A H Daher | PubMed Health

PubMed1997

Effects of exogenous nitric oxide on neutrophil oxidative function and viability.

Previous studies have suggested that nitric oxide (NO) can modulate neutrophil function. Exposure to inhaled NO for pulmonary vasodilation could thus potentially affect neutrophil involvement in lung inflammation and infection. We evaluated the effect of exogenous NO gas exposure at clinically relevant concentrations in vitro on the oxidative function of human neutrophils. Isolated neutrophils were exposed for 2 h to either room air (RA), 80% oxygen (O2), or NO at 20 or 5 ppm blended with room air (NO20/RA, NO5/RA) or blended with 80% oxygen (NO20/O2) (NO5/O2). Neutrophils were then evaluated for superoxide anion generation with the cytochrome c reduction assay, for oxygen consumption with the Clark oxygen electrode technique, and for myeloperoxidase (MPO) release by enzyme-linked immunosorbent assay (ELISA). Neutrophil viability was determined by both trypan blue dye exclusion and fluorescence viability/cytotoxicity assay. Neutrophils exposed to NO at 20 ppm demonstrated a significant decrease in superoxide anion generation in both NO20/RA (97 +/- 46 nmol/10(6) neutrophils) and NO20/O2 (102 +/- 54 nmol/10(6) neutrophils) groups as compared with RA (190 +/- 41 nmol/10(6) neutrophils) (mean +/- SEM, P < 0.005 by analysis of variance [ANOVA] and the Student-Newman-Keuls test). No significant difference was seen at 5 ppm NO exposure. Neutrophil oxygen consumption was decreased with NO20/O2 (6.5 +/- 1.2 nmol O2/ml/min/10(7) neutrophils) as compared with RA (13.7 +/- 3.9 nmol O2/ml/min/10(6) neutrophils) or O2 alone (11.6 +/- 3.1 nmol O2/ml/min/10(7) neutrophils) (P < 0.002). MPO levels were significantly decreased with NO20/O2 (2.3 +/- 0.4 microg/ml) as compared with RA (4.0 +/- 0.4 microg/ml, P < 0.005), and also with NO5/O2. Cell viability as reflected by trypan blue dye exclusion was decreased with O2 (70 +/- 2.3%), NO20/RA (61 +/- 4%), and NO20/O2 (58 +/- 2.5%) exposure as compared with RA control (84.4 +/- 0.9%) (P < 0.0001). Decreased neutrophil viability was confirmed by live/dead assay for O2 (80.8 +/- 2.8%), NO20/RA (62.8 +/- 6.1%), and NO20/O2 (31.7 +/- 5.6%) groups as compared with RA control (95.8 +/- 1.4%, P < 0.0001). Adjusting neutrophil superoxide anion generation, oxygen consumption, and MPO values for cell viability abolished differences between exposure groups. We conclude that exogenous NO exposure at clinically relevant concentrations decreases neutrophil oxidative function, primarily as a result of reduced cell viability. Further studies are necessary to determine if these effects serve an in vivo immunoregulatory or immunosuppressive role in neutrophil response to lung injury and infection.

Adult↗

PubMed1995

Infective endocarditis in neonates.

We studied retrospectively the predisposing factors and signs of infective endocarditis (IE) in neonates and infants younger than 3 months of age, and we suggest diagnostic criteria. The charts of 16 infants less than 3 months of age, diagnosed with IE during a 5-year period, were reviewed for possible maternal and infant risk factors and for pathognomonic clinical and laboratory features. No apparent maternal risk factors were noted. Infant risk factors were congenital heart disease (4), patent ductus arteriosus (PDA) (5), and the use of central venous catheters (14). The main clinical findings were cardiac murmurs (12), petechiae (2), skin abscesses (7), arthritis (2), hepatomegaly (9), and splenomegaly (2). Echocardiography revealed a mass or vegetation in nine patients. Of the 27 microorganisms isolated from blood, the most common were staphylococci (15) and Candida sp. (6). Urine cultures were positive in six patients and cerebrospinal fluid cultures were positive in one. Other laboratory findings were not of diagnostic value. We conclude that the main risk factors for neonatal IE are central venous catheters and congenital heart disease, including PDA. The main causative microorganisms are staphylococci and Candida sp. The main investigations of diagnostic value are blood and urine cultures and echocardiography. We propose the diagnostic categories of definite, probable, and possible cases of neonatal IE, based primarily on clinical, blood culture, and echocardiographic data.

Birth Weight↗