Merging models of hepatitis C virus pathogenesis

Chronic hepatitis C virus (HCV) infection is one of the major causes for development of liver cirrhosis and end-stage liver disease. This article reviews two contrasting models of HCV pathogenesis, discusses the merits of each, and presents a rationale for combining the two models into one. Any successful model of HCV pathogenesis must explain how the characteristic features of cirrhosis and end-stage liver disease arise. These features include the loss of hepatocyte function (low serum albumin and reduced clotting ability); the presence of regenerative nodules; and the deposition of excessive extracellular matrix material, especially collagen (fibrosis), which is associated with the transformation of the liver sinusoids to capillary-like structures leading to portal hypertension. A successful model should explain several observations about the rate of disease progression. HCV is characterized by slow progression of fibrogenesis and, importantly, cirrhosis seems to develop only after a long latency (and only in a subset of patients). Among the prognostic factors of disease progression, the age at infection with the HCV virus and the presence of fibrosis appear to be highly relevant in predicting the development of progressive fibrosis. Traditional models of HCV pathogenesis propose that fibrogenesis is the predominant process. Fibrogenesis is induced by activation of fibrogenic cells, such as stellate cells, which results in excessive collagen deposition. By altering the normal architecture and vasculature, the collagen bands finally lead to cirrhosis and loss of organ function. Activation of stellate cells is induced by inflammation, cytokine signaling, and possibly by hepatocyte apoptosis. The telomere model of HCV pathogenesis suggests that hepatocyte damage plays an essential role in the development of cirrhosis. According to this model, hepatocyte damage leads to increased cell turnover, and to the accelerated shortening of hepatocyte telomeres. Critical telomere shortening leads to hepatocyte senescence, loss of hepatocyte function, exhaustion of hepatocellular regeneration, and to a greatly enhanced fibrotic response to injury. This review summarizes both models and presents evidence that these models are not mutually exclusive but rather can be merged into a comprehensive pathogenesis model that outlines the pathway of HCV-induced cirrhosis.     

Smoking Impairs Rectal Mucosal Bloodflow—A Pilot Study: Possible Implications for Transanal Advancement Flap Repair

ABSTRACT Transanal advancement flap repair has been advocated as the treatment of choice for transsphincteric perianal fistulas, because it enables the healing of almost all fistulas without sphincter damage and consequent continence disturbance. After initial promising reports, recently less favorable results have been reported. It remains unclear why there is such a large variety in the reported healing rates. Recently, it has been suggested that impaired wound healing caused by a diminished rectal mucosal perfusion in patients who smoke may lead to the breakdown of the advancement flap in patients undergoing flap repair for perianal fistulas. This study was designed to investigate the difference in blood flow in rectal mucosa between patients who smoke and those who do not smoke. Furthermore, we assessed the impact of the creation of a mucosa advancement flap and the difference in blood flow in the flap between smoking and nonsmoking patients. Between July 2001 and July 2002, 23 consecutive patients (19 males; median age, 46 (range, 26–69) years) with a perianal fistula of cryptoglandular origin underwent surgery for a perianal fistula. Among them were 13 patients who smoked cigarettes. All patients underwent intraoperative laser Doppler flowmetry. Median blood flow before transanal advancement flap repair was 35 (range, 8–70) volts in patients who did not smoke. In patients who smoked the median blood flow before transanal advancement flap repair was 18 (range, 7–35) volts. Blood flow was significantly lower in patients who smoked (P = 0.018; Mann-Whitney). In conclusion, it seems likely that impaired wound healing caused by a diminished rectal mucosal perfusion is a contributing factor in the breakdown of advancement flaps in patients who smoke cigarettes.Read at the meeting of The American Society of Colon and Rectal Surgeons, New Orleans, Louisiana, June 21 to 26, 2003.Reprints are not available.     

Early-onset sarcoidosis and CARD15 mutations with constitutive nuclear factor-kappaB activation: common genetic etiology with Blau syndrome

Early-onset sarcoidosis (EOS) and inheritable Blau syndrome (BS) share characteristic clinical features of juvenile-onset systemic granulomatosis syndrome that mainly affects skin, joints, and eyes. However, no direct evidence has been shown for the possible common origin of these 2 diseases. Recent discovery of CARD15 mutations in BS families encouraged us to investigate similar CARD15 mutations in EOS patients. Among 10 EOS cases retrospectively collected in Japan, heterozygous missense mutations were found in 9 cases; 4 showed a 1000C>T (R334W in amino acid change) that has been reported in BS, 4 showed novel 1487A>T (H496L), 1538T>C (M513T), 1813A>C (T605P), and 2010C>A (N670K), and 1 case showed double 1146C>G (D382E)/1834G>A (A612T) mutations on different alleles. All 6 of these variants of CARD15 showed increased basal nuclear factor (NF)-kappaB activity. These findings indicate that the majority of EOS and BS cases share the common genetic etiology of CARD15 mutations that cause constitutive NF-kappaB activation.     

Characterization of the sensitizing potential of chemicals by in vitro analysis of dendritic cell activation and skin penetration

Development of in vitro models to identify sensitizing chemicals receives public interest since animal testing should be avoided whenever possible. In this article we analyze two essential properties of sensitizing chemicals: skin penetration and dendritic cell (DC) activation. Activation of immature DC derived from peripheral blood monocytes was evaluated by flow cytometric analysis of CD86 positive cells and quantitative measurement of interleukin-1beta and aquaporin P3 gene expression. The sensitizer 2,4,6-trinitrobenzenesulfonic acid induced a concentration-dependent response for all parameters, whereas the irritant sodium lauryl sulfate did not. When two related aromatic amines, p-toluylenediamine (PTD) and hydroxyethyl-p-phenylenediamine (HE-PPD) were tested, both induced substantial DC activation indicating their potential sensitizing properties. These findings contrasted with in vivo results: in murine local lymph node assays (LLNA) PTD, but not HE-PPD, was sensitizing using acetone/aqua/olive oil as vehicle. Skin penetration measurement revealed that this was due to bioavailability differences. On retesting HE-PPD in the LLNA using the penetration enhancer dimethylsulfoxide as vehicle, it induced a specific response. We conclude that in vitro analysis of DC activation capability of the two selected chemicals demonstrates that prediction of skin sensitization potential is possible provided that skin penetration data indicate sufficient bioavailability of the test compound.     

Wirtsbereichsverhalten der Bakteriophagen T3 und T7 an Escherichia coli K12-Stämmen

The closely related phages T3 and T7 exhibit different growth patterns on Escherichia coli W host cells (E. coli K12 derivatives). T7 grows normally while T3 does not adsorb. T3h_w mutants displaying a T7-like host range were isolated and described.     

Marker chromosome genomic structure and temporal origin implicate a chromoanasynthesis event in a family with pleiotropic psychiatric phenotypes

Small supernumerary marker chromosomes (sSMC) are chromosomal fragments difficult to characterize genomically. Here, we detail a proband with schizoaffective disorder and a mother with bipolar disorder with psychotic features who present with a marker chromosome that segregates with disease. We explored the architecture of this marker and investigated its temporal origin. Array comparative genomic hybridization (aCGH) analysis revealed three duplications and three triplications that spanned the short arm of chromosome 9, suggestive of a chromoanasynthesis‐like event. Segregation of marker genotypes, phased using sSMC mosaicism in the mother, provided evidence that it was generated during a germline‐level event in the proband's maternal grandmother. Whole‐genome sequencing (WGS) was performed to resolve the structure and junctions of the chromosomal fragments, revealing further complexities. While structural variations have been previously associated with neuropsychiatric disorders and marker chromosomes, here we detail the precise architecture, human life‐cycle genesis, and propose a DNA replicative/repair mechanism underlying formation.     

The LDLR locus in Alzheimer's disease: a family-based study and meta-analysis of case-control data

Genetic linkage studies suggest the presence of an Alzheimer's disease (AD) risk gene on chromosome 19, acting independently of apolipoprotein E (apoE), a known AD risk factor on 19q13. The low density lipoprotein receptor (LDLR) is an interesting candidate because it maps within the linked interval, and is intimately involved in cholesterol homeostasis and the function of apoE. We tested three previously reported single nucleotide polymorphisms (SNPs) within LDLR in a large sample of discordant sibships from multiplex AD families, and failed to find evidence for genetic association with disease risk. In addition, we performed meta-analyses for SNP rs5925 on published data from five independent case control samples, but did not detect any significant summary odds ratios. Based on our data, it seems unlikely that these genetic variants in LDLR make a significant contribution to AD risk in the general population.     

LSECtin interacts with filovirus glycoproteins and the spike protein of SARS coronavirus

Cellular attachment factors like the C-type lectins DC-SIGN and DC-SIGNR (collectively referred to as DC-SIGN/R) can augment viral infection and might promote viral dissemination in and between hosts. The lectin LSECtin is encoded in the same chromosomal locus as DC-SIGN/R and is coexpressed with DC-SIGNR on sinusoidal endothelial cells in liver and lymphnodes. Here, we show that LSECtin enhances infection driven by filovirus glycoproteins (GP) and the S protein of SARS coronavirus, but does not interact with human immunodeficiency virus type-1 and hepatitis C virus envelope proteins. Ligand binding to LSECtin was inhibited by EGTA but not by mannan, suggesting that LSECtin unlike DC-SIGN/R does not recognize high-mannose glycans on viral GPs. Finally, we demonstrate that LSECtin is N-linked glycosylated and that glycosylation is required for cell surface expression. In summary, we identified LSECtin as an attachment factor that in conjunction with DC-SIGNR might concentrate viral pathogens in liver and lymph nodes.