Hormone sensitive lipase mRNA in both monocyte and macrophage forms of thehuman THP-1 cell line

The identity of the neutral cholesteryl ester hydrolase (CEH) in human mono cyte/macrophages is uncertain. Prior studies indicate that hormone sensitiv e lipase (HSL) is a major CEH in mouse macrophages. and that HSL mRNA is pr esent in human THP-1 monocytes. In the present study, HSL mRNA expression w as examined in THP-1 cells as a function of differentiation status and chol esterol enrichment. By RT-PCR with primer pairs that span exon boundaries, HSL mRNA was demonstrated in THP-1 monocytes and phorbol-ester differentiat ed THP-1 macrophages. cDNA identities were confirmed by sequencing. By Nort hern blotting, with HSL cDNA as probe. THP-1 monocytes were found to contai n HSL mRNA of approximately 3 and 3.9 kb. In THP-1 macrophages. the 3 kb mR NA was greatly diminished, while the level of the 3.9 kb mRNA was maintaine d. mRNA of approximately 3 and 3.9 kb are those expected of the 86-kDa (adi pocyte) and 117-kDa (testicular) HSL isoforms, respectively. The presence o f the testicular isoform mRNA was confirmed in THP-1 cells by amplification and sequencing of an isoform-specific cDNA. Additionally, Northern-blot co mparisons showed that the 3 and 3.9 kb mRNA in THP-1 comigrated with the HS L mRNA in 3T3-L1 adipocytes and rat testis, respectively. The level of the 3.9 kb mRNA did not vary greatly with cholesterol enrichment. Thus, the HSL gene is transcribed in THP-1 cells both before and after differentiation i nto macrophages; after differentiation, the predominant mRNA is that for th e 117-kDa isoform. This isoform is a CEH, and may mediate some CE turnover in THP-1 cells. (C) 2000 Elsevier Science Inc. All rights reserved.