Sequence variation of bradykinin receptors B1 and B2 and association with hypertension

OBJECTIVE: To identify variants in the complete genomic sequence of the two subtypes of bradykinin receptors: B1 (BDKRB1) and B2 (BDKRB2) and to examine the association of these variants with essential hypertension. DESIGN: A case-control design comparing hypertensive and normotensive individuals was used. METHOD: A 64.4 kb genomic region containing the BDKRB1 and BDKRB2 genes was sequenced in 30 African-American individuals. A total of 282 single-nucleotide polymorphisms (SNPs) were identified. A total of 21 SNPs were genotyped in our complete cohorts of hypertensive and normotensive African-Americans (n = 218), American-Caucasians (n = 220) and Greek-Caucasians (n = 194). Pair-wise correlation coefficients were computed to assess linkage disequilibrium (LD) patterns among the SNPs. Chi-squared tests and logistic regression were used to assess association between the SNPs and hypertension status. RESULT: Pairwise LD demonstrated a general pattern of decline with increasing distance, which was consistent among the three groups with less LD in African-Americans. One SNP in the promoter region of BDKRB2 (rs1799722) was associated with hypertension (P = 0.044) in African-Americans. One SNP in BDKRB2 and three SNPs in BDKRB1 were associated with hypertension (P-values between 0.026 and 0.0004) in American-Caucasians. Haplotypes including those four SNPs and one SNP in B2, which results in an amino acid change, demonstrated a significant haplotype frequency difference between hypertensive and normotensive American-Caucasians (P = 0.025). CONCLUSION: These results support the hypothesis that the African-American population is an older population compared with the other samples and the two bradykinin receptors may play a role in blood pressure regulation.     

Septic arthritis due to Salmonella enteritidis associated with infliximab use

A unique case of septic arthritis caused by Salmonella enteritidis in a patient receiving infliximab for rheumatoid arthritis is presented. Antimicrobial chemotherapy with surgical intervention was necessary for eradication of the infection. Physicians should be aware of rare manifestations of Salmonella infections associated with infliximab use, especially in endemic areas.     

The impact of third-generation beta-blocker antihypertensive treatment on endothelial function and the prothrombotic state: effects of smoking

BACKGROUND: The significance of beta-blockers in the treatment of cardiovascular diseases is well established. The effect of vasodilating beta-blockers on endothelial function and prothrombotic state has not been investigated. METHODS: The study comprised 550 consecutive patients with uncomplicated essential hypertension. They were treated with celiprolol, carvedilol or nebivolol monotherapy (171, 179, and 200 patients, respectively), achieving comparable blood pressure reduction. Plasma levels of fibrinogen and homocystine and serum levels of plasminogen activator inhibitor-1 (PAI-1) were obtained before and 6 months after initiation of treatment. RESULTS: The three drugs differentiated in regard to homocystine (P <.00001) and fibrinogen level changes (P =.00003), but not (P = NS) in PAI-1 change. In smokers, differentiation was found in all three parameters (P =.0002, P =.001, and P =.006 for fibrinogen, PAI-1, and homocystine, respectively), but in nonsmokers differentiation was found only in homocystine change (P =.00003). In smokers, fibrinogen, PAI-1, and homocystine were reduced more (P =.002, P =.0009, and P <.0001, respectively) than in nonsmokers in the whole study cohort. The effect of nebivolol was more prominent in smokers than nonsmokers in reducing all three parameters (P =.0001,.003, and.003, respectively), whereas in celiprolol and carvedilol-treated groups, differentiation between smokers and nonsmokers was significant (P =.00003 and.01, respectively) only in homocystine level change. CONCLUSIONS: In hypertensive smokers, nebivolol resulted in a significant decrease of plasma PAI-1, fibrinogen and homocystine. Celiprolol also significantly affected these parameters but to a lesser degree, whereas carvedilol had no significant favorable action. In nonsmokers, homocystine was reduced significantly by nebivolol. We conclude that smoking status should be a determinant of antihypertensive treatment choice.     

ICAM-1, ICAM-2 and ICAM-3 in the Sera of Patients with Idiopathic Pulmonary Fibrosis

In order to test the serum levels of ICAM-1, ICAM-2 and ICAM-3 in patients with idiopathic pulmonary fibrosis (IPF), twenty patients with IPF and eleven with secondary interstitial fibrosis (SIF), as well as forty healthy volunteers (HV) were studied. Serum intracellular adhesion molecules (ICAM) 1, 2 and 3 were assessed by ELISA. Functional respiratory tests, which included spirometry and lung diffusing capacity were simultaneously performed. Median values of serum ICAM-1 and ICAM-2 were higher in the patients' than in the healthy volunteers' (HV) group: IPF group: 946.60 ng/ml and 400.14 ng/ml; SIF group: 901.58 ng/ml and 378.27 ng/ml; HV group: 308.40 ng/ml and 217.55 ng/ml, respectively (p < 0.05). ICAM-3 serum levels were equal between the three groups. ICAM-2 negatively correlated to DLCO values. (p < 0.005). It can be concluded that ICAM 1 and 2 are elevated in the sera of patients with pulmonary fibrosis. ICAM-2 might be associated with a more impaired clinical status.     

Melanoma invasion in reconstructed human skin is influenced by skin cells – investigation of the role of proteolytic enzymes

Melanoma invasion is a complex multi stage process involving changes to the cell/extracellular matrix (ECM) and cell/cell interactions. We have previously shown using an in vitro model of reconstructed human skin (consisting of human dermis with a basement membrane [BM] and populated with human skin cells) that some melanoma cells (HBL cell line) invade more actively in the presence of adjacent normal skin cells. The aim of the present study was to further investigate the relationship between melanoma cells, skin cells and ECM proteins during melanoma cell invasion through reconstructed skin, extending this to a study of three melanoma cell lines. We also examined whether such cell/cell induced invasion is due to increased expression and activation of matrix-metalloproteinase-2 (MMP-2) and MMP-9, or due to increases in general protease activity for keratinocytes, fibroblasts or melanoma lines. Addition of skin cells dramatically altered the invasive behaviour of the three metastatic melanoma cell lines (HBL, C8161 and A375SM) used; they increased the invasive ability of HBLs which were unable to invade on their own; they potentiated the invasion of C8161 cells which were invasive in their own right, but reduced the invasion of A375-SM cells which were aggressive invaders in the absence of skin cells. Latent forms of MMP-2, and MMP-9, were clearly expressed by the normal skin cells whereas all three melanoma lines weakly expressed these proteases. Fibroblast and keratinocyte MMPs were activated specifically by culture on type I collagen and on dermis which retained an intact basement membrane. These findings demonstrate that while there is an active communication between melanoma cells and adjacent skin cells, the invasive process is dictated by the melanoma cells and not the skin cells. However, activation of skin cell derived MMPs may play an important role in facilitating invasion by particular melanoma phenotypes. This revised version was published online in July 2006 with corrections to the Cover Date.     

Allele-specific collateral and fitness effects determine the dynamics of fluoroquinolone resistance evolution

Collateral sensitivity (CS), which arises when resistance to one antibiotic increases sensitivity toward other antibiotics, offers treatment opportunities to constrain or reverse the evolution of antibiotic resistance. The applicability of CS-informed treatments remains uncertain, in part because we lack an understanding of the generality of CS effects for different resistance mutations, singly or in combination. Here, we address this issue in the gram-positive pathogen Streptococcus pneumoniae by measuring collateral and fitness effects of clinically relevant gyrA and parC alleles and their combinations that confer resistance to fluoroquinolones. We integrated these results in a mathematical model that allowed us to evaluate how different in silico combination treatments impact the dynamics of resistance evolution. We identified common and conserved CS effects of different gyrA and parC alleles; however, the spectrum of collateral effects was unique for each allele or allelic pair. This indicated that allelic identity can impact the evolutionary dynamics of resistance evolution during monotreatment and combination treatment. Our model simulations, which included the experimentally derived antibiotic susceptibilities and fitness effects, and antibiotic-specific pharmacodynamics revealed that both collateral and fitness effects impact the population dynamics of resistance evolution. Overall, we provide evidence that allelic identity and interactions can have a pronounced impact on collateral effects to different antibiotics and suggest that these need to be considered in models examining CS-based therapies.

Antibiotics are a cornerstone of the prevention and treatment of bacterial infections; however, their efficacy is rapidly declining due to the emergence and spread of antibiotic resistance (1). Advances in antibiotic discovery and design have not kept pace with resistance evolution (2), necessitating experimentally validated treatment strategies (3). Selection inversion, a strategy that aims to circumvent the emergence and dissemination of antibiotic resistance by combining existing antibiotics based on their physiological and/or evolutionary interactions, has recently gained prominence (4). Among these, collateral sensitivity (CS)-informed strategies are particularly promising (5).CS occurs when mutations conferring resistance to one antibiotic increase sensitivity toward other antibiotics in the same or different functional class (6). Because of this effective trade-off, bacteria treated with a pair of drugs exhibiting reciprocal CS are unable to simultaneously evolve resistance to both agents (4). Recent studies have examined the frequency and mechanisms of CS, although these have been largely restricted to laboratory strains of a small number of bacterial species (5, 7–14). In addition, none of these studies have examined if collateral effects are conserved for different clinically circulating resistance alleles to the same antibiotics. This is especially relevant given that resistance to any given antibiotic can arise from mutations in different genes or at different sites within a gene (15). Because these resistance alleles cause distinct phenotypic effects, both with respect to changes in minimum inhibitory concentration (MIC) and bacterial fitness (16), they may also underlie a distinct spectrum of collateral effects, only some of which would be suitable for CS-informed therapies. To address this limitation, we examine collateral responses to distinct genes and alleles that confer resistance to fluoroquinolones (FQs) in the Gram-positive pathogen Streptococcus pneumoniae.S. pneumoniae invasive infections are responsible for the most deaths among vaccine-preventable diseases globally (17). FQs are a mainstay of treatment against invasive pneumococcal disease (18), but successful FQ treatment is threatened by the emergence of FQ-resistant strains, which have been reported to be as high as 10.5% (19). De novo FQ resistance in S. pneumoniae arises predominantly via the stepwise accumulation of chromosomal mutations in the quinolone resistance-determining regions (QRDRs) of the DNA gyrase (gyrA) and/or topoisomerase IV (parC) genes (19). Mutations in either gyrA or parC result in low-level FQ resistance, whereas the combination of mutations in both genes results in high-level resistance, often affecting multiple agents within the class (18, 20). Alleles carrying different mutations in QRDR regions, in pneumococci and other species, have varying impacts on FQ resistance and on the fitness of strains carrying them (21, 22); these effects are believed to influence the population frequencies of different alleles during monotherapy (23). If similar phenotypic heterogeneity exists for collateral responses, this could impact the efficacy of CS-based combination therapies and the persistence and spread of FQ resistance.Here, we studied collateral effects of FQ resistance by generating S. pneumoniae mutant strains via allelic replacement that encode clinically relevant FQ resistance mutations in gyrA and parC (19). These mutants were used to assess how different alleles conferring resistance to the same antibiotic influence the susceptibility to other antibiotics and whether interactions between these alleles modulate their collateral effects. We then developed and applied a mathematical model to quantitatively study the population dynamics of resistance evolution during different antibiotic combination treatment regimes.