Inflammatory cytokines in BAL fluid and pulmonary hemodynamics in high-altitude pulmonary edema

Enhanced synthesis of albumin and fibrinogen at high altitude

The acute effects of active and passive ascent to high altitude on plasma volume (PV) and rates of synthesis of albumin and fibrinogen have been examined. Measurements were made in two groups of healthy volunteers, initially at low altitude (550 m) and again on the day after ascent to high altitude (4,559 m). One group ascended by helicopter (air group, n = 8), whereas the other group climbed (foot group, n = 9), so that the separate contribution of physical exertion to the response could be delineated. PV was measured by dilution of (125)I-labeled albumin, whereas synthesis rates of albumin and fibrinogen were determined from the incorporation of isotope into protein after injection of [ring-(2)H(5)]phenylalanine. In the air group, there was no change in PV at high altitude, whereas, in the foot group, there was a 10% increase in PV (P < 0.01). Albumin synthesis (mg. kg(-1). day(-1)) increased by 13% in the air group (P = 0.058) and by 32% in the foot group (P < 0.001). Fibrinogen synthesis (mg. kg(-1). day(-1)) increased by 40% in the air group (P = 0.068) and by 100% in the foot group (P < 0.001). Hypoxia and alkalosis at high altitude did not differ between the groups. Plasma interleukin-6 was increased modestly in both groups but C-reactive protein was not changed in either group. It is concluded that increases in PV and plasma protein synthesis at high altitude result mainly from the physical exercise associated with climbing. However, a small stimulation of albumin and fibrinogen synthesis may be attributable to hypobaric hypoxia alone.

Exhaled nitric oxide in high-altitude pulmonary edema: role in the regulation of pulmonary vascular tone and evidence for a role against inflammation

High-altitude pulmonary edema (HAPE) is a life-threatening condition occurring in predisposed subjects at altitudes above 2,500 m. It is not clear whether, in addition to hemodynamic factors and defective alveolar fluid clearance, inflammation plays a pathogenic role in HAPE. We therefore made serial measurements of exhaled pulmonary nitric oxide (NO), a marker of airway inflammation, in 28 HAPE-prone and 24 control subjects during high-altitude exposure (4,559 m). To examine the relationship between pulmonary NO synthesis and pulmonary vascular tone, we also measured systolic pulmonary artery pressure (Ppa). In the 13 subjects who developed HAPE, exhaled NO did not show any tendency to increase during the development of lung edema. Throughout the entire sojourn at high altitude, pulmonary exhaled NO was roughly 30% lower in HAPE-prone than in control subjects, and there existed an inverse relationship between Ppa and exhaled NO (r = -0.51, p < 0.001). These findings suggest that HAPE is not preceded by airway inflammation. Reduced exhaled NO may be related to altered pulmonary NO synthesis and/or transport and clearance, and the data in our study could be consistent with the novel concept that in HAPE-prone subjects, a defect in pulmonary epithelial NO synthesis may contribute to exaggerated hypoxic pulmonary vasoconstriction and in turn to pulmonary edema.

Serial scintigraphic assessment of iodine-123 metaiodobenzylguanidine lung uptake in a patient with high-altitude pulmonary edema

Iodine-123 metaiodobenzylguanidine ((123)I-MIBG) can be considered an indicator of pulmonary endothelial cell function. Serial (123)I-MIBG images of the chest were acquired in a patient with high altitude pulmonary edema (HAPE). The initial evaluation was performed 7 days after admission. The lung to upper mediastinum ratios (LMRs) of (123)I-MIBG uptake were 1.33 (for the right lung) and 1.12 (for the left lung). The second examination of (123)I-MIBG lung uptake, which was performed 2 months later, showed LMRs of 1.39 (right lung) and 1.33 (left lung). We speculated that the decreased lung uptake of (123)I-MIBG at the early recovery stage could reflect an impairment in pulmonary endothelial cell metabolic function in the development of HAPE.

Pressure is proinflammatory in lung venular capillaries

Endothelial responses may contribute importantly to the pathology of high vascular pressure. In lung venular capillaries, we determined endothelial [Ca(2+)](i) by the fura-2 ratioing method and fusion pore formation by quantifying the fluorescence of FM1-43. Pressure elevation increased endothelial [Ca(2+)](i). Concomitantly evoked exocytotic events were evident in a novel spatial-temporal pattern of fusion pore formation. Fusion pores formed predominantly at vascular branch points and colocalized with the expression of P-selectin. Blockade of mechanogated Ca(2+) channels inhibited these responses, identifying entry of external Ca(2+) as the critical triggering mechanism. These endothelial responses point to a proinflammatory effect of high vascular pressure that may be relevant in the pathogenesis of pressure-induced lung disease.

Proliferation of type II pneumocytes and alteration in their apical surface membrane antigenicity in pulmonary sarcoidosis

STUDY OBJECTIVE

To evaluate both the proliferation of type II pneumocytes in the alveolitis associated with pulmonary sarcoidosis and any alteration in their surface membrane antigenicity.

MATERIALS AND METHODS

We investigated 20 transbronchial lung biopsy (TBLB) specimens from 20 patients with pulmonary sarcoidosis, 7 TBLB specimens from 7 sarcoidosis patients without pulmonary involvement, and 19 normal lung specimens, using colloidal iron stain and immunostaining with anti-Thomsen-Friedenreich (TF) antigen and anti-surfactant protein-A monoclonal antibodies.

RESULTS

The density of type II pneumocytes was significantly higher in the pulmonary sarcoidosis specimens ([mean +/- SD] 11.1+/-3.7 per 1 mm alveolar septal length) than in the nonpulmonary sarcoidosis (7.8+/-1.3) or normal lung specimens (7.2+/-0.8). TF antigen was directly expressed on the apical surface of some type II pneumocytes in the pulmonary sarcoidosis specimens, but it was completely masked by sialic acids in the nonpulmonary sarcoidosis specimens and in the normal lung tissues.

CONCLUSIONS

In pulmonary sarcoidosis, type II pneumocytes proliferated and the antigenicity of the surface membrane was altered. It is suggested that these type II pneumocytes may be vulnerable to injury by natural anti-TF antibodies that are cytotoxic when present with complement. This damage may decrease alveolar surfactant and cause focal alveolar collapse proceeding to pulmonary fibrosis in some cases of pulmonary sarcoidosis.