Comparison of various surrogate markers for venous congestion in predicting acute kidney injury following cardiac surgery: A cohort study

BACKGROUND

Venous congestion has been demonstrated to increase the risk of acute kidney injury (AKI) after cardiac surgery. Although many surrogate markers for venous congestion are currently used in clinical settings, there is no consensus on which marker is most effective in predicting AKI.

METHODS

We evaluated various markers of venous congestion, including central venous pressure (CVP), inferior vena cava (IVC) diameter, portal pulsatility fraction (PPF), hepatic vein flow pattern (HVF), intra-renal venous flow pattern (IRVF), and venous excess ultrasound grading score (VExUS) in adult patients undergoing cardiac surgery to compare their ability in predicting AKI.

RESULTS

Among the 230 patients enrolled in our study, 53 (23.0%) developed AKI, and 11 (4.8%) required continuous renal replacement therapy (CRRT). Our multivariate logistic analysis revealed that IRVF, PPF, HVF, and CVP were significantly associated with AKI, with IRVF being the strongest predictor (odds ratio [OR] 2.27; 95% confidence interval [CI], 1.38-3.73). However, we did not observe any association between these markers and CRRT.

CONCLUSION

Venous congestion is associated with AKI after cardiac surgery, but not necessarily with CRRT. Among the markers tested, IRVF exhibits the strongest correlation with AKI.

Hyperoside attenuates carbon tetrachloride-induced hepatic fibrosis via the poly(ADP-ribose)polymerase-1-high mobility group protein 1 pathway

Oxidative stress and inflammation have been implicated in hepatic fibrosis. Antioxidant and anti-inflammatory activities are among the pharmacological effects of hyperoside. This study aimed to evaluate the impact of hyperoside on hepatic fibrosis and elucidate the underlying processes that perpetuate this relationship. The findings indicated that hyperoside significantly protects mouse livers against damage, inflammation, and fibrosis. Specifically, attenuation of hepatic fibrosis is associated with lower expression of HMGB1 protein and reduced expression of Toll-like receptor 4, PARP-1, and nuclear factor-kB (NF-κB) p65 mRNA and protein. Furthermore, hyperoside inhibited the cytoplasmic translocation of HMGB1 and nuclear localization of NF-κB p65 in the hepatic tissues of mice. The results of this study indicate that hyperoside may impose a blocking or reversing effect on hepatic fibrosis; additionally, the corresponding hyperoside-dependent mechanism may be linked to PARP-1-HMGB1 pathway regulation.

Clinical efficacy of targeted therapy, immunotherapy combined with hepatic artery infusion chemotherapy (FOLFOX), and lipiodol embolization in the treatment of unresectable hepatocarcinoma

To evaluate the clinical efficacy of targeted therapy and immunotherapy combined with hepatic arterial infusion chemotherapy (HAIC) of FOLFOX and lipiodol embolization in the treatment of unresectable hepatocellular carcinoma. Patients included in the study were those who received targeted therapy and immunotherapy combined with HAIC of FOLFOX and lipiodol embolization in Zhongshan People's Hospital from December 2020 to June 2021 for unresectable hepatocellular carcinoma. Evaluation indicators included objective response rate (ORR), median progression-free survival (mPFS), median duration of response (mDOR), 1-year overall survival rate (OS), surgical conversion rate, and adverse events. Treatment response was assessed using Response Evaluation Criteria in Solid Tumors (mRECIST and RECIST v1.1). A total of 35 patients were included in this study, 30 of whom completed treatment evaluation. According to mRECIST evaluation criteria, the objective response rate (ORR) was 83.3% (25/30); the complete response (CR) was 60% (18/30); the partial response (PR) was 23.3% (7/30), and stable disease (SD) was 16.7% (5/30). The mDOR was 10.3 months (95% Cl: 8.27-NE), and the mPFS was 13.2 months (95% CI: 10.3-NE); the surgical conversion rate was 30.0% (9/30). The 1-year OS was 96.7%. There were no serious surgical complications and grade 4 or 5 adverse events of targeted therapy, immunotherapy and HAIC. Some patients had grade 3 adverse reactions in gastrointestinal toxicity or hepatotoxicity, and the adverse reactions were improved after corresponding symptomatic treatment. We concluded that HAIC of FOLFOX and lipiodol embolization combined with targeted therapy and immunotherapy had a significant curative effect in the treatment of unresectable hepatocellular carcinoma, with no serious adverse reactions and a high rate of surgical conversion rate.

Standard-dose epirubicin increases the pathological complete response rate in neoadjuvant chemotherapy for breast cancer: a multicenter retrospective study

Background

Neoadjuvant chemotherapy (NAC) has become the best comprehensive treatment choice for breast cancer. Epirubicin is a crucial drug widely used in breast cancer chemotherapy, but it is often used with a reduced dosage in NAC for Chinese patients for its notable cardiotoxicity and frequent adverse events. This study aimed to investigate the efficacy and safety of standard-dose epirubicin in NAC for Chinese breast cancer patients retrospectively.

Methods

We retrospectively collected clinicopathological parameters of breast cancer patients who underwent epirubicin-based NAC and a later surgery from three separate medical centers. Patients were divided into standard-dose and low-dose groups according to the epirubicin dose. The pathological complete response (pCR) rate, as the main therapeutic outcomes, and the incidence of adverse events were recorded and compared.

Results

The pCR rate of the standard-dose group was 41.2%, while the low-dose group was 10.1% (P<0.001). The univariate analysis showed that ER status (HR, 2.519; 95% CI, 1.057-5.988, P=0.037) and epirubicin dose (HR, 6.200; 95% CI, 2.374-16.193, P<0.001) were associated with pCR rates. The multivariate analysis showed that patients receiving standard-dose epirubicin chemotherapy (HR, 6.925; 95% CI, 2.537-18.902, P<0.001) showed more possibility to achieve pCR after NAC. There was no significant difference in the incidence rates of grade III/IV adverse events between these two different dose groups.

Conclusions

Standard-dose epirubicin increases the pCR rate in breast cancer patients treated with NAC, and no other toxicity is noted.

Nanomedicine in lung cancer: Current states of overcoming drug resistance and improving cancer immunotherapy

Lung cancer is considered to cause the most cancer-related deaths worldwide. Due to the deficiency in early-stage diagnostics and local invasion or distant metastasis, the first line of treatment for most patients unsuitable for surgery is chemotherapy, targeted therapy or immunotherapy. Nanocarriers with the function of improving drug solubility, in vivo stability, drug distribution in the body, and sustained and targeted delivery, can effectively improve the effect of drug treatment and reduce toxic and side effects, and have been used in clinical treatment for lung cancer and many types of cancers. Here, we review nanoparticle (NP) formulation for lung cancer treatment including liposomes, polymers, and inorganic NPs via systemic and inhaled administration, and highlight the works of overcoming drug resistance and improving cancer immunotherapy. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Development of a Novel Multiparametric MRI Radiomic Nomogram for Preoperative Evaluation of Early Recurrence in Resectable Pancreatic Cancer

Background

In pancreatic cancer, methods to predict early recurrence (ER) and identify patients at increased risk of relapse are urgently required.

Purpose

To develop a radiomic nomogram based on MR radiomics to stratify patients preoperatively and potentially improve clinical practice.

Study Type

Retrospective.

Population

We enrolled 303 patients from two medical centers. Patients with a disease‐free survival ≤12 months were assigned as the ER group (n = 130). Patients from the first medical center were divided into a training cohort (n = 123) and an internal validation cohort (n = 54). Patients from the second medical center were used as the external independent validation cohort (n = 126).

Field Strength/Sequence

3.0T axial T₁‐weighted (T₁‐w), T₂‐weighted (T₂‐w), contrast‐enhanced T₁‐weighted (CET₁‐w).

Assessment

ER was confirmed via imaging studies as MRI or CT. Risk factors, including clinical stage, CA19‐9, and radiomic‐related features of ER were assessed. In addition, to determine the intra‐ and interobserver reproducibility of radiomic features extraction, the intra‐ and interclass correlation coefficients (ICC) were calculated.

Statistical Tests

The area under the receiver‐operator characteristic (ROC) curve (AUC) was used to evaluate the predictive accuracy of the radiomic signature in both the training and test groups. The results of decision curve analysis (DCA) indicated that the radiomic nomogram achieved the most net benefit.

Results

The AUC values of ER evaluation for the radiomics signature were 0.80 (training cohort), 0.81 (internal validation cohort), and 0.78 (external validation cohort). Multivariate logistic analysis identified the radiomic signature, CA19‐9 level, and clinical stage as independent parameters of ER. A radiomic nomogram was then developed incorporating the CA19‐9 level and clinical stage. The AUC values for ER risk evaluation using the radiomic nomogram were 0.87 (training cohort), 0.88 (internal validation cohort), and 0.85 (external validation cohort).

Data Conclusion

The radiomic nomogram can effectively evaluate ER risks in patients with resectable pancreatic cancer preoperatively, which could potentially improve treatment strategies and facilitate personalized therapy in pancreatic cancer.

Level of Evidence: 4

Technical Efficacy: Stage 4

J. Magn. Reson. Imaging 2020;52:231–245.

The p53/miR-193a/EGFR feedback loop function as a driving force for non-small cell lung carcinoma tumorigenesis

Background

Non-small cell lung carcinoma (NSCLC) is a major worldwide health threat due to its low cure rate and high lethality. Emerging evidence suggests that epidermal growth factor receptor (EGFR) plays vital roles in cancer initiation and progression, and is considered an important cancer-driving protein. However, how EGFR expression is regulated during NSCLC development remains to be fully elucidated.

Methods

In NSCLC clinical samples, EGFR protein levels were measured by western blotting and qRT-PCR, respectively. Combining microRNA (miRNA) target prediction software and the pulldown assay, we predicted microRNAs (miRNAs) that targeted EGFR. Next, three NSCLC cell lines, A549 (p53 WT), H322 (p53 mutant), and H1299 (p53 null), were used to demonstrate the direct targeting of EGFR by miR-193a. In addition, we investigated the biological effects of EGFR inhibition by miR-193a in vitro using Cell Counting Kit-8, 5-Ethynyl-2'-deoxyuridine (EdU), transwell, and apoptosis assays. Then, using ChIP and luciferase assays, we demonstrated that miR-193a was directly activated by p53 at the transcriptional level and that p53-induced-miR-193a and EGFR form a double-negative feedback loop.

Results

We found that EGFR mRNA and protein were upregulated in NSCLC. We predicted that EGFR was a target of miR-193a and validated that miR-193a bound directly to the 3'-UTR of the EGFR mRNA. Moreover, miR-193a inhibited NSCLC proliferation and invasion, and promotes NSCLC apoptosis by directly downregulating EGFR. Then, we demonstrated that p53 directly activated miR-193a transcription, whereas EGFR functioned as a transcriptional repressor to negatively control miR-193a expression, forming a feedback loop. The loop promoted NSCLC cell proliferation and migration and accelerated tumor growth in xenograft mice.

Conclusions

This study highlights a double-negative feedback loop in NSCLC. The feedback loop is crucial because overexpressing EGFR strongly accelerated tumor growth, while miR-193a restoration blocked tumor growth in vivo. Our findings are in line with the emerging opinion that miRNAs and protein regulators form regulatory networks in critical biological processes and that their dysregulation can lead to cellular dysfunction. In conclusion, this study provides important insights into the molecular mechanisms of NSCLC progression and may help inform the development of new therapeutics for managing NSCLC.

Knockdown of AGGF1 inhibits the invasion and migration of gastric cancer via epithelial-mesenchymal transition through Wnt/β-catenin pathway

Background

Angiogenic factor with G-patch and FHA domain 1 (AGGF1), as a newly identified human angiogenic factor, is overexpressed in some types of malignant tumors and closely associated with patient’s prognosis. However, the mechanisms involved in the regulation of AGGF1 in gastric cancer (GC) still remain unclear.

Methods

In this study, AGGF1 level in GC tissues and cell lines was analyzed by western blot and quantitative real-time polymerase chain reaction (qRT-PCR). After knockdown of AGGF expression by RNA interference in GC cell lines MKN-45 and MGC-803, wound healing and transwell assays were conducted to examine the effects of AGGF1 on migration and invasion. Tumor growth was assessed in a mouse xenograft model in vivo. Furthermore, expression levels of epithelial–mesenchymal transition (EMT) biomarkers and involvement of the Wnt/β-catenin pathway were detected by western blot and qRT-PCR.

Results

Compared to those in normal groups, the protein and mRNA of AGGF1 expression levels were significantly higher both in GC tissues and cell lines (all P < 0.05). Knockdown of AGGF1 dramatically inhibited the invasion and migration of MKN-45 and MGC-803 cells (all P < 0.01) in vitro, and suppressed the tumor growth of nude mice xenograft model in vivo. Western blot revealed alterations in EMT biomarkers, suggesting the role of AGGF1 in EMT. Moreover, we found that downregulated expression of AGGF1 attenuated Wnt/β-catenin related protein expression.

Conclusions

Collectively, knockdown of AGGF1 inhibits the invasion and migration of gastric cancer via epithelial–mesenchymal transition through Wnt/β-catenin pathway.

Electronic supplementary material

The online version of this article (10.1186/s12935-019-0765-6) contains supplementary material, which is available to authorized users.

Promoter methylation of p16, Runx3, DAPK and CHFR genes is frequent in gastric carcinoma

Aims and background

Transcriptional silencing induced by hypermethylation of CpG islands in the promoter regions of genes is believed to be an important mechanism of carcinogenesis in human cancers including gastric cancer. A number of reports on methylation of various genes in gastric cancer have been published, but most of these studies focused on cancer tissues or only a single gene. In this study, we determined the promoter hypermethylation status and mRNA expression of 4 genes: p16, Runx3, DAPK and CHFR.

Methods

Methylation-specific polymerase chain reaction (MSP) was used to determine the methylation status of p16, Runx3, DAPK and CHFR gene promoters in cancer and adjacent normal gastric mucosa specimens from 70 patients with gastric cancer, as well as normal gastric biopsy samples from 30 people without cancer serving as controls. In addition, the mRNA expression of p16, Runx3, DAPK and CHFR was investigated in 34 gastric cancer patients by RT-PCR. Bisulfite DNA sequence analysis was applied to check the positive samples detected by MSP.

Results

When carcinoma specimens were compared with adjacent normal gastric mucosa samples, a significant increase in promoter methylation of p16, Runx3, DAPK and CHFR was observed, while all 30 histologically normal gastric specimens were methylation free for all 4 genes. The methylation rate of the 4 genes increased from normal stomach tissue to tumor-adjacent gastric mucosa to gastric cancer tissue. Concurrent methylation in 2 or more genes was found in 22.9% of tumor-adjacent normal gastric mucosa and 75.7% of cancer tissues. No correlation was found between hypermethylation and other clinicopathological parameters such as sex, age, and tumor location. However, the frequency of DAPK and CHFR methylation in cancer tissues was significantly associated with the extent of differentiation and lymph node metastasis (P <0.05) and the frequency of Runx3 methylation was significantly associated with tumor size (P <0.05). Weak expression and loss of expression of the 4 genes was observed in cancer tissues and was significantly associated with promoter hypermethylation (P <0.05).

Conclusions

Promoter hypermethylation of p16, Runx3, DAPK and CHFR is frequent in gastric cancer. DAPK and CHFR promoter hypermethylation may be an important help in evaluating the differentiation grade and lymph node status of gastric cancer. Weak gene expression and loss of gene expression due to promoter hypermethylation may be a cancer-specific event. Free full text available at www.tumorionline.it

A facile and general strategy for the synthesis of porous flowerlike Pt-based nanocrystals as effective electrocatalysts for alcohol oxidation

In this paper, porous flowerlike Pt-based (Pt, PdPt, RhPt and RhPdPt) nanocrystals were successfully achieved by a simple, economic, environmentally friendly route under the same synthetic conditions at 85 °C. The electrocatalytic properties of these flowerlike Pt-based nanocrystals toward alcohols (glycol, glycerol, methanol and ethanol) oxidation were investigated and they displayed enhanced catalytic performance compared with commercial Pt black. Among them, porous Pd45.5Pt54.5 nanoflowers showed the best catalytic performance with significant mass activity and long-term stability. More importantly, the current synthesis strategy can be easily amplified to gram-scale production.

Response of HIV-Infected Patients with Asymptomatic Syphilis to Intensive Intramuscular Therapy with Ceftriaxone or Procaine Penicillin

The objective of this prospective pilot study was to evaluate the response of HIV-infected patients with asymptomatic syphilis to one of two intensive antibiotic treatment regimens. Thirty-one HIV-infected patients with serum rapid plasma reagin titre ≥1:4 and no clinical findings of syphilis were randomized to receive daily intramuscular injections of ceftriaxone or procaine penicillin (plus oral probenecid) for 15 days; 24 returned for follow-up study. Seven of 10 (70%) procaine penicillin-treated patients and 10 of 14 (71%) ceftriaxone-treated patients had a ≥4-fold decline in RPR ( P=0.94); two penicillin-treated and one ceftriaxone-treated patient relapsed. Two patients failed ceftriaxone therapy. Three penicillin-treated, and two ceftriaxone-treated patients were serofast. Serological responses were similar in those patients with and without asymptomatic neurosyphilis. There was no difference in the serologic response to daily treatment with ceftriaxone vs that with procaine penicillin plus probenecid; both treatments were associated with comparatively high rates of serological non-response and relapse.

Value of C-arm computed tomography in radiofrequency ablation of small lung lesions

This study aimed to explore the value of C-arm computed tomography (CT) applications in radiofrequency ablation (RFA) of small lung lesions. The puncture success rate, cumulative survival rate, tumor response rate, complications, and radiation dose during C-arm CT-guided RFA of 36 small lung lesions in 34 patients were analyzed. In 35 RFA procedures for 36 small lung lesions, the puncture success rate was 100%. There were 7 cases of complications, including 4 cases of pneumothorax (puncture suction or closed chest drainage was not required) and 3 cases of hemoptysis. The cumulative survival rate in the 34 patients after RFA was 100% at 6 months, 69.0% at 1 year, and 60.0% at 2 years. In assessments of 36 foci imaged during the follow-up period, the total response rates at 1 month, 3 months, and 6 months were 77.8% (28/36), 69.7% (23/33), and 61.3% (19/31), respectively. The mean cumulative dose and average effective dose during surgery were 120.1 ± 61.4 mGy and 3.5 ± 1.7 mSv, respectively. The application of C-arm CT to RFA of small lung lesions could provide abundant information to the surgeon and increase the lesion puncture success rate and is considered to be a promising image-guided technology.

RhPt flowerlike bimetallic nanocrystals with tunable composition as superior electrocatalysts for methanol oxidation

For the first time, composition-tunable, high-yield, RhPt flowerlike bimetallic nanocrystals were successfully synthesized through an aqueous solution approach. The electrocatalytic activity of these RhPt nanoalloys toward methanol oxidation was investigated and compared to the activity of commercial Pt black and commercial Ru50Pt50/C. The RhPt flowerlike bimetallic nanoallys have shown composition-dependent and superior catalytic properties relative to those of commercial Pt black and commercial Ru50Pt50/C. The peak current density and mass current value of Rh19Pt81 nanoalloys are 0.75 mA cm(-2) and 0.12 mA μg(-1), respectively. For commercial Pt black, they are 0.48 mA cm(-2) and 0.074 mA μg(-1), and for commercial Ru50Pt50/C, they are 0.28 mA cm(-2) and 0.10 mA μg(-1). Moreover, the chronoamperometric measurements show that the RhPt flowerlike nanoalloys have excellent stability over commercial Pt black and commercial Ru50Pt50/C.

One-pot synthesis of Pd–Pt@Pd core–shell nanocrystals with enhanced electrocatalytic activity for formic acid oxidation

Pd–Pt@Pd core–shell nanocrystals were directly synthesized through an aqueous solution approach without any preformed Pd or Pt seeds.

Facile synthesis of PdPt nanoalloys with sub-2.0 nm islands as robust electrocatalysts for methanol oxidation

The high-yield, composition-tunable PdPt nanoalloys with sub-2.0 nm islands were first achieved through a facile aqueous approach.

Effect of 5-Aza-2'-deoxycytidine and trichostatin A on expression and methylation of the Runx3 gene in human gastric carcinoma line SGC-7901

AIM: To evaluate the effect of 5-Aza-2'-deoxy-citydine (5-Aza-dC) and trichostatin A (TSA) on the methylation and expression of the Runx3 gene in human gastric cancer cell line SGC-7901.

METHODS: After cultured SGC-7901 cells were treated with 5-Aza-dC and TSA, the methylation levels of the promoter region of the Runx3 gene were detected by quantitative real-time methylation-specific polymerase chain reaction (QMSP), and Runx3 mRNA and protein expression was detected by reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting, respectively.

RESULTS: Treatment with 5-Aza-dC or TSA alone reduced the methylation levels of the promoter region of the Runx3 gene (70%, 63% vs 100%) and increased Runx3 mRNA (0.29 ± 0.01, 0.28 ± 0.03 vs 0.14 ± 0.03, both P < 0.05) and protein expression levels (0.35 ± 0.02, 0.37 ± 0.02 vs 0.09 ± 0.01, P < 0.05) compared to control cells. Treatment with 5-Aza-dC in combination with TSA could more significantly reduce Runx3 gene promoter methylation levels (37%) and increase Runx3 mRNA (0.45 ± 0.02) and protein expression levels (0.50 ± 0.01) compared to cells treated with 5-Aza-dC or TSA alone (all P < 0.05).

CONCLUSION: 5-Aza-dC and TSA can synergistically reverse Runx3 gene methylation and recover Runx3 mRNA and protein expression in SGC-7901 cells.

Evaluation of steady-state pharmacokinetic interactions between ritonavir-boosted BILR 355, a non-nucleoside reverse transcriptase inhibitor, and lamivudine/zidovudine in healthy subjects

WHAT IS KNOWN AND OBJECTIVE

BILR 355 is a second generation non-nucleoside reverse transcriptase inhibitor. It has shown promising in vitro anti-HIV-1 activities and favourable human pharmacokinetic properties after co-administration with ritonavir (RTV). Lamivudine (3TC) is a nucleoside reverse transcriptase inhibitor. It is excreted predominantly in urine by a transporter-mediated pathway. These two drugs are likely to be given together to HIV-infected patients. The objective of this study was to investigate any steady-state pharmacokinetic interactions between RTV-boosted BILR 355 and 3TC/zidovudine (ZDV).

METHODS

This was a randomized, open label, prospective study. In group A, 39 healthy subjects were given 3TC/ZDV (150 mg/300 mg) twice daily (b.i.d.) for 7 days, and then BILR 355 and RTV (BILR 355/r, 150 mg/100 mg) were co-administered with this regimen for an additional 7 days. Intensive blood samples were taken on days 7 and 14 for pharmacokinetic assessments. In group B, 12 healthy subjects were given BILR 355/r (150 mg/100 mg) b.i.d. for 7 days. The pharmacokinetic data from group B were pooled with data from group B subjects in other similar studies performed in parallel (BILR 355 alone group in BILR 355 drug-drug interaction studies with tipranavir, lopinavir/RTV, and emtricitabine/tenofovir DF; BILR 355 regimen was the same).

RESULTS AND DISCUSSION

After co-administration with BILR 355/r, the AUC(12,ss) and C(max,ss) of 3TC increased by 45% and 24%, respectively; the elimination half-life (t(1/2) ,ss) of 3TC was significantly increased. However, the pharmacokinetics of ZDV was unchanged. Co-administration with 3TC/ZDV resulted in a 22% decrease in AUC(12,ss) and a 20% decrease in C(max,ss) for BILR 355. The observed increase in exposure and prolongation of t(1/2,ss) of 3TC is potentially related to inhibition of OCT-mediated urinary excretion of 3TC.

WHAT IS NEW AND CONCLUSION

Concomitant administration of BILR 355 with 3TC/ZDV resulted in a modest decrease in exposure to BILR 355 and a 45% increase in exposure to 3TC.

Pathobiologic implications of methylation and expression status of Runx3 and CHFR genes in gastric cancer

Runx3 and CHFR genes were defined as tumor suppressor genes in gastric cancer (GC) recently. This paper was to investigate the roles of methylation and expression status of Runx3 and CHFR genes in GC patients. Methylation-specific polymerase chain reaction (MSP) and bisulfite DNA sequencing (BSP) were used to detect methylation status of Runx3 and CHFR genes in GC patients. The expression of Runx3 and CHFR in GC patients was analyzed by reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemical analysis. The expression of the protein and mRNA decreased remarkably in the patients with aberrant promoter methylation of Runx3 and CHFR genes. The methylation status of Runx3 and CHFR were inversely related to the tumor size, tumor invasion depth and tumor differentiation in GC patients. Moreover, the protein expression of Runx3 and CHFR were significantly correlated with tumor invasion depth and tumor differentiation, respectively. Aberrant promoter methylation of Runx3 and CHFR genes may be involved in the carcinogenesis and development of GC and may provide useful clues for the prediction of the malignant behaviors of GC.

Use of the Zung depression scale in patients with traumatic brain injury: 1 year post-injury

OBJECTIVE

The purpose of this study was to examine if the physical disabilities of patients with traumatic brain injury (TBI) would influence the assessment of depression when using the Zung depression scale.

METHOD

Patients with TBI (n=59) were assessed 1 year after injury for depression by both a psychiatrist and the use of the Zung depression scale.

RESULTS

By psychiatric evaluation, seven of 17 (41%) patients with severe TBI and one of 20 (5%) of the patients with moderate TBI were diagnosed with major depressive disorder. With the Zung depression scale, 10 of 17 (59%) patients with severe TBI met the cut-off (scored >55) for depression, whereas none of the patients with moderate (n=20) or mild (n=22) TBI did. The mean (SD) scores of the somatic scale were 2.91 (0.93), 2.49 (0.92) and 1.25 (0.43) for each group. The mean scores of the affective scale were 2.58 (0.90), 1.85 (0.79) and 1.24 (0.46). For patients with moderate (p<0.05) and severe (p<0.10) TBI, scores on the somatic items exceeded scores on their affective items. No difference in somatic and affective scale scores was noted for the patients with mild TBI.

CONCLUSION

The increased endorsement of somatic results may be the somatic difficulties associated with traumatic brain injury.

Thalidomide: dermatological indications, mechanisms of action and side-effects

Thalidomide was first introduced in the 1950s as a sedative but was quickly removed from the market after it was linked to cases of severe birth defects. However, it has since made a remarkable comeback for the U.S. Food and Drug Administration-approved use in the treatment of erythema nodosum leprosum. Further, it has shown its effectiveness in unresponsive dermatological conditions such as actinic prurigo, adult Langerhans cell histiocytosis, aphthous stomatitis, Behçet's syndrome, graft-versus-host disease, cutaneous sarcoidosis, erythema multiforme, Jessner-Kanof lymphocytic infiltration of the skin, Kaposi sarcoma, lichen planus, lupus erythematosus, melanoma, prurigo nodularis, pyoderma gangrenosum and uraemic pruritus. This article reviews the history, pharmacology, mechanism of action, clinical uses and adverse effects of thalidomide.

Pitfalls of molecular replacement: the structure determination of an immunoglobulin light-chain dimer

The structure of protein Cle, a human light-chain dimer from the lambdaIII subgroup, was determined using 2.6 A data; the R value is 18.4%. The structure was solved, after a false start, by molecular replacement with the lambdaII/V Mcg protein as a search structure. When the refinement did not proceed beyond an R value of 27%, it was discovered that while the constant domains were in their correct positions in the unit cell, the incorrect variable domains were used for defining the molecule. The correct solution required a rotation of 180 degrees around the local twofold axis that relates the two constant domains of the dimer. The correct variable domain positions overlap about 70% of the same volume as the incorrect ones of a symmetry-related molecule. The refinement distorted the geometries of the domains. Though the constant domains were in their correct positions, the r.m.s. (root-mean-square) deviation of the Calpha atom position was 1.2 A when the two constant domains were compared. For the correct structure, this value is 0.5 A. The phi and psi angles, the r.m.s. chiral value and the free R value, even when calculated a posteriori, were good indicators of the correctness of the structure. The quaternary structure of the Cle molecule is similar to that in Mcg (crystallized from ammonium sulfate); the elbow bend is 115 degrees. However, the arrangement of the variable domains differs from that observed in other variable domain dimers. The variable domains of Cle are 0.7 A closer than in Mcg or variable dimer Rei. The hydrogen bonding at the interface of the two domains is novel. Residues Tyr36 from both monomers form a hydrogen bond that is part of a network with the Gln89 residues from both monomers. For the first time hydrogen bonds were observed between the main-chain peptide N and O atoms of the complementarity-determining region CDR2 and CDR3 segments of both monomers.

Emergence of trimethoprim-resistant Escherichia coli in healthy persons in the absence of prophylactic or therapeutic antibiotics during travel to Guadalajara, Mexico

Thirty-nine healthy US students without diarrheal disease and who had not received prophylactic or therapeutic antibiotics were monitored for emergence of trimethoprim-resistant gram-negative fecal flora for a 3-week period after arrival in Guadalajara, Mexico. During this time period, most students showed no change in total fecal gram-negative bacteria (p > 0.05) but showed an increasing level of trimethoprim (TMP) resistance (p < 0.01) among fecal coliforms. Escherichia coli was the TMP-resistant organism isolated in 18 of 39 (46%) healthy students. These 18 TMP-resistant E. coli were also resistant to ampicillin (44%), azithromycin (11%), chloramphenicol (39%), ciprofloxacin (11%), doxycycline (89%), erythromycin (100%), furazolidone (72%), levofloxacin (17%), trimethoprim-sulfamethoxazole (89%) and trovafloxacin (17%). In the absence of prophylactic and therapeutic antibiotics, increased acquisition of TMP-resistant gram-negative fecal flora in this developing country is probably due to poor sanitary conditions and the recurrent and heavy exposure to antimicrobial-resistant indigenous flora as a result of contaminated food and drink.

Increased fecal IgE among infants in a rural community of Egypt: an analysis of associated risk factors

Newborns in rural Bilbeis, Egypt were followed to 1-year of age to document the incidence and risk factors associated with the development of fecal IgE. Factors associated with increased fecal IgE included infants aged 3-6 months (relative risk (RR) = 3.28, 95 per cent confidence intervals (CI) = 1.03-13.60, p < 0.05) and mother being vaccinated antenatally (RR = 2.17, CI - 1.01-4.61, p < 0.05). Decreased fecal IgE was observed with consumption of rice (RR = 0.37, CI = 0.12-0.94, p < 0.05), biscuits (RR = 0.43, CI = 0.15-0.99, p < 0.05), potatoes (RR = 0.39, CI = 0.11-0.98, p < 0.05), and fruits and vegetables (RR = 0.20, CI = 0.02-0.80, p < 0.05). After multivariate adjustment, increased risk was observed with consumption of milk pudding (RR = 7.48, CI = 1.54-36.20, p < 0.05) and wet-nursed infants (RR = 2.77, CI = 1.17-6.54, p < 0.05). Infants who were completely breastfed (RR = 0.13, CI = 0.02-0.68, p < 0.05) and infants' family owning a television set (RR = 0.29, CI = 0.12-0.67, p < 0.05) were less likely to develop fecal IgE. Our findings indicate that prelacteal feeding with certain foods, early supplementation of breastfeeding, and sociodemographic factors are associated with increased fecal IgE.

Sociodemographic, environmental and clinical risk factors for developing persistent diarrhoea among infants in a rural community of Egypt

The study documents the incidence of persistent diarrhoea and its sociodemographic, household, environmental and clinical risk factors. One hundred and fifty-two newborns were followed for the first 12 months of life in Bilbeis, Egypt. The household of each participant was surveyed at baseline and was visited twice a week. The study infants experienced persistent diarrhoea at a rate of 0.51 episode/case per year. Development of persistent diarrhoea was associated with water storage in mud-containers (Odds ratio [OR] = 4.36, confidence interval [CI] 1.4-14.8), pump-water supply (OR = 3.5, CI 1.2-10.2), and absence of a latrine in the household (OR = 2.74, CI 1.01-7.38). Detection of faecal IgE (OR = 3.32, CI 1.0-10.9) and high stool frequency (OR = 2.95, CI 1.1-7.8) appeared as important clinical predictors for the onset of persistent diarrhoea. The incidence of persistent diarrhoea among young infants in Bilbeis, Egypt, was high. Sociodemographic, environmental and clinical parameters were important risk factors for the development of persistent diarrhoea.

Impact of breast-feeding on Giardia lamblia infections in Bilbeis, Egypt

A total of 152 infants were followed from birth to 1 year of age in a rural community of Egypt to document Giardia lamblia infection and to determine the effect of breast-feeding on enteric infections by this protozoan. Asymptomatic Giardia infections persisted as long as 4 months, with a mean duration of excretion of 7.18 weeks. The incidence of asymptomatic infection was 4.5 episodes per child-year. Exclusively breast-fed infants had lower risk for asymptomatic (odds ratio [OR] = 0.66, 95% confidence interval [CI] = 0.45-0.96, P < 0.05) and symptomatic infections (relative risk [RR] = 0.50, 95% CI = 0.27-0.90, P < 0.05). Furthermore, breast-fed infants had fewer clinical manifestations, including mucus in stool (23.8% versus 76.2%, P = 0.08), loss of appetite (17.6% versus 82.3%, P < 0.05), and abdominal tenderness (17% versus 82.9%, P < 0.05) compared with infants who were not exclusively breast-fed. Breast-feeding should be considered as an effective means to prevent Giardia infections and should be encouraged in regions where G. lambia is highly endemic.

X-ray crystal structure of proto-oncogene product c-Rel bound to the CD28 response element of IL-2

BACKGROUND

The proto-oncogene product c-Rel is a Rel/NF-kappaB family transcription factor that plays a critical role in lymphoid cell development and mediates CD28-induced expression of interleukin 2 (IL-2). The CD28 response element (CD28RE) in the IL-2 enhancer is nonameric and similar to the kappaB DNA target sites recognized by p65 homodimers.

RESULTS

We have determined and refined the X-ray crystal structure of the c-Rel homodimer complexed to the CD28RE DNA site, 5'-AGAAATTCC-3', to 2.85 A resolution. The c-Rel homodimer binds CD28RE in a mode similar to that observed in the p65/IL-8 kappaB crystallographic complex. Binding studies reveal that the c-Rel homodimer recognizes the CD28RE with higher affinity as compared to other canonical kappaB sequences despite the nonconsensus A:T base pair at the 5' end of the CD28RE. Preferential recognition of the CD28RE by c-Rel results from the direct contacts between the protein and the DNA as well as intrasubunit interactions between the beta(f)-beta(g) loop in the dimerization domain and the DNA-contacting loop L1 of the N-terminal domain. Not only do these loops have different conformations in other Rel/DNA crystallographic complexes, but they also contain two of the five oncogenic point mutations found in v-Rel.

CONCLUSIONS

The current structure indicates that a non-DNA-contacting loop in the dimerization domain and the DNA-contacting loop L1 may play critical roles in defining affinity and specificity. Two amino acid changes in these segments may account for the differential DNA binding by v-Rel as compared to that of c-Rel.

Human methadone self-administration: effects of diazepam pretreatment

The effect of diazepam on methadone self-administration was examined. Five methadone-maintained patients with a history of benzodiazepine abuse were recruited. Patients were stabilized on 80 mg of methadone per day. After stabilization patients participated in methadone self-administration sessions. During each session, 128 presses (fixed ratio 128) of 1 button delivered 10 ml of 0.054 mg/ml methadone solution. The same number of button presses on a 2nd button delivered 10 ml of vehicle. Forty-five min prior to the self-administration session, 0 (placebo), 5, 10, or 20 mg per 70 kg body weight diazepam was administered. Ratings of drug liking, goodness, strength, and high were collected 5, 30, 60, 90, and 150 min after the end of the self-administration session. Diazepam pretreatment significantly decreased the amount of methadone consumed. The 10- and 20-mg diazepam doses significantly increased reports of good, like, strong, and high.

Major leg wound complications after saphenous vein harvest for coronary revascularization

BACKGROUND

Major leg wound complications after coronary artery bypass graft procedures are infrequent and few are reported in the literature. We present our experience in treating 23 patients with major leg wound complications after coronary revascularization procedures.

METHODS

A retrospective review of 3,525 bypass procedures with saphenous vein grafts performed over a 10-year period was conducted. Ten potential risk factors for those who developed major leg wound complications were analyzed and compared with the entire cohort of patients undergoing similar bypass procedures during the same period.

RESULTS

Lower extremity wound complications occurred in 145 patients (4.1%), 23 of whom (0.65%) required additional surgical interventions (62 total). There were 32 wound debridements, 8 skin grafts, 11 vascular procedures, 5 amputations, 3 fasciotomies, 2 free tissue transfers, and 1 fasciocutaneous flap. Of ten variables evaluated by multivariate analysis, female gender, peripheral vascular disease, and postoperative intraaortic balloon pump use were identified as significant independent predictors of major leg wound complications (p < 0.0001).

CONCLUSIONS

The causes of major leg wound complications after saphenous vein harvest for coronary artery bypass graft procedures are multifactorial. To minimize these complications, we recommend vascular evaluations before saphenous vein harvest, attention to proper surgical technique, and careful harvest site selection.

Laboratory measurement of aggression in high school age athletes: provocation in a nonsporting context

This study investigated the relationship between aggression and type of sports involvement in high school age boys. Athletes (16 boys), ages 15 to 18 years, were separated into two groups, one of 8 athletes who participated in sports with high physical contact, e.g., football and basketball, and the other of 8 athletes who participated in low contact sports, e.g., track and baseball. Students participated in six 25-min. Point Subtraction Aggression Paradigm sessions. The paradigm is an established laboratory model of aggression with three response options: (1) a point-maintained response, (2) an aggressive response, and (3) an escape response. Analysis indicated that the only difference between the groups was that individuals who participated in high contact sports emitted significantly more aggressive responses than individuals who participated in low contact sports. Similarly, psychometric measures of aggression indicated that individuals in the former group self-reported more behavioral incidents of aggression than those in the latter group.

Intrathoracic application of the reverse latissimus dorsi muscle flap

The use of the reverse latissimus dorsi muscle flap based on its paraspinous perforators for posterior trunk wound coverage has been described previously. However, few studies have reported its intrathoracic application. In this study the authors present their experience in treating 3 patients with various intrathoracic defects using the reverse latissimus dorsi muscle flap. There were 1 male and 2 female patients who ranged in age from 4 to 74 years (mean, 49 years). The etiology included an infected aortic graft, a bronchopleural fistula, and a recurrent congenital diaphragmatic hernia. Follow-up ranged from 2 to 24 months. Successful outcomes were achieved in all 3 patients, and there was no recurrence or wound complication identified. Their results demonstrate the versatility and reliability of the reverse latissimus dorsi muscle flap in treating low posterior intrathoracic defects.

An unusual presentation of constriction band syndrome

Congenital constriction band syndrome is a rare entity with a wide spectrum of associated congenital anomalies. Review of the pathogenesis and an unusual case of constriction band syndrome in a newborn are presented. Surgical excision of the deformity and the band was performed within the first week of life. There were no vascular or neural structures within the excised tissue, and there were no other associated anomalies other than dextrocardia and an equinovarus deformity of the foot. The wound was closed primarily without the need for Z-plasties. This alternative method of treatment can be considered in such unusual locations of constriction band syndromes.

Characterization of the dimer interface of transcription factor NFkappaB p50 homodimer

Dimers of the Rel/NFkappaB transcription factor family form with differential stabilities through the combinatorial association of five polypeptides: p50, p52, p65, cRel, and RelB. Here, we have characterized the nature of the monomer-dimer equilibrium of the p50 homodimer. Sedimentation equilibrium studies show that the equilibrium constant for p50 dimer dissociation is in the low micromolar range. Using the X-ray crystal structure of the p50 homodimer as a guide, we have created site-directed alanine mutations at ten dimer-forming residues in p50 and measured their effects on p50 homodimerization. Characterization of these alanine mutants by a series of chemical crosslinking, size-exclusion chromatography, and sedimentation equilibrium experiments shows that the most critical residue in stabilizing the p50 dimer interface is Y267. Sedimentation equilibrium experiments show that an alanine substitution at position 267 destabilizes the dimer interface by 2.0 kcal/mol. Alanine substitutions at two other positions, L269 and V310, significantly destabilize the p50 dimer interface. These two residues are observed to mediate critical interactions in the crystal structure. Together, these three residues constitute the "hot-spot" of protein-protein interaction in p50 dimerization. Of the four charged residues in the dimer interface, R252, D254, E265, and D302, only D302 contributes significantly to p50 dimer stability. D254 appears to slightly destabilize the subunit interface. Although residues H304, R305, and F307 occupy positions at the hydrophobic core of the interface and appear to be involved in multiple interactions in the X-ray crystal structure, alanine substitutions at these positions do not significantly reduce the affinity for p50 dimerization. Upon evaluating the roles of these amino acid residues at the p50 dimer interface, we propose that differential contributions of a few key residues dictate the selectivity of dimer formation within the Rel/NFkappaB family.

Construction, expression, purification and functional analysis of recombinant NFkappaB p50/p65 heterodimer

NFkappaB plays an important role in mediating the gene expression of numerous cellular processes such as growth, development, the inflammatory response and virus proliferation. The p50/p65 heterodimer is the most abundant form of the NFkappaB dimers and plays a more elaborate role in gene regulation. Biochemical research on p50/p65 NFkappaB has not benefited however from the availability of easily purified recombinant protein. We report two methods for the large scale expression and purification of recombinant NFkappaB p50/p65 heterodimer. The first utilizes a bacterial double expression vector which contains two ribosomal binding sites to facilitate the coexpression of the polypeptides in the p50/p65 NFkappaB heterodimer. The second method uses a mixed protein refolding strategy. Both methods yield crystallizable protein. Electrophoretic mobility shift assays confirm that the DNA binding affinity is independent of the method used to purify the protein. These methods will facilitate the numerous studies on various NFkappaB/Rel family members.

Reconstructive surgery in children after meningococcal purpura fulminans

BACKGROUND/PURPOSE

Purpura fulminans (PF) is a serious, often life-threatening disease. As more children are surviving their disease, surgeons are presented with increasing numbers of multiple and complicated wounds as sequelae of PF. The purpose of this paper is to review the management of nine cases of PF, and present the reconstruction method in treating bilateral exposed elbow and knee joints.

METHODS

All cases of pediatric patients with PF and treated by the division of plastic and reconstructive surgery between 1986 and 1998 were reviewed.

RESULTS

Seven children (78%) had meningococcal PF, and one (11%) had PF after Haemophilus influenza septicemia. PF developed in one (11%) but with no growth in either blood or cerebrospinal fluid cultures. Five children (56%) required amputation procedures. Two children (22%) required knee disarticulation. Two patients (22%) had free myocutaneous flap transfers for bone coverage. One (11%) had PF involving the face.

CONCLUSIONS

Meningococcal PF is a rare, often life-threatening disease generally of childhood. More children are surviving their diseases but with devastating sequelae. Successful reconstructive treatment outcome of these children requires a multidisciplinary team approach involving multiple specialties. The goal is to preserve function, maintain maximal length, and salvage limbs when possible. Flexibility and innovation are necessary in treating these multiple and complicated wounds.

The use of tissue expanders in staged abdominal wall reconstruction

Reconstruction of large abdominal wall defects not amenable to primary closure remains a challenging problem. Various reconstructive techniques have been described in the surgical literature each with its advantages and disadvantages. In this report the authors describe their experience in treating 11 patients with large abdominal wall defects utilizing prosthetic mesh in conjunction with tissue expanders. Between 1986 and 1997 there were 6 pediatric and 5 adult patients treated with this method. The etiology included three congenital omphaloceles, five cases of necrotizing fasciitis, and three gunshot wounds. All patients initially required insertion of prosthetic mesh to bridge their large abdominal wall defects. This was followed by staged abdominal wall reconstruction with tissue expanders and prosthetic mesh. None of the patients had mesh infection or extrusion, and none developed enteric fistula or recurrent hernia. The tissue expansion process was well tolerated by all patients. One patient had partial exposure of the tissue expander due to thinning of the expanded skin. Our results suggest that the use of tissue expanders provides reliable, well-vascularized soft-tissue coverage and minimizes potential mesh-related complications in abdominal wall reconstruction.

The crystal structure of the IkappaBalpha/NF-kappaB complex reveals mechanisms of NF-kappaB inactivation

IkappaBalpha regulates the transcription factor NF-kappaB through the formation of stable IkappaBalpha/NF-kappaB complexes. Prior to induction, IkappaBalpha retains NF-kappaB in the cytoplasm until the NF-kappaB activation signal is received. After activation, NF-kappaB is removed from gene promoters through association with nuclear IkappaBalpha, restoring the preinduction state. The 2.3 A crystal structure of IkappaBalpha in complex with the NF-kappaB p50/p65 heterodimer reveals mechanisms of these inhibitory activities. The presence of IkappaBalpha allows large en bloc movement of the NF-kappaB p65 subunit amino-terminal domain. This conformational change induces allosteric inhibition of NF-kappaB DNA binding. Amino acid residues immediately preceding the nuclear localization signals of both NF-kappaB p50 and p65 subunits are tethered to the IkappaBalpha amino-terminal ankyrin repeats, impeding NF-kappaB from nuclear import machinery recognition.

A domain flip as a result of a single amino-acid substitution

BACKGROUND

The self-assembly properties of beta domains are important features of diverse classes of proteins that include cell-adhesion molecules, surface receptors and the immunoglobulin superfamily. Immunoglobulin light-chain variable domains are well suited to the study of structural factors that determine dimerization, including how residues at the interface influence the preferred dimer arrangement.

RESULTS

Single-site mutants of light-chain variable domain Len, designated LenQ38E and LenK30T, formed 'flipped' dimers in which one domain was rotated by about 180 degrees compared with the native protein. The dimer in the native protein is similar to that found between variable domains in Fab immunoglobulin fragments. When compared to the native dimer, more surface area is buried, and more hydrogen bonds and salt bridges are formed between the monomers in the flipped conformation.

CONCLUSIONS

Immunoglobulin light-chain variable domains can form a minimum of two distinct quaternary structures. Single-site mutations resulting from changes of one base, such as the exchange of Gln38 to Glu or Lys30 to Thr, change the 'conventional' dimer of protein Len to a flipped arrangement. Native Len is not found in the flipped-domain dimer conformation because it would have excess positive electrostatic potential at the dimer interface that is not compensated by other forces. Excess negative or positive electrostatic potential at the dimer interface can have a determining effect on the mode of dimerization.

Crystal structure of p50/p65 heterodimer of transcription factor NF-kappaB bound to DNA

The NF-kappaB p50/p65 heterodimer is the classical member of the Rel family of transcription factors which regulate diverse cellular functions such as immune response, cell growth, and development. Other mammalian Rel family members, including the proteins p52, proto-oncoprotein c-Rel, and RelB, all have amino-terminal Rel-homology regions (RHRs). The RHR is responsible for the dimerization, DNA binding and cytosolic localization of these proteins by virtue of complex formation with inhibitor kappaB proteins. Signal-induced removal of kappaB inhibitors allows translocation of dimers to the cell nucleus and transcriptional regulation of kappaB DNA-containing genes. NF-kappaB specifically recognizes kappaB DNA elements with a consensus sequence of 5'-GGGRNYYYCC-3' (R is an unspecified purine; Y is an unspecified pyrimidine; and N is any nucleotide). Here we report the crystal structure at 2.9 A resolution of the p50/p65 heterodimer bound to the kappaB DNA of the intronic enhancer of the immunoglobulin light-chain gene. Our structure reveals a 5-base-pair 5' subsite for p50, and a 4-base-pair 3' subsite for p65. This structure indicates why the p50/p65 heterodimer interface is stronger than that of either homodimer. A comparison of this structure with those of other Rel dimers reveals that both subunits adopt variable conformations in a DNA-sequence-dependent manner. Our results explain the different behaviour of the p50/p65 heterodimer with heterologous promoters.

Variable domain structure of kappaIV human light chain Len: high homology to the murine light chain McPC603

Antibody light chains of the kappa subgroup are the predominant light chain component in human immune responses and are used almost exclusively in the antibody repertoire of mice. Human kappa light chains comprise four subgroups. To date, all crystallographic studies of human kappa light chains were carried out on proteins of the kappaI subgroup. The light chain produced by multiple myeloma patient Len. was of the kappaIV subgroup, it differed by only one residue from the germ-line gene encoded protein. The variable domain fragment of the light chain was crystallized from ammonium sulfate in space group C222(1). The crystal structure was determined by molecular replacement and refined at 1.95 A resolution to an R-factor of 0.15. Protein Len has six additional residues in its CDR1 segment compared to the kappaI proteins previously characterized. The kappaIV variable domain, Len, differs in only 23 of 113 residues from murine kappa light chain McPC603. The RMS deviation upon superimposing their alpha-carbons was 0.69 A. The CDR1 segment of the human and murine variable domains have the same length and conformation although their amino acid sequences differ in 5 out of 17 residues. Structural features were identified that could account for the significantly higher stability of the human kappaIV protein relative to its murine counterpart. This human kappaIV light chain structure is the closest human homolog to a murine light chain and can be expected to facilitate detailed structural comparisons necessary for effective humanization of murine antibodies.

The role of DNA in the mechanism of NFkappaB dimer formation: crystal structures of the dimerization domains of the p50 and p65 subunits

BACKGROUND

Members of the rel/NFkappaB family of transcription factors play a vital role in the regulation of rapid cellular responses, such as those required to fight infection or react to cellular stress. Members of this family of proteins form homo- and heterodimers with differing affinities for dimerization. They share a structural motif known as the rel homology region (RHR), the C-terminal one third of which mediates protein dimerization. Crystal structures of the rel/NFkappaB family members p50 and p65 in their DNA-bound homodimeric form have been solved. These structures showed that the residues from the dimerization domains of both p50 and p65 participate in DNA binding and that the DNA-protein and protein dimerization surfaces form one continuous overlapping interface. We desired to investigate the contribution of DNA to NFkappaB dimerization and to identify the mechanism for the selective association of rel/NFkappaB family peptides into transcriptionally active dimers.

RESULTS

We report here the crystal structures of the dimerization domains of murine p50 and p65 at 2.2 A and 2.0 A resolution, respectively. A comparison of these two structures suggests that conservative amino acid changes at three positions are responsible for the differences in their dimer interfaces. The presence of the target DNA does not change the dimer interface of either protein in any significant manner.

CONCLUSIONS

These two structures suggest that the rel/NFkappaB family of transcription factors use only a few conservative changes in their amino acid sequences to form a host of dimers with varying affinities for dimerization. Amino acids at positions corresponding to 254, 267, and 307 of murine p50, function as primary determinants for the observed differences in dimerization affinity. The DNA-contacting charged amino acid sidechains from the dimerization domains are held in a similar conformation in both the DNA-bound and free states, therefore, no major structural rearrangement is required to bring these residues into contact with the DNA.

Molecular modeling of immunoglobulin light chains implicates hydrophobic residues in non-amyloid light chain deposition disease

Light chain deposition disease is a severe complication of certain immunoproliferative disorders, due to the secretion of a monoclonal light chain which precipitates close to basement membranes of several tissues. A kappa isotype restriction and an unusual frequency of a variable region subgroup (VkappaIV) suggest that precise structural features govern the propensity of pathogenic light chains to precipitate in extracellular spaces. We studied primary structures of light chains from six patients with light chain deposition disease in comparison with light chains from other pathological conditions. Sequence alignment revealed the presence of certain amino acids only in light chain deposition disease, in particular non-polar replacing hydrophilic residues. To determine the role of these residues, structures of the variable domain from four kappa chains belonging to VkappaI and VkappaIV subgroups responsible for deposition disease were modeled using known immunoglobulins as templates. The most evident structural features shared by all pathogenic light chains were hydrophobic residues exposed to the solvent in complementarity determining regions 1 or 3. In contrast to immunoglobulin light chain-related amyloidosis, where deposition of organized material might be due to electrostatic interactions between light chain dimers, hydrophobic interactions could enhance amorphous precipitation in non-amyloid light chain deposition disease.