X Yang1, Y Rojanasakul, L Wang, J Y Ma, J K Ma. 1. Department of Basic Pharmaceutical Sciences, West Virginia University, School of Pharmacy, Health Sciences Center, Morgantown 26506, USA.
Abstract
PURPOSE: To investigate the cellular proteolytic activities of various lung pneumocytes using luteinizing hormone releasing hormone (LHRH) and [D-Ala6]-LHRH as model peptide substrates. METHODS: HPLC analysis was used to investigate the degradation kinetics of LHRH/[D-Ala6]-LHRH and to identify their degradation products in isolated lung pneumocytes. RESULTS: Pulmonary macrophages exhibited the strongest proteolytic activity against LHRH)/[D-Ala6]-LHRH, followed by type II and type I-like pneumocytes. Three major degradation products of LHRH, namely LHRH 4-10, LHRH 6-10, and LHRH 7-10, were identified in macrophages and type II pneumocytes, whereas in type I-like pneumocytes only the LHRH 7-10 was found. Co-incubation of the cells with known enzyme inhibitors including captopril (an ACE inhibitor), thiorphan (an EP24.11 inhibitor), and EDTA (an EP24.15 inhibitor) inhibited the formation of LHRH 4-10, LHRH 7-10, and LHRH 6-10 respectively. In all cell types, the degradation rate of [D-Ala6]-LHRH was about 3-8 times lower than that of LHRH. This peptide analog was resistant to degradation by EP24.15 and EP24.11, but was susceptible to ACE. CONCLUSIONS: ACE, EP24.11, and EP24.15 are the major enzymes responsible for the degradation of LHRH in macrophages and type II pneumocytes. The magnitude of peptidase activities in these cell types are: EP24.15 > EP24.11 approximately ACE. No EP24.15 or ACE activity was observed in type I-like pneumocytes and only a weak EP24.11 activity was detected.
PURPOSE: To investigate the cellular proteolytic activities of various lung pneumocytes using luteinizing hormone releasing hormone (LHRH) and [D-Ala6]-LHRH as model peptide substrates. METHODS: HPLC analysis was used to investigate the degradation kinetics of LHRH/[D-Ala6]-LHRH and to identify their degradation products in isolated lung pneumocytes. RESULTS: Pulmonary macrophages exhibited the strongest proteolytic activity against LHRH)/[D-Ala6]-LHRH, followed by type II and type I-like pneumocytes. Three major degradation products of LHRH, namely LHRH 4-10, LHRH 6-10, and LHRH 7-10, were identified in macrophages and type II pneumocytes, whereas in type I-like pneumocytes only the LHRH 7-10 was found. Co-incubation of the cells with known enzyme inhibitors including captopril (an ACE inhibitor), thiorphan (an EP24.11 inhibitor), and EDTA (an EP24.15 inhibitor) inhibited the formation of LHRH 4-10, LHRH 7-10, and LHRH 6-10 respectively. In all cell types, the degradation rate of [D-Ala6]-LHRH was about 3-8 times lower than that of LHRH. This peptide analog was resistant to degradation by EP24.15 and EP24.11, but was susceptible to ACE. CONCLUSIONS:ACE, EP24.11, and EP24.15 are the major enzymes responsible for the degradation of LHRH in macrophages and type II pneumocytes. The magnitude of peptidase activities in these cell types are: EP24.15 > EP24.11 approximately ACE. No EP24.15 or ACE activity was observed in type I-like pneumocytes and only a weak EP24.11 activity was detected.
Authors: Denise A Berti; Cain Morano; Lilian C Russo; Leandro M Castro; Fernanda M Cunha; Xin Zhang; Juan Sironi; Clécio F Klitzke; Emer S Ferro; Lloyd D Fricker Journal: J Biol Chem Date: 2009-03-12 Impact factor: 5.157