Publications

Mammalian hepatic cytochromes P450 (P450s) are endoplasmic reticulum (ER)-anchored hemoproteins engaged in the metabolism of numerous xeno- and endobiotics. P450s exhibit widely ranging half-lives, utilizing both autophagic-lysosomal (ALD) and ubiquitin-dependent 26S proteasomal (UPD) degradation pathways. Although suicidally inactivated hepatic CYPs 3A and "native" CYP3A4 in Saccharomyces cerevisiae are degraded via UPD, the turnover of native hepatic CYPs 3A in their physiological milieu has not been elucidated. Herein, we characterize the degradation of native, dexamethasone-inducible CYPs 3A in cultured primary rat hepatocytes, using proteasomal (MG-132 and MG-262) and ALD [NH4Cl and 3-methyladenine (3-MA)] inhibitors to examine their specific degradation route. Pulse-chase with immunoprecipitation analyses revealed a basal 52% 35S-CYP3A loss over 6 h, which was stabilized by both proteasomal inhibitors. By contrast, no corresponding CYP3A stabilization was detected with either ALD inhibitor NH4Cl or 3-MA. Furthermore, MG-262-induced CYP3A stabilization was associated with its polyubiquitylation, thereby verifying that native CYPs 3A were also degraded via UPD. To identify the specific participants in this process, cellular proteins were cross-linked in situ with paraformaldehyde (PFA) in cultured hepatocytes. Immunoblotting analyses of CYP3A immunoprecipitates after PFA-cross-linking revealed the presence of p97, a cytosolic AAA ATPase instrumental in the extraction and delivery of ubiquitylated ER proteins for proteasomal degradation. Such native CYP3A-p97 interactions were greatly magnified after CYP3A suicidal inactivation (which accelerates UPD), and/or proteasomal inhibition, and were confirmed by proteomic and confocal immunofluorescence microscopic analyses. These findings clearly reveal that native CYPs 3A undergo UPD and implicate a role for p97 in this process.

BACKGROUND

Spirometry is recommended for diagnosis and management of obstructive lung disease. While many patients with asthma and COPD are cared for by primary care practices, limited data are available on the use and results associated with spirometry in primary care.

OBJECT

To assess the technical adequacy, accuracy of interpretation, and impact of office spirometry.

DESIGN

A before-and-after quasiexperimental design.

SETTING

Three hundred eighty-two patients from 12 family medicine practices across the United States.

PARTICIPANTS

Patients with asthma and COPD, and staff from the 12 practices.

MEASUREMENTS

Technical adequacy of spirometry results, concordance between family physician and pulmonary expert interpretations of spirometry test results, and changes in asthma and COPD management following spirometry testing.

RESULTS

Of the 368 tests completed over the 6 months, 71% were technically adequate for interpretation. Family physician and pulmonary expert interpretations were concordant in 76% of completed tests. Spirometry was followed by changes in management in 48% of subjects with completed tests, including 107 medication changes (>85% concordant with guideline recommendations) and 102 nonpharmacologic changes. Concordance between family physician and expert interpretations of spirometry results was higher in those patients with asthma compared to those with COPD.

DISCUSSION AND CONCLUSIONS

US family physicians can perform and interpret spirometry for asthma and COPD patients at rates comparable to those published in the literature for international primary care studies, and the spirometry results modify care.