Novel Riboswitch Ligand Analogs as Selective Inhibitors of Guanine-Related Metabolic Pathways

Riboswitches are regulatory elements modulating gene expression in response to specific metabolite binding. It has been recently reported that riboswitch agonists may exhibit antimicrobial properties by binding to the riboswitch domain. Guanine riboswitches are involved in the regulation of transport and biosynthesis of purine metabolites, which are critical for the nucleotides cellular pool. Upon guanine binding, these riboswitches stabilize a 5′-untranslated mRNA structure that causes transcription attenuation of the downstream open reading frame. In principle, any agonistic compound targeting a guanine riboswitch could cause gene repression even when the cell is starved for guanine. Antibiotics binding to riboswitches provide novel antimicrobial compounds that can be rationally designed from riboswitch crystal structures. Using this, we have identified a pyrimidine compound (PC1) binding guanine riboswitches that shows bactericidal activity against a subgroup of bacterial species including well-known nosocomial pathogens. This selective bacterial killing is only achieved when guaA, a gene coding for a GMP synthetase, is under the control of the riboswitch. Among the bacterial strains tested, several clinical strains exhibiting multiple drug resistance were inhibited suggesting that PC1 targets a different metabolic pathway. As a proof of principle, we have used a mouse model to show a direct correlation between the administration of PC1 and the reduction of Staphylococcus aureus infection in mammary glands. This work establishes the possibility of using existing structural knowledge to design novel guanine riboswitch-targeting antibiotics as powerful and selective antimicrobial compounds. Particularly, the finding of this new guanine riboswitch target is crucial as community-acquired bacterial infections have recently started to emerge

Perfusion Fluid Contamination in Relation to Recipient Survival and Acute Cellular Rejection in Orthotopic Liver Transplantation: Retrospective Analysis

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Introduction. A perfusion fluid used in the preservation of a grafted liver represents a medium suitable for microorganism growth. This study investigated the prevalence of perfusion fluid contamination, acute cellular rejection (ACR) episodes, and patient survival rate. Method. This is a retrospective study, based on an electronic database allocating cases of orthotopic liver transplantation. The exclusion criteria were as follows: having been submitted to multiple organ transplantation, liver retransplantation only, and those whose samples had not been collected or sent on the back table procedure or were unobtainable (usually the samples were sent when there was donor infection suspicion/positivity). Our posttransplantation infection prophylactic protocol consisted of ampicillin/sulbactam for 72 hours. The variables in the study were as follows: fluid contamination, presence of acute cellular rejection (ACR, Banff classification), and recipient survival at the first year. Statistical analysis was performed using descriptive statistics and chi-square with Fisher exact test considering significant P < .05. Results. We observed perfusion fluid contamination in 15/121 (12.39%). The agents were as follows: Klebsiella pneumoniae in 6 (4.96%), Staphylococcus epidermidis in 5 (4.13%), and Acinetobacter baumanii in 3 (2.48%) and negative cultures in 106 (87.60%). Only 1 patient had matching for donor infection and positivity hemoculture after the transplantation (K pneumoniae) and he was the only patient associated with fluid infection and death. The recipients who had their fluid preservation with positive cultures had more ACR and the survival rate was similar among those with or without infection. Conclusion. Optimization of microbiological procedures can be performed including fungal and bacterial cultures.43413131315Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Evaluation and comparison of microvessel density using the markers CD34 and CD105 in regenerative nodules, dysplastic nodules and hepatocellular carcinoma

The progression of hepatocellular carcinoma (HCC) is multifactorial and angiogenesis plays a fundamental role, mainly because HCC is a highly vascularized tumor. In this study, we determined microvessel density (MVD) using the immunohistochemical markers, CD34 and CD105 (Endoglin), in 44 hepatectomy specimens, encompassing 44 malignant nodules (HCC), 44 regenerative nodules (RN), and 15 dysplastic nodules (DN). The evaluation included the determination of MVD in all nodules. For statistical analysis, a descriptive analysis was carried out using measurements of position and dispersion for continuous variables; ANOVA was used to compare between groups, considering p < 0.05 as statistically significant. We observed a significant difference when comparing CD34 and CD105 immunoexpression in HCC, DN, and RN. CD105 was predominantly expressed in the peripheral regions in HCC, with mean MVD scores of 6.2 +/- A 4.1 and 10.7 +/- A 4.4 at the center and periphery of the nodules, respectively, with significant differences between groups (p < 0.0001). CD34 had higher mean MVD scores than CD105 in HCC, with a more uniform positivity pattern. CD105 immunoexpression in DN exhibited a pattern similar to HCC. However, in RN, CD105 exhibited a higher MVD score in the central portion of the nodules. CD105 was expressed in a subset of newly formed microvessels in HCC and demonstrated an elevated mean MVD in cirrhotic or regenerative nodules. MVD determined by CD34 and CD105 expression may be used as an additional parameter to distinguish benign from malignant liver nodules.8226026

De novo posttransplantation nonlymphoproliferative malignancies in liver transplant recipients

The risk of developing de novo malignancies after liver transplantation is around 1% per year. The incidence varies from 3% to 15%; it is greater than that in the general population. The potential causes for cancer after solid organ grafting are: chronic immunosuppression and human herpes viral infection. The objective of this paper was to review the medical literature about the subject to verify the incidence of de novo malignancies in our service. We performed retrospective analysis of the medical files of 325 successive patients undergoing orthotopic liver transplantation from September 1991 to December 2006. We analyzed the type of tumor, the risk factors, the treatment modality, and the patient survivals. Recurrences of hepatocellular carcinoma were excluded. There were 5 (1.54%) men of average age 50.2 years, and an 80% mortality rate. Their survival time was affected by the nature of the tumor and by the late manifestations of intestinal obstruction allowing adequate surgical treatment. Four of the patients displayed heavy alcohol and tobacco consumption before transplantation. Screening for premalignant lesions must be strongly encouraged to achieve better postoperative results.39103284328

Prognostic Factors for Hepatocellular Carcinoma Recurrence: Experience With 83 Liver Transplantation Patients

Introduction. Orthotopic liver transplantation (OLT) is a rational therapeutic option for early-stage hepatocellular carcinoma (HCC) providing a potential cure and improving survival. Methods. This retrospective study of a longitudinal cohort used an electronic database collected prospectively from September 1997 to May 2010. The variables were gender, age (years), and alpha-fetoprotein (AFP) level (ng/mL). In explanted livers we observed: microvascular or macrovascular invasion, number of nodules and their largest size, Edmondson-Steiner histological differentiation, incidental tumor transarterial chemoembolization (TACE), Milan criteria, and previous down-staging. Results. Five of 83 (6.0%) subjects including 68 (82%) males with a mean time to diagnosis of 9 months experienced tumor relapses. Mean patient age at HCC recurrence was 55.3 years for male and 44.6 years for female subjects. Vascular invasion was detected in 17/83 (20.5%) subjects, namely 2% of macrovascular invasion, and 52.5% with expanded Milan criteria due to an increased number and size of nodules in the explanted livers. An incidental tumor was observed in 29.5% of cases. Preoperative TACE treatment was performed in 13 (15.6%) patients. None of the patients who had a HCC recurrence had undergone TACE. APP level at the time of recurrence was around 1,900 ng/mL. The predictive factor for mortality was nodule size (P = .04; hazard ratio = 0.0269; confidence interval [CI], 95% 0.0094-0.299). Conclusion. Patients with relapses showed the worst survival and tumor size was a predictive factor for recurrence.4341362136

Red Blood Cell Antigen Alloimmunization in Liver Transplant Recipients

Orthotopic liver transplantation (OLT) is a life-saving procedure for patients with end-stage liver disease. Transfusion support is an important part of OLT. Intraoperative transfusion of large volumes of blood products is recognized to be a poor prognostic factor, probably due to the negative effects of blood transfusions, such as transfusion reactions, infectious contamination of blood products, or immune modulation of the transfused patient. The aim of this study was to evaluate the frequency of alloimmunization and its specificity to red blood cell (RBC) antigens among patients undergoing OLT. We identified 74 RBC alloantibodies in 70 (23%) patients when the indirect antiglobulin test (IAT) was performed. The most common RBC alloantibodies were against Rh system antigens. The majority (41.9%) were directed against the E antigen. Despite the ethnic heterogeneity of our population there were no cases of intravascular hemolysis. The incidence of alloimmunization (23%) was slightly higher among patients than in the literature, most probably as a consequence of our ethnic heterogeneity.42249449