Effects of lipopolysaccharides stimulated Kupffer cells on activation of rat hepatic stellate cells

AIM:To study the effects of Kupffer cell-conditioned medium (KCCM) derived from lipopolysaccharide (LPS) treatment on proliferation of rat hepatic stellate cells (HSC).METHODS:HSC and Kupffer cells were isolated from the liver of Wistar rats by in situ perfusion with pronase and collagenase and density gradient centrifugation with Nycodenz and cultured. KCCM was prepared and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colorimetric assay was used to detect HSC proliferation. The content of type Ⅳ collagen and laminin secreted by HSC in the HSC-conditioned medium was determined by radioimmunoassay.TGF-β1 production in the KCCM was detected by enzymelinked immunosorbent assay (ELISA).RESULTS:HSC and Kupffer cells isolated had high purity.One microgram per mililiter LPS-activated KCCM and unstimulated KCCM could significantly promote HSC proliferation [0.132±0.005 and 0.123±0.008 vscontrol group (0.100±0.003), P<0.01], and there was a difference between them (P<0.05). Ten microgram per mililiter LPS-activated KCCM (0.106±0.010) was unable to promote HSC proliferation (P>0.05). Adding anti-TGF-β1 antibodies could suppress the proliferation promoted by unstimulated KCCM and LPS(1μg/ml)-activated KCCM (0.109±0.009 vs 0.123±0.008,0.115±0.008 vs 0.132±0.005, P<0.01). LPS (1μg/ml or 10μg/ml) could not promote HSC proliferation immediately (0.096±0.003 and 0.101±0.004 vs 0.100±0.003, P>0.05). There was a parallel behavior between HSC proliferation and increased ECM level. One microgram per mililiter LPS-activated KCCM contained a larger amount of TGF-β1 than unstimulated KCCM.CONCLUSION:The technique for isolation of HSC and Kupffer cells described here is simple and reliable. KCCM stimulated by LPS may promote HSC proliferation and collagen accumulation, which are associated with hepatic fibrogenesis.

Alpha-picolinic acid,a fungal toxin and mammal apoptosis-inducing agent,elicits hypersensitive-like response and enhances disease resistance in rice

Alpha-picolinic acid (PA),a metabolite of tryptophan and an inducer of apoptosis in the animal cell,has been reported to be a toxin produced by some of plant fungal pathogens and used in screening for disease resistant mutants. Here,we report that PA is an efficient apoptosis agent triggering cell death of hypersensitive-like response in planta. Confirmed by Fluorescence Activated Cell Sorter (FACS),rice suspension cells and leaves exhibited programmed cell death induced by PA. The PA-induced cell death was associated with the accumulation of reactive oxygen species that could be blocked by diphenylene iodonium chloride,indicating that the generation of reactive oxygen species was NADPHoxidase dependent. We also demonstrated the induction of rice defense-related genes and subsequent resistant enhancement by PA against the rice blast fungus Magnaporthe grisea. Hence,it was concluded that the PA-stimulated defense response likely involves the onset of the hypersensitive response in rice,which also provides a simple eliciting tool for studying apoptosis in the plant cell.

Partial Oxidation of Methane to Formaldehyde over Superfine Mo/ZrO_2 Catalysts

Superfine Mo/ZrO_2 catalysts were prepared for partial oxidation of methane to HCHO and characterized by BET, XRD, LRS, H2-TPR and XPS. Mo existed mainly in the form of Zr(MoO4)2, and the catalytic performance and physicochemical properties of the Mo/ZrO2 catalysts were closely related to this species.

Dynamic Structure of Mo-O Species in Ag-Mo-P-O Catalyst for Oxidative Dehydrogenation of Propane

The dynamic structure of Mo-O species in Ag-Mo-P-O catalyst was studied by in situ confocal microprobe laser Raman spectroscopy (LRS) and catalytic test. The results indicate Mo-O species of MoO3 transformed to Mo-O species of AgMoO2PO4 in C3H8/O2/N2 (3/1/4) flow at 773 K. This behavior is closely relative to oxidative dehydrogenation of propane and intrinsic properties of Mo-O species. The Mo-O species of AgMoO2PO4 may be active species for oxidative dehydrogenation of propane.