Toxicology Letters 135 (2002) 185 – 191 Mechanism of silica-induced ROS generation in Rat2 fibroblast cells Kyoung-Ah Kim a,b , Young-Hoon Kim b , Min Seok Seo c , Woon Kyu Lee c , Seung Won Kim a , Hongtae Kim c , Kweon-Haeng Lee b,c , In-Chul Shin d , Joong-Soo Han e , Hyoung Joong Kim f , Young Lim a, * a Department of Occupational and Enironmental Medicine, St. Mary’s Hospital, The Catholic Uniersity of Korea, 62 Youido -dong, Youngdungpo -gu, Seoul 150 -010, South Korea b Research Institute of New Drug Deelopment, College of Medicine, The Catholic Uniersity of Korea, Seoul, South Korea c Department of Pharmacology, College of Medicine, The Catholic Uniersity of Korea, Seoul, South Korea d Department of Pharmacology, College of Medicine, Hanyang Uniersity, Seoul, South Korea e Department of Biochemistry, College of Medicine, Hanyang Uniersity, Seoul, South Korea f Department of Internal Medicine, College of Medicine, Yonsei Uniersity, Seoul, South Korea Received 4 March 2002; received in revised form 27 May 2002; accepted 29 May 2002 Abstract Reactive oxygen species (ROS) play an important role in cell signaling pathway. Previously, we found that silica induced immediate ROS generation and sequential cellular responses such as kinase activation in Rat2 cells as well as an increase of intracellular calcium concentration in A549 cells. However, the detailed mechanism underlying the immediate ROS generation induced by silica in fibroblast cells remains to be elucidated. Therefore, in the present study, we investigated the mechanism of ROS generation by silica within Rat2 fibroblast cells by examining the effects of a diverse group of inhibitors for the enzymes related with signal transduction events. Inhibitors for protein tyrosine kinase (PTK), phospholipase C (PLC), protein kinase C (PKC) and calmodulin (CaM) kinase II effectively suppressed ROS generation in silica-stimulated Rat2 cells, whereas those for protein kinase A and phospholipase A 2 did not. Diphenyleneiodonium chloride (DPI), an inhibitor for NADPH oxidase was also found to be effective in inhibiting silica-induced ROS generation. These results suggest that PTK, PLC, PKC, CaM kinase II, and NADPH oxidase are all involved in signal transduction pathways for ROS generation in silica-stimulated Rat2 cells. © 2002 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Silica; Fibroblast; ROS; PTK; PLC; PKC; CaM kinase II www.elsevier.com/locate/toxlet 1. Introduction The consumption of oxygen to support the metabolism of living cells leads to the natural and continuous production of reactive oxygen species * Corresponding author. Tel.: +82-2-3779-1401; fax: +82- 2-782-6017 E-mail address: nglim@cmc.cuk.ac.kr (Y. Lim). 0378-4274/02/$ - see front matter © 2002 Elsevier Science Ireland Ltd. All rights reserved. PII: S0378-4274(02)00237-0