Cholesterol Research Today is a free monthly online journal that collates and summarizes the latest research about Cholesterol, including details on high cholesterol, hdl, ldl, diet, risks. | ||||||||
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Caspase-8, -12, and -3 activation by 7-ketocholesterol in retinal neurosensory cells.Neekhra A, Luthra S, Chwa M, Seigel G, Gramajo AL, Kuppermann BD, Kenney MC Department of Ophthalmology, School of Medicine, University of California, Irvine, California, USA. mkenney@uci.edu PURPOSE: To determine the caspase pathways involved with 7-ketocholesterol (7kCh)-induced apoptosis in rat R28 cells. METHODS: R28 cells were exposed to 7kCh with or without low-density lipoprotein (LDL) and z-VAD-fmk, a pan-caspase inhibitor. Cell viability was measured by a trypan blue dye exclusion assay. Caspase-3, -8, -9, and -12 activities were measured by fluorochrome caspase assays. ARPE-19 cells were used as control for caspase-3 inhibition experiments. RESULTS: R28 cultures showed decreased cell viability on 7kCh exposure compared with controls (P < 0.001), and this was reversed with LDL and LDL + z-VAD-fmk (P < 0.001). The 7kCh-treated R28 cultures had increased caspase-8 activity compared with controls (P < 0.001). This activity was blocked partially with LDL (P < 0.01) or LDL + z-VAD-fmk (P < 0.001) but not with z-VAD-fmk alone. Caspase-12 activity was increased after 7kCh treatment compared with controls (P < 0.01), and this activity was increased further with the addition of LDL. Caspase-3 activity in R28 cultures increased with 7kCh treatment compared with controls (P < 0.001). In R28 cultures, the z-VAD-fmk treatment did not blocked 7kCh-induced caspase-3 activity but did block activity in ARPE-19 cultures (P < 0.001). Caspase-9 was not activated by 7kCh treatment. CONCLUSIONS: In R28 cells, 7kCh-induced apoptosis involves the caspase-3 along with the caspase-8 and caspase-12 pathways. LDL partially blocked 7kCh-induced caspase-8 activity but increased caspase-12 activities, suggesting that caspase-8 and caspase-12 pathways are independent of each other. The z-VAD-fmk inhibitor blocked caspase-3 activities in the homogeneous ARPE-19 cultures but not in the heterogeneous R28 cultures. Published 27 February 2007 in Invest Ophthalmol Vis Sci, 48(3): 1362-7.
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