Crocidolite induces prostaglandin I(2) release mediated by vitronectin receptor and cyclooxygenase-2 in lung cells

Our plain-English summary of Crocidolite induces prostaglandin I(2) release mediated by vitronectin receptor and cyclooxygenase-2 in lung cells, by F.J. Leyva, K. Roberts (Lung, 2010).

The study

• Authors: F.J. Leyva, K. Roberts
• Journal: Lung
• Published: 2010;188(2):133-41
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Interstitial lung disease (ILD) produces disruption of alveolar walls with loss of functionality and scar tissue accumulation. Asbestosis is the ILD produced by the inhalation of asbestos fibers. This study attempts to elucidate the role of lung epithelial cells in the generation of asbestos-induced ILD. When exposed to crocidolite LA-4 cells had a decrease in viability and an increase in the release of lactate dehydrogenase (LDH) and 6-keto PGF(1alpha), a PGI(2) metabolite. PGI(2) release was mediated by cyclooxygenase-2 (COX-2) and vitronectin receptor (VNR). When LA-4 cells were treated with VNR inhibitors, either RGD (Arg-Gly-Asp) peptide or VNR blocking antibody, a statistically significant decrease in PGI(2) metabolite production was observed, but crocidolite-induced cytotoxicity was not prevented. These findings propose that crocidolite is coated by an RGD protein and binds VNR-inducing COX-2 expression and PGI(2) release. Moreover, when LA-4 cells were exposed to crocidolite in the presence of reduced serum culture media, PGI(2) production was prevented, and when bronchoalveolar lavage fluid (BALF) was added, PGI(2) production was rescued. Cytotoxicity did not occur, either in reduced serum culture media or when BALF was added. In conclusion, crocidolite requires the presence of an RGD protein coating the fibers to induce inflammation (PGI(2) production) and crocidolite alone cannot induce cytotoxicity in lung cells.

In plain English

This was a laboratory (in vitro) study of LA-4 cells, an immortalised murine lung epithelial cell line described as alveolar type II cell-like, exposed to crocidolite asbestos for 24 hours. Crocidolite (5, 10 and 20 micrograms per cm2) produced a dose-dependent fall in cell viability and, at 20 micrograms per cm2, increased lactate dehydrogenase (LDH) release. At 10 micrograms per cm2 there was a statistically significant rise in 6-keto PGF1alpha, a metabolite of prostaglandin I2 (PGI2). Indomethacin (COX-1/COX-2 inhibitor) and indomethacin heptyl ester (COX-2 inhibitor) reduced this PGI2 metabolite, and COX-2 mRNA rose more than fivefold two hours after exposure, returning to basal levels by four hours. The cells expressed the alpha-v integrin subunit; RGDS peptide reduced PGI2 production by 20% and a vitronectin receptor (VNR) blocking antibody by more than 20%, but neither prevented cytotoxicity, nor did COX inhibitors. In reduced-serum medium no PGI2 was released; adding mouse bronchoalveolar lavage fluid (BALF) restored PGI2 release but not cytotoxicity.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: In vitro cell culture (cell line) experiment, with bronchoalveolar lavage fluid obtained from mice
• Who was studied: LA-4 cells (lung adenoma clone 4) derived from A/He strain mouse, alveolar type II cell-like; bronchoalveolar lavage fluid obtained from five female BALB/c mice aged 6-8 weeks
• Exposure: Crocidolite asbestos (amphibole) applied to cultured cells at 5, 10, 15 and 20 micrograms per cm2 for 24 hours, with or without COX inhibitors, RGDS peptide, VNR blocking antibody, reduced serum medium or 25% BALF
• Main results:
  • LA-4 cells showed a dose-dependent decrease in viability with crocidolite at 5, 10 and 20 micrograms per cm2, and increased LDH release at 20 micrograms per cm2
  • Crocidolite at 10 micrograms per cm2 produced a statistically significant increase in the PGI2 metabolite 6-keto PGF1alpha in exposed LA-4 cells
  • Indomethacin and the COX-2 inhibitor indomethacin heptyl ester reduced PGI2 metabolite production after crocidolite exposure
  • COX-2 mRNA in LA-4 cells rose more than fivefold 2 hours after crocidolite exposure and returned to basal levels at 4 hours
  • COX inhibitors did not protect LA-4 cells from crocidolite-induced cytotoxicity
  • In cells exposed to crocidolite at 20 micrograms per cm2, RGDS peptide or VNR blocking antibody significantly reduced PGI2 metabolite production (about 20% and more than 20% respectively)
  • Neither RGDS peptide nor VNR blocking antibody prevented crocidolite-induced cytotoxicity of LA-4 cells
  • In reduced serum medium LA-4 cells released no PGI2 on crocidolite exposure; adding 25% BALF restored PGI2 release, while reduced serum protected against cytotoxicity and BALF did not increase it
  • Flow cytometry showed LA-4 cells constitutively express the alpha-v integrin subunit common to all vitronectin receptors
• The authors' conclusion: The authors concluded that crocidolite alone could not induce either PGI2 production (inflammation) or cytotoxicity: PGI2 release required an RGD protein coating the fibers acting through the vitronectin receptor and COX-2, while cytotoxicity required one or more factors present in fetal bovine serum and was independent of VNR and COX
• Limitations the authors state:
  • The authors noted that modelling responses with a murine alveolar type II tumour cell line has limitations arising from differences in growth rate and contact inhibition, and that findings need to be checked in primary lung epithelial cells or animal studies
  • The authors stated they did not test for the presence of vitronectin in the BALF or FBS
  • The authors noted the 20% reduction with RGD peptides suggests other, non-RGD-dependent mechanisms also contribute to PGI2 production

Topics

The National Library of Medicine indexes this study under subjects our site covers: Crocidolite.

Medical terms in this study, explained in our Lexicon: Crocidolite, Vitronectin, Interstitial Lung Disease, Lactate Dehydrogenase (LDH), Bronchoalveolar Lavage (BAL), Inflammation.

Related studies

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• Cyclooxygenase-2, epidermal growth factor receptor, and aromatase signaling in inflammation and mesothelioma — B. Nuvoli, R. Galati (2013)
• Phagocytosis of crocidolite asbestos induces oxidative stress, DNA damage, and apoptosis in mesothelial cells — W. Liu, J.D. Ernst, et al. (2000)
• Crocidolite asbestos inhibits pentose phosphate oxidative pathway and glucose 6-phosphate dehydrogenase activity in human lung epithelial cells — C. Riganti, E. Aldieri, et al. (2002)
• Vitronectin enhances internalization of crocidolite asbestos by rabbit pleural mesothelial cells via the integrin alpha v beta 5 — A.M. Boylan, D.A. Sanan, et al. (1995)
• Apoptosis induced by crocidolite asbestos in human lung epithelial cells involves inactivation of Akt and MAPK pathways — A. Baldys, P. Pande, et al. (2007)

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