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[ABSTRACT]AIM:ToinvestigatetheeffectofD4F,anapolipoproteinA-Imimeticpeptide,onoxidizedlow-density lipoprotein ( ox-LDL)-induced macrophage apoptosis and activation of caspase-12, a key molecule in endoplasmic reticulum stress ( ERS )-associated apoptotic pathway, and to elucidate the underlying molecular mechanisms. METHODS:RAW264.7 macrophages were pretreated with D4F (12.5, 25 and 50 mg/L), 4-phenylbutyric acid (PBA, 5 mmol/L) or diphenyleneiodonium ( DPI, 5 μmol/L) for 1 h and then treated with ox-LDL (100 mg/L) or tunicamycin ( TM, 4 mg/L) for 24 h.The cell viability and apoptosis were determined by MTT assay and TUNEL detection, respective-ly.The levels of malondialdehyde ( MDA) and reactive oxygen species ( ROS) in the cells and the activities of superoxide dismutase ( SOD) and nicotinamide adenine dinucleotide phosphate ( NADPH) oxidase were determined.The protein level of caspase-12 was examined by Western blot analysis.RESULTS: Similar to the ERS inhibitor PBA, D4F protected RAW264.7 macrophages from ox-LDL or TM ( an ERS inducer)-induced decrease in the viability and increase in apoptotic rate in a dose-dependent manner.Like DPI (an oxidative stress inhibitor), D4F significantly inhibited ox-LDL-induced ox-idative stress, as expressed by the decreased generation of ROS and MDA ( P<0.01) , the increased activity of SOD and the decreased activity of NADPH oxidase (P<0.05).Moreover, similar to PBA and DPI, D4F significantly suppressed ox-LDL-induced activation of caspase-12 in a concentration-dependent manner ( P<0.05) .Furthermore, D4F also inhibi-ted the caspase-12 activation induced by TM (P<0.05).CONCLUSION: D4F inhibits macrophage apoptosis induced by ox-LDL, and the mechanism is at least partially by reducing oxidative stress and inhibiting the activation of caspase-12.
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Objective To construct a lentiviral vector-based short hairpin RNA (shRNA) targeting the gene encoding tryptophan-aspartate containing coat protein ( TACO) and to evaluate its inhibitory effect on the expression of TACO , and to further elucidate its effects on the phagocytosing and intracellular killing of My-cobacterium tuberculosis (M.tb) by macrophages and the possible mechanisms.Methods Three shRNA frag-ments targeting TACO gene and a scrambling control shRNA fragments were designed and cloned into the lentivi -ral vector pSicoR .The recombinant lentiviral vectors were identified by sequencing analysis and then packed in 293T cells.Real-time RT-PCR and Western blot assay were performed to evaluate the gene-silencing efficiency of the recombinant lentiviral vectors among RAW 264.7 cells transfected with the concentrated lentivirus .The most effective lentivirus was screened out to transfect the RAW 264.7 cells for 48 hours, followed by infection those cells with M.tb strains.The entry and intracellular survival of M .tb strains in RAW264.7 cells were de-termined by bacterial culture at indicated time points .The colocalization of M .tb and lysosomes was detected by immunofluorescence staining .The cyto-ID autophagy kit was used to detect the cellular autophagy and the auto-phagy-associated protein LC 3 was determined by Western blot assay .Results The recombinant lentiviral vec-tors were successfully constructed and confirmed by sequencing analysis .Decreased expression of TACO in RAW264 .7 cells was detected after transfecting the cells with the lentiviral vector-based shRNA vectors targeting TACO gene for 48 hours.The most effective lentivirus , LV-pSRT1, decreased the expression of TACO by 85.24%and 69.00%at the mRNA and protein levels, respectively.The bacterial loads in LV-pSRT1 trans-fected RAW264.7 cells were significantly decreased at the time point of 0 h after M.tb infection as compared with those in the control lentivirus treated cells (5.50×104 vs 8.1 ×104, P<0.05).Compared with the RAW264 .7 cells transfected with control lentivirus , the survival rate of intracellular M .tb strains in LV-pSRT1 transfected cells was significantly decreased at the time point of 48 h (134.54% vs 213.58%, P<0.05) and 72 h (148.18%vs 262.96%, P<0.05) considering the bacterial load at the time point of 0 h as the standard. The immunofluorescence staining demonstrated that the colocalization of M .tb strains with lysosomes was signifi-cantly enhanced in LV-pSRT1 transfected cells as compared with that in control lentivirus treated cells (75.67%vs 10.66%, P<0.05).Moreover, significantly enhanced autophagy and relative expression of LC 3Ⅱ protein were observed in RAW264.7 cells with TACO gene knockdown (16.20%vs 8.50%, P<0.05;0.51 vs 0.34, P<0.05).Conclusion The lentiviral vector-based shRNA targeting TACO gene could effectively knockdown the expression of TACO protein , decrease the entry and increase the intracellular killing of M .tb strains in mac-rophages.The enhanced intracellular killing of M .tb strains by macrophages was associated with the increased fusion of M.tb-containing phagosome and lysosome .