Signal transduction triggered by lipid A-like molecules in 70Z/3 pre-B lymphocyte tumor cells

p38 Mitogen-activated protein kinase and extracellular signal-regulated kinases play distinct roles in the activation of dendritic cells by two representative haptens, NiCl2 and 2,4-dinitrochlorobenzene

Previous studies have demonstrated that haptens induce several phenotypic and functional changes of dendritic cells in vivo as well as in vitro. Although recently, the crucial role of p38 mitogen-activated protein kinase has been reported in the activation of dendritic cells by haptens, the signal transduction elements involved in each phenotypic and functional changes that occur in the activation of dendritic cells by haptens remain unknown. Therefore, we examined the role of mitogen-activated protein kinases and nuclear factor-kappaB in the signal transduction of dendritic cells stimulated with two representative haptens, i.e., NiCl2 and 2,4-dinitrochlorobenzene. Human monocyte-derived dendritic cells stimulated with 2,4-dinitrochlorobenzene induced the phosphorylation of p38 and stress-activated protein kinase/c-jun N-terminal kinases, whereas NiCl2 induced that of p44/42 extracellular signal-regulated kinases, p38, and stress-activated protein kinase/c-jun N-terminal kinases. In addition, NiCl2 phosphorylated inhibitor kappaB and activated nuclear factor-kappaB. In contrast, primary irritants, e.g., benzalkonium chloride, or sodium lauryl sulfate, did not activate these signal transduction pathways. By using specific inhibitors for extracellular signal-regulated kinases and p38 pathways, PD98059 and SB203580, respectively, we demonstrated that the augmentation of CD86, HLA-DR, and CD83, and the production of interleukin-8 along with its increased mRNA expression by monocyte-derived dendritic cells stimulated with 2,4-dinitrochlorobenzene, and the augmentation of CD83 and the interleukin-12 p40 production by monocyte-derived dendritic cells stimulated with NiCl2, were suppressed by SB203580, whereas PD98059 suppressed the production of interleukin-1beta and tumor necrosis factor-alpha, together with their increased mRNA expression by monocyte-derived dendritic cells treated with NiCl2. On the other hand, in spite of the activation of nuclear factor-kappaB by monocyte-derived dendritic cells stimulated with NiCl2, nuclear factor-kappaB inhibitor did not significantly affect the phenotypic and functional changes in the activation of monocyte-derived dendritic cells. These data indicate that NiCl2 and 2,4-dinitrochlorobenzene stimulate different signal transduction pathways in monocyte-derived dendritic cells, and subsequently induce different phenotypic and functional changes in them.

Anti-inflammatory effect of cholecystokinin and its signal transduction mechanism in endotoxic shock rat

AIM: To study the anti-inflammatory effects of cholecystokinin-octapeptide (CCK-8) on lipopolysaccharide (LPS)-induced endotoxic shock (ES) and further investigate its signal transduction pathways involving p38 mitogen-activated protein kinase (MAPK) and IκB-α.

METHODS: Eighty-four rats were divided randomly into four groups: LPS (8 mg·kg^-1, iv) induced ES; CCK-8 (40 μg·kg^-1, iv) pretreatment 10 min before LPS (8 mg·kg^-1); CCK-8 (40 μg·kg^-1, iv) or normal saline (control) groups. The inflammatory changes of lung and spleen, phagocytic function of alveolar macrophage, quantification of inflammatory cells in bronchoalveolar lavage (BAL) were investigated in rats by using hematoxylin and eosin (HE) staining, phagocytosis of Candida albicans and differential cell counting. Nitric oxide (NO) production in serum, lung and spleen was measured with the Griess reaction. The mechanism involving p38 MAPK and IκB-α signal pathways was investigated by Western blot.

RESULTS: Inflammatory changes of lung and spleen induced by LPS were alleviated by CCK-8, the increase of NO induced by LPS in serum, lung and spleen was significantly inhibited and the neutrophil infiltration in BAL was significantly reduced by CCK-8. The number of neutrophils was (52 ± 10) × 10⁶ cells•L^-1 in LPS group, while it decreased to (18 ± 4) × 10⁶ cells•L^-1 in CCK-8+LPS (P < 0.01). The phagocytic rate of CCK-8 group increased to (62.49 ± 9.49)%, compared with control group (48.16 ± 14.20)%, P < 0.05. The phagocytosis rate was (85.14 ± 4.64)% in LPS group, which reduced to (59.33 ± 3.14)% in CCK-8+LPS group (P < 0.01). The results of phagocytosis indexes showed similar changes. CCK-8 may play an important role in increasing the expression of p38 MAPK and decreasing the degradation of IκB-α in lung and spleen of ES rats.

CONCLUSION: CCK-8 can result in anti-inflammatory effects, which may be related to activation of p38 MAPK and inhibition on the degradation of IκB-α.

Paclitaxel-induced immune suppression is associated with NF-kappaB activation via conventional PKC isotypes in lipopolysaccharide-stimulated 70Z/3 pre-B lymphocyte tumor cells

Paclitaxel, a potent antitumor agent, has been shown to be lipopolysaccharide (LPS) mimetic in mice, stimulating signaling pathways and gene expression indistinguishably from LPS. In the present study, we showed the intracellular signaling pathway of paclitaxel-induced nuclear factor-kappaB (NF-kappaB) activation and its suppressive effect on LPS-induced signaling in murine 70Z/3 pre-B cells. Stimulation of 70Z/3 cells with LPS for 30 min caused activation of NF-kappaB in the nuclei by detection of DNA-protein binding specific to NF-kappaB. Similarly, paclitaxel also produced a marked and dose-related NF-kappaB activation. However, pretreatment of cells with 10 microM paclitaxel for 18 h resulted in complete inhibition of LPS-mediated NF-kappaB activation. Interestingly, the activity of IkappaB kinase (IKK-beta), which plays an essential role in NF-kappaB activation through IkappaB phosphorylation, was largely enhanced in paclitaxel-treated cells, detected as IkappaBalpha phosphorylation. Because protein kinase C (PKC) is implicated in the activation of NF-kappaB via IKK-beta, the effect of paclitaxel on PKC activation was also measured. It was shown that NF-kappaB nuclear translocation and DNA binding in response to paclitaxel was completely blocked by the conventional PKC inhibitor, Gö 6976. Moreover, immunoblotting analysis with paclitaxel-treated cell extract demonstrated that the conventional PKC isotype PKC-alpha was found to be involved in the regulation of paclitaxel-induced NF-kappaB activation, as determined by electrophoretic mobility shift of PKC. Therefore, these data suggest that paclitaxel may activate IKK-beta via conventional PKC isotypes, resulting in NF-kappaB activation and, finally, desensitization of LPS-inducible signaling pathway in 70Z/3 pre-B cells.