Inflammatory cell availability affects ozone-induced lung damage.

Identifying whether or not neutrophils have a role to play in the early stages of acute lung epithelial injury brought about by inhalation of reactive substances continues to be a major area of investigation. In this study, the availability of circulating neutrophils was manipulated by treatment with either cyclophosphamide or rabbit antiserum against rat neutrophils, prior to exposures to air, a single high ozone exposure of 1 or 2 ppm for 3 h, or a continuous exposure to 0.8-1.0 ppm for up to 48 h. Although cyclophosphamide treatment resulted in undetectable levels of neutrophils in the blood, the recovery of tissue marginated-interstitial neutrophils of 1 x 10(6) cells by collagenase tissue digestion was not significantly diminished at the onset of air and ozone exposures. Cyclophosphamide treatment alone did not cause any permeability damage to air-exposed rat lungs, but did ameliorate ozone-induced increases in bronchoalveolar lavage (BAL) neutrophil and albumin recoveries after both short-term and 1 d of continuous ozone exposure. In contrast to cyclophosphamide, antiserum treatment resulted in greater than a 90% decrease in neutrophil recoveries from both blood and lung tissue at the onset of air and ozone exposures. Antiserum treatment also abrogated ozone-induced neutrophil accumulations in lung lavageable spaces following both single and continuous ozone exposures, but did not significantly affect ozone-associated lung permeability damage indicated by unaltered BAL fluid albumin recoveries. These data demonstrated that under experimental conditions when neutrophils remain within lung tissue marginated and interstitial pools, reduction in circulating blood neutrophil availability is associated with a concomitant decrease in ozone-induced lung damage.

Mechanism of heme oxygenase-1 gene activation by cadmium in MCF-7 mammary epithelial cells. Role of p38 kinase and Nrf2 transcription factor.

The mouse heme oxygenase-1 (HO-1) gene, ho-1, contains two inducible enhancers, E1 and E2. Of several cell lines tested, induction of an E1/luciferase fusion construct, pE1-luc, by CdCl(2) is most pronounced in MCF-7 cells. In these cells, E1, but not E2, is necessary and sufficient for ho-1 gene activation. Exposure of MCF-7 cells to 10 micrometer CdCl(2) stimulates phosphorylation of ERK, JNK, and p38 mitogen-activated protein kinases, implicating one or more of these signaling pathways in ho-1 gene induction. SB203580, an inhibitor of p38, diminishes cadmium-stimulated pE1-luc expression and HO-1 mRNA levels by up to 70-80%. PD098059, an ERK pathway inhibitor, does not affect HO-1 mRNA induction at the highest concentration (40 micrometer) tested. Similarly, co-expression of a dominant-negative mutant of p38alpha, but not of ERK1, ERK2, JNK1, or JNK2, reduces basal and cadmium-induced pE1-luc activity. E1 contains binding sites for the activator protein-1 (Fos/Jun), Cap'n'Collar/basic leucine zipper (CNC-bZIP), and CCAAT/enhancer-binding protein (C/EBP) families of transcription factors. A dominant-negative mutant of Nrf2 (a CNC-bZIP member), but not of c-Jun or C/EBPbeta, inhibits pE1-luc activation by cadmium. Induction of the endogenous ho-1 gene is also inhibited by the Nrf2 mutant. Mutations of E1 that inhibit cadmium inducibility also suppress the trans-activation and DNA binding activities of Nrf2, and SB203580, but not PD098059, attenuates Nrf2-mediated trans-activation of pE1-luc. Taken together, these results indicate that cadmium induces ho-1 gene expression via sequential activation of the p38 kinase pathway and Nrf2.

Mechanism of hemoglobin-induced protection against endotoxemia in rats: a ferritin-independent pathway.

Hemoglobin (Hb) induces heme oxygenase-1 (HO-1), which catalyzes the breakdown of heme to bilirubin, and ferritin. Rats pretreated with Hb have been shown to survive lethal doses of lipopolysaccharide (LPS; see L. Otterbein, S. L. Sylvester, and A. M. Choi. Am. J. Respir. Cell Mol. Biol. 13: 595-601, 1995). The physiological basis of this increased survival and the mechanism(s) involved in the protection against LPS by Hb are unknown. Here we investigated 1) the effects of Hb on the hemodynamic and biochemical parameters of LPS-induced tissue injury and 2) the mechanism(s) by which Hb conferred protection against shock and tissue injury. Hb-treated rats maintained normal mean arterial blood pressure, whereas control rats experienced cardiovascular collapse after a lethal dose of LPS. Hepatic and renal functions, peripheral white blood cells, serum lactate dehydrogenase, and phosphate also remained normal after LPS in Hb-treated rats. Hb also attenuated LPS-induced neutrophil alveolitis and tumor necrosis factor-alpha levels. Pretreatment with both desferoxamine, which, like ferritin, can bind iron, and with exogenous apoferritin failed to protect against LPS. In contrast, treatment with Hb plus desferoxamine, which induced HO-1 but not ferritin, did protect against LPS. Treatment with iron-dextran, which induced ferritin but not HO-1, did not protect against LPS. We conclude that Hb pretreatment reduces the inflammatory and physiological consequences of LPS and that the Hb-induced protection against LPS is dependent on HO-1 and not ferritin induction.

Oxidant stress responses in influenza virus pneumonia: gene expression and transcription factor activation.

The pathogenesis of influenza virus infections of the lungs is in part mediated by oxidative stress. Such infections might therefore be expected to induce expression of stress-response genes and genes encoding antioxidant enzymes and to activate transcriptional regulatory proteins. Mice (C57B1/6 and C3H/HeJ) were infected intranasally with influenza virus A/PR/8/34 (H1N1). Expression of the genes encoding the antioxidant enzymes manganese superoxide dismutase (Mn- SOD), indoleamine-2, 3-dioxygenase (IDO), heme oxygenase-1, and glutathione peroxidase were increased in the lungs of virus-infected animals. Cu/ZnSOD and catalase mRNA were not induced by viral infection. Activation of the transcriptional regulatory proteins AP-1, C/EBP, and NF-kappa B (which are known to be affected by oxidant stress) was demonstrated by electrophoretic mobility shift assay after viral infection. In the case of MnSOD, despite increased gene expression enzyme activity was not increased. In contrast, for heme oxygenase-1 both mRNA and activity were increased. C3H/ HeJ and C57B1/6 mice, which are known to have different responses to other types of oxidant stress, also differed in their responses to viral infection. Induction of heme oxygenase-1 expression was greater in C57B1/6 mice than in C3H/ HeJ mice, although inhibiting this enzyme did not alter virus-induced mortality. In contrast, IDO was more strongly induced in C3H/HeJ mice. Activation of NF-kappa B was much more marked in C57B1/6 mice than in C3H/HeJ mice. Although virus replication and inflammatory responses were equivalent in the two strains, lung injury (as measured by wet-to-dry wt ratios) and mortality were greater in C3H/HeJ mice than in C57B1/6 mice, a difference that may be related to differing oxidant stress responses. Thus influenza pneumonia causes an oxidant stress response in the lungs, the nature of which is determined in part by the genetic background of the host.

Prehospital cardiac care: illusion of consensus.

To judge standard practice for managing arrhythmias, what an EMT should be able to do in the field, drugs of choice, the success of EMT training, and the quality of EMT performance, clinical algorithms were developed. Branching logic, forcing yes/no decisions and delineating actions for all contingencies helped formalize and systematize EMT management of urgent and emergency cases. The algorithm set was sent to 19 consultants for review of content, sequence, drug dosage, and drug usage. The results indicated lack of consensus on appropriate prehospital cardiac care, but the approval of the algorithm approach.