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VA San Diego Healthcare System San Diego, CA
Correspondence to: Randolph H. Hastings, MD, PhD, Department of Veterans Affairs, VA San Diego Healthcare System, 3350 La Jolla Village Dr, San Diego, CA 92161
To the Editor:
In a recent study (March 2002), Stern et al1 reported that levels of parathyroid hormone-related protein (PTHrP) in BAL fluid negatively correlated with the severity of lung injury in patients with acute lung injury. PTHrP levels were inversely correlated to lung injury score, severity of infiltrates on chest radiographs, and BAL fluid albumin concentration. In addition, PTHrP levels were significantly lower in patients with PaO2/fraction of inspired oxygen (FIO2) ratios < 150 mm Hg compared to patients with PaO2/FIO2 ratios between 150 mm Hg and 300 mm Hg. In other words, patients with lower BAL fluid PTHrP levels had the worst signs of lung injury. The authors suggested that PTHrP might have a role in the alveolar repair process after lung injury. PTHrP has various growth-related effects and is produced by alveolar type II epithelial cells.
We viewed these results with great interest because we are also studying the role of PTHrP in lung injury. Two recent publications not cited in the article by Stern et al1 support their hypothesis that levels of PTHrP in lung epithelial lining fluid correlate negatively with the development of lung injury. Speziale and coworkers2 measured PTHrP levels in tracheal aspirates from newborn infants. PTHrP levels were significantly lower in aspirates from infants born at < 35 weeks’ gestation and with birthweights < 2 kg. In addition, PTHrP levels were significantly lower in male preterm infants compared to female and in preterm infants with respiratory distress syndrome. Furthermore, preterm infants exposed to steroids before birth had higher levels of PTHrP. Thus, PTHrP correlated with several indexes of lung maturation. In another study, Hastings and colleagues3 assayed PTHrP levels in BAL fluid from patients undergoing pulmonary thromboendarterectomy. Patients with lung injury developing following the thromboendarterectomy, based on PaO2/FIO2 < 300 mm Hg and the presence of bilateral lung infiltrates, had significantly lower BAL fluid levels of PTHrP than patients without lung injury. The difference was apparent preoperatively, before the insult occurred, suggesting that PTHrP might be a useful prognostic factor to predict lung injury in this model. Since alveolar type II cells are the major source for PTHrP in the adult and fetal lung, these two studies and the study by Stein et al1 suggest that PTHrP in BAL fluid may be a measure of type II cell function.
References
Inserm Unit 408, Faculté Bichat Paris, France Groupe Hospitalier Bichat-Claude Bernard Paris, France
Correspondence to: Bruno Crestani, MD, PhD, Service de Pneumologie, Groupe Hospitalier, Bichat-Claude Bernard, 46 rue Henri-Huchard, 75877 Paris Cedex 18, France
To the Editor:
The research team of Drs. Hasting and Deftos performed very important work in the field of parathyroid hormone-related protein (PTHrP) and lung biology. We appreciate their comments concerning our article. Speziale and colleagues1 measured PTHrP in tracheal aspirates in preterm infants, and in BAL fluid after pulmonary thromboendarterectomy.2 We commented upon the first paper in our article (see "Discussion" section); however, the citation was omitted. We apologize for this mistake. The second paper was published after our article had been accepted for publication.
We agree with Drs. Hastings and Deftos that our results,3 together with their data, support the hypothesis that PTHrP in BAL fluid may be a measure of type II cell function.
References
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