5-, 12- and 15-Hydroxyeicosatetraenoic acids induce cellular hypertrophy in the human ventricular cardiomyocyte, RL-14 cell line, through MAPK- and NF-κB-dependent mechanism.

Recent studies have established the role of mid-chain hydroxyeicosatetraenoic acids (HETEs) in the development of cardiovascular disease. Mid-chain HETEs have been reported to have vasoconstrictive and pro-inflammatory effects. However, whether mid-chain HETEs can induce cardiac hypertrophy remains unclear. Therefore, the overall objective of the present study was to elucidate the potential hypertrophic effect of mid-chain HETEs in the human ventricular cardiomyocytes, RL-14 cells, and to explore the mechanisms involved. For this purpose, RL-14 cells were treated with increasing concentrations of mid-chain HETEs (2.5, 5, 10 and 20 µM). Thereafter, the cardiac hypertrophy markers and cell size were determined using real-time polymerase chain reaction and phase contrast imaging, respectively. Phosphorylated mitogen-activated protein kinase (MAPK) level and nuclear factor kappa B (NF-κB) binding activity were determined. Our results showed that mid-chain HETEs induced cellular hypertrophy in RL-14 cells as evidenced by the induction of cardiac hypertrophy markers, α- and ß-myocin heavy chain and atrial and brain natriuretic peptide as well as the increase in cell size. Mechanistically, all mid-chain HETEs were able to induce the binding activity of NF-κB to its responsive element in a HETE-dependent manner, and they significantly induced the phosphorylation of ERK 1/2. The induction of cellular hypertrophy was associated with proportional increase in the formation of dihydroxyeicosatrienoic acids parallel to the increase of soluble epoxide hydrolase enzyme activity. In conclusion, our study provides the first evidence that mid-chain HETEs induce cellular hypertrophy in RL-14 cells through MAPK- and NF-κB-dependent mechanism.

Modulation of gentamicin-induced acute kidney injury by myo-inositol oxygenase via the ROS/ALOX-12/12-HETE/GPR31 signaling pathway.

In this investigation, a potentially novel signaling pathway in gentamicin-induced acute kidney injury-worsened by overexpression of proximal tubular enzyme, myo-inositol oxygenase (MIOX)-was elucidated. WT, MIOX-transgenic (MIOX-Tg), and MIOX-KO mice were used. Gentamicin was administered to induce tubular injury. MIOX-Tg mice had severe tubular lesions associated with increased serum creatinine and proteinuria. Lesions were relatively mild, with no rise in serum creatinine and no albuminuria in MIOX-KO mice. Transfection of HK-2 cells with MIOX-pcDNA led to increased gentamicin-induced reactive oxygen species (ROS). Marked increase of ROS-mediated lipid hydroperoxidation was noted in MIOX-Tg mice, as assessed by 4-HNE staining. This was associated with increased expression of arachidonate 12-lipoxygenase (ALOX-12) and generation of 12-hydroxyeicosatetraenoic acid (12-HETE). In addition, notable monocyte/macrophage influx, upregulation of NF-κB and inflammatory cytokines, and apoptosis was observed in MIOX-Tg mice. Treatment of cells with ALOX-12 siRNA abolished gentamicin-mediated induction of cytokines and 12-HETE generation. HETE-12 treatment promoted this effect, along with upregulation of various signaling kinases and activation of GPCR31. Similarly, treatment of cells or mice with the ALOX-12 inhibitor ML355 attenuated inflammatory response, kinase signaling cascade, and albuminuria. Collectively, these studies highlight a potentially novel mechanism (i.e., the ROS/ALOX-12/12-HETE/GPR31 signaling axis) relevant to gentamicin-induced nephrotoxicity modulated by MIOX.