Publications

Vascular endothelial growth factor (VEGF) exerts crucial functions during pathological angiogenesis and normal physiology. We observed increased hematocrit (60-75%) after high-grade inhibition of VEGF by diverse methods, including adenoviral expression of soluble VEGF receptor (VEGFR) ectodomains, recombinant VEGF Trap protein and the VEGFR2-selective antibody DC101. Increased production of red blood cells (erythrocytosis) occurred in both mouse and primate models, and was associated with near-complete neutralization of VEGF corneal micropocket angiogenesis. High-grade inhibition of VEGF induced hepatic synthesis of erythropoietin (Epo, encoded by Epo) >40-fold through a HIF-1alpha-independent mechanism, in parallel with suppression of renal Epo mRNA. Studies using hepatocyte-specific deletion of the Vegfa gene and hepatocyte-endothelial cell cocultures indicated that blockade of VEGF induced hepatic Epo by interfering with homeostatic VEGFR2-dependent paracrine signaling involving interactions between hepatocytes and endothelial cells. These data indicate that VEGF is a previously unsuspected negative regulator of hepatic Epo synthesis and erythropoiesis and suggest that levels of Epo and erythrocytosis could represent noninvasive surrogate markers for stringent blockade of VEGF in vivo.

BACKGROUND

We conducted a study to determine the prevalence and factors associated with hepatic steatosis in human immunodeficiency virus (HIV)-seropositive patients with hepatitis C and to investigate whether steatosis is associated with liver fibrosis.

METHODS

Retrospective chart reviews were conducted in 4 hospitals that serve community-based and incarcerated HIV-infected patients who had undergone a liver biopsy for evaluation of hepatitis C virus (HCV) infection during the period of 2000-2003. Demographic characteristics and medication and laboratory data were collected from the time of the biopsy. A pathologist blinded to all clinical data evaluated the specimens. The primary outcome was presence or absence of steatosis.

RESULTS

Of 260 HIV-HCV-coinfected patients, 183 met inclusion criteria and had a biopsy specimen adequate for review. Steatosis was present in 69% of patients (graded as minimal in 31%, mild in 27%, moderate in 18%, and severe in 1%). Factors associated with steatosis included use of dideoxynucleoside analogues, such as didanosine and stavudine (odds ratio [OR], 4.63; 95% confidence interval [CI], 1.55-13.82). There was a trend toward presence of steatosis and use of other nucleoside analogues or infection with HCV genotype 3 (OR, 2.65 [95% CI, 0.95-7.41] and 3.38 [95% CI, 0.86-13.28], respectively). The presence of steatosis was associated with fibrosis (OR, 1.37; 95% CI, 1.03-1.81).

CONCLUSIONS

In this multiracial population of HIV-HCV-coinfected patients, steatosis was prevalent and was associated with severity of liver fibrosis. Use of nucleoside analogues (particularly didanosine and stavudine) and HCV genotype 3 infection were associated with hepatic steatosis. The development of steatosis is multifactorial in nature and may play a contributory role in the progression of liver disease in HIV-infected patients.

The renin-angiotensin system is implicated in the development of a variety of human diseases. Many studies have sought to characterize the clinical implications of polymorphisms in the angiotensin converting enzyme (ACE) gene. Given the high mortality rate of individuals on chronic hemodialysis (HD), we sought to investigate whether genetic diversity in the ACE gene correlates with mortality in this population. We assembled a racially diverse cohort of prevalent individuals on chronic outpatient HD, and followed it prospectively for a mean of 2.1 years. Subjects were genotyped for seven single nucleotide polymorphisms (SNPs) in the ACE gene. Haplotype probabilities were calculated using an expectation-maximization algorithm. Cox proportional hazards regression was used to determine associations between haplotype and time to mortality from initiation of HD. There was strong linkage disequilibrium (LD) across the ACE gene, with three tagging SNPs found to account for all seven-SNP haplotypes that had a frequency of greater than 4%. After adjustment for age, race, gender, and diabetes status, a three-locus haplotype was associated with a 72% risk reduction in mortality (P = 0.004). The majority of this association was captured by the TT genotype of A-239T promoter polymorphism. The TGG (non-wild-type) haplotype, consisting of three tagging SNPs in the ACE gene, is associated with significantly decreased risk of all-cause mortality in HD patients independent of age, race, gender, and diabetic status. This "protective" haplotype may encompass loci with functional significance in the ACE gene.

Lung endothelial damage is a characteristic morphological feature of ischemia-reperfusion (I/R) injury, although the molecular steps involved in the loss of endothelial integrity are still poorly understood. We tested the hypothesis that the activation of vascular endothelial growth factor (VEGF) cell signaling would be responsible for the increase in lung vascular permeability seen early after the onset of I/R in rats. Furthermore, we hypothesized that the I/R-induced pulmonary edema would be significantly attenuated in rats by the activation of the stress protein response. Pretreatment with Ad Flk-1, an adenovirus encoding for the soluble VEGF receptor type II, prevented I/R-mediated increase in lung vascular permeability in rats. Furthermore, the I/R-induced lung injury was significantly decreased by prior activation of the stress protein response with geldanamycin or pyrrolidine dithiocarbamate. In vitro studies demonstrated that VEGF caused an increase in protein permeability across primary cultures of bovine macro- and microvascular lung endothelial cell monolayers that were associated with a phosphorylation of VE- and E-cadherin and the formation of actin stress fibers. Activation of the stress protein response prevented the VEGF-mediated changes in protein permeability across these cell monolayers and reduced the phosphorylation of VE-and E-cadherins, as well as the formation of actin stress fibers in these cells.