TNF-alpha and IL-6 expression in perfused rat liver after intraportal candidemia vs. E. coli or S. aureus bacteremia.

We tested the hypothesis that regulation of tumor necrosis factor-alpha (TNF-alpha) and IL-6 by the liver differs after intraportal challenge with Candida albicans spp. vs. gram-negative or gram-positive bacteria, independent of microbial clearance kinetics or hepatic O2 consumption (VO2). Buffer-perfused rat livers were infected with equivalent inocula (10(9) colony-forming units) of viable Escherichia coli serotype 055:B5 (EC), exotoxin C-producing Staphylococcus aureus (SA), or two strains of yeast phase C. albicans (CA-1 and CA-2). Microbial clearance and circulating cytokine levels were assessed over 180 min while monitoring VO2 and functional parameters, after which organ-based microbial killing, cell-associated TNF-alpha, and cytokine mRNA levels were determined. Compared with saline controls (normal saline solution; NSS), circulating and cell-associated TNF-alpha and TNF-alpha transcripts minimally increased after CA. In contrast, large increases in perfusate TNF-alpha occurred after EC, peaking at 180 min [135 +/- 32 U/ml (mean + SE)], concomitant with rises in cell-associated cytokine and TNF-alpha transcripts (P < 0.01 vs. NSS). Circulating TNF-alpha also rose after SA but neither cell-associated nor mRNA levels exceeded NSS values. There were no pathogen-specific differences in microbial clearance or VO2. IL-6 gene expression paralleled that for TNF-alpha, but IL-6 bioactivity in perfusates was inhibited by TNF-alpha-dependent and -independent mechanisms. We conclude that hepatic TNF-alpha and IL-6 expression are differentially regulated after taxonomically diverse microbial challenges, with E. coli eliciting the strongest and Candida spp. the weakest stimulatory responses.

Ischemia/reperfusion injury of the ascending colon in ponies: a correlative study utilizing microvascular histopathology and corrosion casting.

Volvulus of the ascending colon (ACV) in the horse results in microvascular injury and necrosis of the intestinal mucosa. This study investigated the site and type of microvascular injury which occurs within the mucosa and submucosa following ACV. Histopathology of volvulus treated ponies demonstrated mucosal necrosis with microvascular hemorrhage and thrombosis. Thrombi occurred within the subepithelial capillaries and edema and hemorrhage developed throughout the mucosa and submucosa. Vascular casts allowed 3-D viewing of samples obtained from the entire pelvic flexure and demonstrated two distinct microvascular changes: 1) disruption of the colonic glandular capillary network occurred concomitantly with the mucosal injury, and 2) extensive endothelial leakage from the submucosal microvasculature contributes to edema formation. Thus, microcorrosion casting of the equine pelvic flexure provided an effective means to characterize the location and severity of vascular leakage and visualize the extent and severity of injury to the capillary network not easily depicted by histopathology. Microvascular casting in conjunction with routine histopathology provided additional information on the pathomorphologic changes in this model of ischemia/reperfusion injury.

TNF-alpha and cyclooxygenase metabolites do not modulate C. albicans septic shock with disseminated candidiasis.

We analyzed differences in host regulation of tumor necrosis factor-alpha (TNF-alpha) production and pathophysiological responses in conscious rats after infection with two strains of pathogenic Candida albicans spp. (CA-1 and CA-2) compared with Escherichia coli serotype 055:B5 (EC). The hypothesis was tested that, in contrast to EC, hypotension, organ injury, and mortality after candidemia are not obligatorily dependent on TNF-alpha or TNF-alpha-induced cyclooxygenase pathway metabolites. Dose, viability, and strain-specific dependencies were established after intravenous 10(6) or 10(9) viable CA, as well as heat-killed (HK) or Formalin-inactivated (FI) CA blastospores, compared with live EC at the 24-h LD25 [10(9) colony-forming units (CFU)] and LD100 (10(10) CFU). Shock without endotoxemia developed 4-8 h after 10(9) live CA-1 or CA-2 (LD100 at 24 h) with disseminated yeast-mycelial transformation and increased microvascular permeability in multiple organs but not after HK or FI CA-1. Peak serum TNF-alpha after an LD100 of CA-1 or CA-2 was < 3% of LD25 EC values and was < 1% of peak values during lethal bacteremia. Similar pathogen-specific differences were found in liver- and lung-associated TNF. Production of functionally inactive TNF-alpha during candidemia was excluded by enzyme-linked immunosorbent assay and sodium dodecyl sulfate-polyacrylamide gel electrophoresis with Western blotting. Passive immunization against TNF-alpha 2 h before microbial challenge was not protective against CA but prevented otherwise lethal EC sepsis. Cyclooxygenase inhibition also failed to attenuate candidemic shock. We conclude that the magnitude and kinetics of TNF-alpha production and TNF-alpha-dependent immunophysiological responses are differentially regulated after lethal fungal vs. gram-negative bacterial infection. Thus TNF-alpha is not a pivotal mediator of the acute Candida septic shock syndrome with disseminated candidiasis.