No abstract

Bronchial epithelial cells (BEC) are the progenitors of bronchogenic carcinomas and are exposed to polycyclic aromatic hydrocarbon (PAH) procarcinogens through inhalation of combustion products. PAH are converted to carcinogenic molecules through a combination of monoxygenation by cytochrome p450 (CYP) enzymes in the presence of NADPH oxidoreductase (OR) and hydrolysis by microsomal epoxide hydrolase (mEH). In artificial systems, the relative expression of these genes determines whether carcinogenic or noncarcinogenic species are generated during metabolism. This relationship was explored in humans by using quantitative competitive reverse transcriptase polymerase chain reaction amplification to determine the range of expression of CYP1A1, CYP1B1, mEH, and NADPH OR in BEC recovered from 10 nonsmokers and 9 smokers. CYP2B7 expression was evaluated because, although little is known of its substrate specificity, it is expressed at high levels in human lung tissue. CYP1A1 and CYP1B1 were expressed in BEC at significantly different levels (P < 0.05) in the 9 smokers at 1.4 +/- 2.3 x 10(4) and 2.4 +/- 3.2 x 10(3) molecules/10(6) beta-actin molecules (mean +/- STD), respectively, but each was measurable in only one of the 10 nonsmokers. There was significant inter-individual variation (P < 0.05) in both CYP1A1 and CYP1B1 expression among the subjects for whom sufficient data were obtained. The inducibility of human BEC CYP1A1 gene by PAH exposure was confirmed in vitro by incubating cultured immortalized human BEC with beta-naphthoflavone and observing a > 6-fold induction of CYP1A1 after 24 h. In contrast to BEC, alveolar macrophages expressed CYP1A1 at low (30-70 molecules/10(6) beta-actin molecules) to unmeasurable levels in both smokers and nonsmokers. There was no significant difference in expression of mEH, CYP2B7, or NADPH OR in smokers compared with nonsmokers. The inter-individual variation in absolute and relative expression of PAH metabolism enzymes in BEC reported here supports the hypothesis that inter-individual variation in ability to activate/inactivate inhaled PAH carcinogens accounts for at least some of the inter-individual variation in risk for bronchogenic carcinoma.

Objective-Arginine deficiency may contribute to microvascular dysfunction, but previous studies suggest that arginine supplementation may be harmful in sepsis. Systemic arginine availability can be estimated by measuring the ratio of arginine to its endogenous inhibitors, asymmetric and symmetric dimethylarginine. We hypothesized that the arginine to dimethylarginine (Arg/DMA) ratio is reduced in patients with severe sepsis and associated with severity of illness and outcomes.Design-Case-control and prospective cohort study This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NIH Public Access Author ManuscriptCrit Care Med. Author manuscript; available in PMC 2012 June 1. Conclusions-The Arg/DMA ratio is associated with severe sepsis, severity of illness, and clinical outcomes. The Arg/DMA ratio may be a useful biomarker, and interventions designed to augment systemic arginine availability in severe sepsis may still be worthy of investigation.

Objective Nitric oxide (NO) deficiency may contribute to microvascular dysfunction in sepsis. Current physiologic paradigms contend that nitrite and/ or S-nitrosohemoglobin (SNOHb) mediate intravascular delivery of NO. These NO metabolites are purportedly consumed during hemoglobin deoxygenation producing NO and coupling intravascular NO delivery with metabolic demand. Systemic nitrite and SNOHb consumption can be assessed by comparing their concentrations in arterial vs. venous blood. We hypothesized that arterial vs. venous (A-V) differences in nitrite and SNOHb are diminished in sepsis and associated with mortality. Design Case-control and prospective cohort study Setting Adult intensive care units of an academic medical center Patients and subjects 87 critically ill septic patients and 52 control subjects Interventions None Measurements and Main Results Nitrite and SNOHb were measured using tri-iodide-based reductive chemiluminescence. In control subjects, arterial plasma, whole blood and red blood cell nitrite levels were higher than the corresponding venous levels. In contrast, SNOHb was higher in venous compared to arterial blood. In septic patients, A-V RBC nitrite and SNOHb differences were absent. Moreover, the plasma nitrite A-V difference was absent in non-survivors. Conclusions In health, nitrite levels are higher in arterial vs. venous blood (suggesting systemic nitrite consumption) whereas SNOHb levels are higher in venous vs. arterial blood (suggesting systemic SNOHb production). These A-V differences are diminished in sepsis, and diminished A-V plasma nitrite differences are associated with mortality. These data suggest pathologic disruption of systemic nitrite utilization in sepsis.