U373 MG cells expressing high levels of endogenous NK-1R. Exposure of both cell lines to SP (10(-7) m) stimulated EGFR activation (1 min) followed by extracellular signal-regulated protein kinase (ERK1/2) activation (2-5 min). SP-induced ERK1/2 activation was blocked by pretreatment with the metalloproteinase inhibitor Batimastat/GM6001, the EGFR phosphorylation inhibitor AG1478, and the tumor necrosis factor-alpha-converting enzyme (TACE) inhibitor TAPI-1. Pretreatment with antibodies against potential EGFR ligands suggested that transforming growth factor-alpha (TGFalpha), but not the other EGFR ligands EGF, heparin-binding EGF, or amphiregulin, mediates SP-induced EGFR transactivation. SP stimulated TGFalpha release into the extracellular space that was measurable within 2 min, and this release was inhibited by metalloproteinase inhibitors and the TACE inhibitor TAPI-1. SP also induced MAPK-mediated cell proliferation that was inhibited by TACE, matrix metalloproteinase (MMP), EGFR, and MEK1 inhibitors. Thus, in human colonocytes, NK-1R-induced EGFR and MAPK activation and cell proliferation involve matrix metalloproteinases (most likely TACE) and the release of TGFalpha. These signaling mechanisms may be involved in the protective effects of NK-1R in chronic colitis.

[Somatic mutations of VHL gene and HIF-1alpha expression in primary renal clear cell carcinomas]

OBJECTIVE

To evaluate the significance of somatic mutations of VHL gene and hypoxia-inducible factor-1alpha (HIF-1alpha) expression in primary renal clear cell carcinoma (RCC).

METHODS

Mutation of VHL gene and HIF-1alpha expression were detected by means of PCR, denaturing high-performance liquid chromatography (DHPLC), direct sequencing and immunohistochemistry in 32 samples from primary renal clear cell carcinoma patients.

RESULTS

In 32 RCC samples, 17 samples (53.1%) had and 32 samples of adjacent nonmalignant renal tissue had not mutations of VHL gene expression. Twelve RCC samples (70.6%) which had mutations of VHL gene expressed HIF-1alpha, and it had significant difference to 4 RCC (26.7%) samples which didn't have mutations of VHL gene (P < 0.05).

CONCLUSION

Mutations of VHL gene may play a significant role in the tumorigenesis of RCC, and HIF-1alpha expression correlates with it.

[Vitamin D receptor gene Bsm I polymorphism and the susceptibility to prostate cancer in northern Chinese Han population]

OBJECTIVES

To investigate Bsm I single nucleotide polymorphism (SNP) of vitamin D receptor gene (VDRG) in low-risk Chinese Han population and its relationship to the susceptibility to prostate cancer (PCa), and to discuss the possible reason for the racial difference of PCa.

METHODS

One hundred and three patients with PCa and 106 normal controls, mainly from Northern Chinese Han population, were enrolled in this study. Their blood samples were obtained, all of which were genotyped for Bsm I SNP by denaturing high performance liquid chromatography(DHPLC) methods using case-control study.

RESULTS

The distribution of genotype and allele had no significant difference between PCa patients and normal controls (P > 0.05). The frequencies for the bb, Bb and BB genotypes in PCa patients and normal controls were 92.23%/94.34%, 7.77%/5.66%, and 0/0, respectively. The frequencies for B and b allele were 3.88%, 96.12% and 2.91%, 97.09%, respectively.

CONCLUSIONS

The results indicate no significant relationship between the VDRG polymorphisms and PCa in Northern Chinese Han population. The distribution of VDRG Bsm I SNP varies in different ethnic populations, which may be one reason for the racial difference of PCa.

Identification of the RNA polymerase II subunit hsRPB7 as a novel target of the von Hippel-Lindau protein

Inactivation of the von Hippel-Lindau (VHL) tumor suppressor gene is linked to the hereditary VHL disease and sporadic clear cell renal cell carcinomas (CCRCC). VHL-associated tumors are highly vascularized, a characteristic associated with overproduction of vascular endothelial growth factor (VEGF). The VHL protein (pVHL) is a component of the ubiquitin ligase E3 complex, targeting substrate proteins for ubiquitylation and subsequent proteasomic degradation. Here, we report that the pVHL can directly bind to the human RNA polymerase II seventh subunit (hsRPB7) through its beta-domain, and naturally occurring beta-domain mutations can decrease the binding of pVHL to hsRPB7. Introducing wild-type pVHL into human kidney tumor cell lines carrying endogenous mutant non-functional pVHL facilitates ubiquitylation and proteasomal degradation of hsRPB7, and decreases its nuclear accumulation. pVHL can also suppress hsRPB7-induced VEGF promoter transactivation, mRNA expression and VEGF protein secretion. Together, our results suggest that hsRPB7 is a downstream target of the VHL ubiquitylating complex and pVHL may regulate angiogenesis by targeting hsRPB7 for degradation via the ubiquitylation pathway and preventing VEGF expression.

Overproduction of vascular endothelial growth factor related to von Hippel-Lindau tumor suppressor gene mutations and hypoxia-inducible factor-1 alpha expression in renal cell carcinomas

PURPOSE The von Hippel-Lindau (VHL) tumor suppressor gene is frequently inactivated in the common type of sporadic clear cell renal cell carcinoma (RCC) as well as RCCs associated with VHL disease. The VHL protein targets hypoxia-inducible factor-1 alpha (HIF-1 alpha), a transcription factor that can induce vascular endothelial growth factor (VEGF) expression, for ubiquitination and degradation. Accumulation of HIF-1 alpha caused by mutant VHL protein in tumor cells may result in VEGF over expression, which has been used to explain the increased vascularity of RCC. However, quantitative analyses of VEGF production and its correlation with VHL mutations and HIF-1 alpha expression in authentic tissues from patients with RCC are lacking.

MATERIALS AND METHODS

We analyzed VHL gene mutations by direct DNA sequencing and methylation specific polymerase chain reaction in 31 paired RCC tissue samples. HIF-1 alpha protein expression detected by immunoblotting and immunohistochemical staining, and VEGF protein measured by enzyme-linked immunosorbent assay and immunohistochemical staining were performed using tumor and corresponding normal tissues.

RESULTS

VHL gene mutations were detected in 44% of clear cell RCCs but no differences in methylation patterns in the promoter or exon 1 were found. RCCs with VHL gene mutations or of advanced grade produced significantly higher concentrations of VEGF (p <0.0001). HIF-1 alpha protein expression was found in 40% of clear cell RCCs but 80% of them had VHL mutations (p <0.006). HIF-1 alpha expression correlated directly with higher levels of VEGF production (p <0.0001).

CONCLUSIONS

Our findings indicate that VHL gene alterations and HIF-1 alpha protein expression correlate with a significant increase in VEGF production by RCC. In turn it is associated with a more aggressive tumor phenotype.

The VHL protein recruits a novel KRAB-A domain protein to repress HIF-1alpha transcriptional activity

The von Hippel-Lindau tumor suppressor (pVHL) is a component of an E3 ubiquitin ligase and targets hypoxia-inducible factor-1alpha (HIF-1alpha) for ubiquitylation and degradation under normoxic conditions. pVHL also directly inhibits HIF-1alpha transactivation by recruiting histone deacetylases. Here, we report a novel pVHL-interacting protein that functions as a negative regulator of HIF-1alpha transactivation. This protein, generated from the ZnF197 locus by alternative splicing, contains a Kruppel-associated box (KRAB)-A domain and a SCAN domain, but lacks the 22 C2H2-type zinc fingers present in ZnF197. Therefore, we named this protein pVHL-associated KRAB-A domain-containing protein (VHLaK). We demonstrate that the KRAB-A domain in VHLaK mediates pVHL binding and functions as a transcriptional repression module. The SCAN domain mediates VHLaK homo-oligomerization, which enhances VHLaK repressive activity. pVHL can recruit VHLaK to repress HIF-1alpha transcriptional activity and HIF-1alpha-induced VEGF expression. Finally, we demonstrate that pVHL, VHLaK and KAP1/TIF-1beta can be recruited into a single complex, indicating that KAP1/TIF-1beta may participate in pVHL-mediated transcriptional repression of HIF-1alpha. Our findings provide a novel mechanism for the modulation of HIF-1alpha transactivation by pVHL.

Identification of a deubiquitinating enzyme subfamily as substrates of the von Hippel-Lindau tumor suppressor

The VHL protein (pVHL) is a component of an E3 ubiquitin ligase complex which is involved in the ubiquitination and degradation of the alpha subunits of HIF (hypoxia-inducible factor) in the presence of oxygen. However, it is of considerable interest to identify pVHL substrates other than HIF. In our previous studies, we have shown that VDU1 (pVHL-interacting deubiquitinating enzyme-1) can be ubiquitinated for rapid degradation in a pVHL-dependent manner. In this report we show that another uncharacterized deubiquitinating enzyme, named VDU2 (pVHL-interacting deubiquitinating enzyme-2), is a substrate of pVHL. Based on human and mouse cDNA sequences, VDU1 and VDU2 are identical in approximately 59% of the amino acids with strong homology in the N-terminus and C-terminus and a weaker similarity in the middle region. VDU2 contains the signature motifs of the ubiquitin-specific processing protease family and possesses deubiquitinating activity. Like VDU1, VDU2 interacts with pVHL beta-domain and these two proteins can compete with each other to bind to pVHL. Finally, we demonstrate that VDU2 can also be ubiquitinated and degraded in a pVHL-dependent manner. Based on their amino acid sequence homology and functional interaction with pVHL, VDU1 and VDU2 define a subfamily of ubiquitin specific processing proteases. Since deubiquitination, by reversing ubiquitination, has been recognized as an important regulatory step in ubiquitination-related processes, VDU1 and VDU2 could be important substrates of pVHL E3 ligase complex.

Ubiquitination of a novel deubiquitinating enzyme requires direct binding to von Hippel-Lindau tumor suppressor protein

von Hippel-Lindau (VHL) disease is a hereditary cancer syndrome caused by germline mutations of the VHL gene. Recent studies suggest that VHL protein (pVHL) is a component of an E3 ubiquitin ligase, but the detailed biological function of pVHL remains to be determined. To further elucidate the biological functions of pVHL, we searched pVHL-interacting proteins using yeast two-hybrid screening. A novel protein named VHL-interacting deubiquitinating enzyme 1 (VDU1) was identified as being able to directly interact with pVHL in vitro and in vivo. We have determined the full-length cDNA of this enzyme, which includes two putative subtypes. Type I consists of 942 amino acids, and type II consists of 911 amino acids with predicted molecular masses of 107 and 103 kDa, respectively. We have also cloned a mouse homologue of this enzyme. Sequence analysis reveals that this protein is conserved between human and mouse and contains the signature motifs of the ubiquitin-specific processing protease family. Enzymatic function studies demonstrate its deubiquitinating activity. We have determined that the VDU1-interacting region in pVHL is located in its beta-domain, and several naturally occurring mutations located in this domain disrupt the interaction between pVHL and VDU1 protein. Co-immunoprecipitation demonstrates that VDU1 can be recruited into the pVHL-elongin C-elongin B complex. Finally, we demonstrate that VDU1 is able to be ubiquitinated via a pVHL-dependent pathway for proteasomal degradation, and VHL mutations that disrupt the interaction between VDU1 and pVHL abrogate the ubiquitination of VDU1. Our findings indicate that VDU1, a novel ubiquitin-specific processing protease, is a downstream target for ubiquitination and degradation by pVHL E3 ligase. Targeted degradation of VDU1 by pVHL could be crucial for regulating the ubiquitin-proteasome degradation pathway.

The effects and mechanisms of a novel 2-aminosteroid on murine WEHI-3B leukemia cells in vitro and in vivo

To evaluate the effects of a novel 2-aminosteroid, 2-(4'-methyl-1'-piperazinyl)-3alpha-hydroxyl-5alpha-androstane-17-one (KH), on in vitro murine WEHI-3B leukemia cells, semisolid colony culture, MTT assay, morphological examination, NBT reduction, NSAE test and ACP assay were used to determine proliferation and differentiation. It was found that the growth of leukemia cells in colony and liquid cultures was inhibited by KH (10(-8)-10(-4) mol/l) after treatment for 7 days. The percentages of NBT and NSAE positive cells were 71.17 and 79.25%, respectively, after treatment with KH (10(-8)-10(-6) mol/l) for 5 days. The morphology of treated leukemia cells was identified to be macrophage-like and these cells acquired significant ACP activities. It was indicated that the ACP enzyme activities were increased as high as two and three times of the control, respectively, after treatment with 10(-8) or 10(-5) mol/l KH for 6 days. It was also indicated by DNA fragmentation in gel electrophoresis that WEHI-3B cells were induced toward apoptosis by KH (10(-8)-10(-4) mol/l) when checked at day 5. The c-myc mRNA expressions in WEHI-3B cells were decreased by 58.7% after treatment with KH (10(-8) mol/l) for 5 days. Therefore, it is first reported here that KH, a novel 2-aminosteroid, could suppress proliferation and induce differentiation of WEHI-3B leukemia cells. These differentiated cells were mature macrophage-like cells and showed characteristics of functional phagocytes acquired with acid phosphatase activity. The mechanisms underlying the above effects involved the apoptosis of WEHI-3B leukemia cells and the down-regulation of c-myc oncogene expression. It is also shown that the counts of immature granulocytes and monocytes were significantly decreased in both peripheral blood and bone marrow of BALB/c leukemia mice after KH was administrated per os for 7 consecutive days with four doses (5, 10, 15 or 20 mg/kg day), respectively. It is also observed that the enlarged spleens in leukemia mice were decreased when compared with the control.

[Drug susceptibility testing for M. tuberculosis with proportion method]

OBJECTIVE

To analyze the feasibility of proportion method in drug susceptibility testing (DST) of M. tuberculosis(MTB).

METHODS

DST was performed to 360 strains of MTB using proportion method and absolute concentration method, 30 of them using both China made and Sigma produced anti-TB drugs. MIC was detected in 19 strains whose results were different from standard ones.

RESULTS

In isoniazid (INH) and ethambutol (EMB), the resistance rate and the accordance rate compared with standard results were significantly higher in proportion method than absolute concentration method (P < 0.01). But in streptomycin (SM) and rifampicin (RFP), they did not show any significant difference. The accordance rates of INH, SM, EMB and RFP between two methods were 81.1%, 92.5%, 83.6% and 98.6%. The DST results using China made and Sigma produced anti-TB drugs had no significant difference.

CONCLUSIONS

The main reason made proportion method differ from absolute concentration method is critical concentration of drugs. China made anti-TB drugs are also qualified for DST purpose.