The role of protein kinase C and calcium in induction of human polymorphonuclear leukocyte IL-1 beta gene expression by GM-CSF

Low-Chlorinated Non-Dioxin-like Polychlorinated Biphenyls Present in Blood and Breast Milk Induce Higher Levels of Reactive Oxygen Species in Neutrophil Granulocytes than High-Chlorinated Congeners

Despite their ban several decades ago, polychlorinated biphenyls (PCBs) still pose a health threat to human beings due to their persistent and accumulative nature and continued presence in the environment. Non-dioxin-like (NDL)-PCBs have earlier been found to have effects on the immune system, including human neutrophil granulocytes. The aim of this study was to investigate the differences between ortho-chlorinated NDL-PCBs with a low or high degree of chlorination in their capability to induce the production of reactive oxygen species (ROS) in human neutrophil granulocytes in vitro. We used some of the congeners occurring at the highest levels in blood, breast milk and food: PCB 52 representing the low-chlorinated congeners and PCB 180 the high-chlorinated congeners. In addition, the extensively studied PCB 153 was included as a reference compound. ROS production was assessed with the luminol-amplified chemiluminescence and DCF fluorescence assays. The involvement of intracellular signalling mechanisms was investigated using different pharmacological substances. At high concentrations (10-20 μM), PCB 52 induced more ROS than PCB 153 and PCB 180. The role of extracellular signal-regulated kinase (ERK) 1/2 and/or ERK 5 signalling in PCB-induced ROS production was implicated through the reduction in ROS in the presence of the specific inhibitor U0126, whereas reduced ROS production after the use of SB203580 and SP600125 indicated the involvement of the p38 mitogen-activated protein kinase (MAPK) and c-Jun amino-terminal kinase (JNK) pathways, respectively. In addition, the calcineurin inhibitor FK-506, the intracellular calcium chelator BAPTA-AM and the antioxidant vitamin E reduced the levels of ROS. The intracellular signalling mechanisms involved in ROS production in human neutrophil granulocytes appeared to be similar for PCB 52, PCB 153 and PCB 180. Based on the results from the present and previous studies, we conclude that for abundant ortho-chlorinated PCBs found in the blood, low-chlorinated congeners induce higher production of ROS in neutrophil granulocytes than high-chlorinated congeners. This could be relevant during acute exposure scenarios when high concentrations of PCBs are present.

Tumour necrosis factor alpha mediates transient receptor potential vanilloid 1-dependent bilateral thermal hyperalgesia with distinct peripheral roles of interleukin-1beta, protein kinase C and cyclooxygenase-2 signalling

TNFalpha plays a pivotal role in rheumatoid arthritis (RA) but little is known of the mechanisms that link the inflammatory and nociceptive effects of TNFalpha. We have established a murine model of TNFalpha-induced TRPV1-dependent bilateral thermal hyperalgesia that then allowed us to identify distinct peripheral mechanisms involved in mediating TNFalpha-induced ipsilateral and contralateral hyperalgesia. Thermal hyperalgesia and inflammation were assessed in both hindpaws following unilateral intraplantar (i.pl.) TNFalpha. The hyperalgesic mechanisms were analysed through pharmacogenetic approaches involving TRPV1(-/-) mice and TRPV1 antagonists. To study the mediators downstream of TNFalpha, cyclooxygenase (COX) and PKC inhibitors were utilised and cytokine and prostaglandin levels assessed. The role of neutrophils was determined through use of the selectin inhibitor, fucoidan. We show that TNFalpha (10pmol) causes thermal hyperalgesia (1-4h) in the ipsilateral inflamed and contralateral uninjured hindpaws, which is TRPV1-dependent. GF109203X, a PKC inhibitor, suppressed the hyperalgesia indicating that PKC is involved in TRPV1 sensitisation. Ipsilateral COX-2-derived prostaglandins were also crucial to the development of the bilateral hyperalgesia. The prevention of neutrophil accumulation with fucoidan attenuated hyperalgesia at 4 but not at 1h, indicating a role in the maintenance but not in the induction of bilateral hyperalgesia. However, TNFalpha-induced IL-1beta generation in both paws and the presence of local IL-1beta in the contralateral paw were essential for the development of bilateral hyperalgesia. These results identify a series of peripheral events through which TNFalpha triggers and maintains bilateral inflammatory pain. This potentially allows a better understanding of mechanisms involved in TNFalpha-dependent pain pathways in symmetrical diseases such as arthritis.

In vitro--transcriptional response of polymorphonuclear leukocytes following contact with different antigens

Background Human polymorphonuclear neutrophils (PMN) are activated and undergo apoptosis if brought into contact with cuprophane haemodialysis membranes, a phenomenon not observed if more 'biocompatible' polysulfone dialysers are used. It remains yet to be defined if this differential response is due to mechanisms regulated on a transcriptional or protein level. Furthermore, it is not clear if the contact of PMN with membranes ('frustrated' phagocytosis) activates the same response as phagocytosis of bacteria (complete phagocytosis). Materials and methods We performed a genome-wide differential gene expression study using cDNA microarrays to analyse the impact of different dialysis fibres on the transcriptional response of PMN of human healthy volunteers. These results were compared to transcriptional response of PMN during phagocytosis of Escherichia coli. Results We did not detect significant differences in gene expression between PMN stimulated with cuprophane or pulysulfone. Compared to unstimulated PMN the 'frustrated' phagocytosis of either dialysis membrane resulted in increased expression of 50 genes, with a marked up-regulation of FOS - and JUN - transcripts, but with only little activation of immune response genes, and virtually no activation of apoptosis related RNA transcripts. In contrast, phagocytosis of E.coli was associated with a striking up-regulation of 88 genes, most of them involved in pro- and antiapoptotic pathways, immune response and activation of nuclear factor kappa B and inhibitor of NF-kappa B. Conclusions Our results suggest that the response of PMN to artificial surfaces is not controlled on transcriptional level. Complete and 'frustrated' phagocytosis activate markedly distinct transcriptional regulatory pathways in PMN.

Ciprofloxacin transport by chemoattractant-activated polymorphonuclear leukocytes: regulation by priming and protein kinase C

At infection sites, polymorphonuclear leukocyte (PMN) function is enhanced ("primed") by granulocyte-macrophage colony-stimulating factor (GM-CSF) or lipopolysaccharide (LPS) and activated by formyl peptides. In this study, GM-CSF or LPS alone had no significant effects on PMN ciprofloxacin transport. Through a mechanism involving protein kinase C, activation by formyl-Met-Leu-Phe (fMLP) significantly decreased the K(m) of ciprofloxacin transport and enhanced ciprofloxacin accumulation. This effect was dramatically enhanced when PMNs were primed with GM-CSF or LPS prior to activation by fMLP.

Roles of p38 mitogen-activated protein kinase, NF-kappaB, and protein kinase C in proinflammatory cytokine mRNA expression by human peripheral blood leukocytes, monocytes, and neutrophils in response to Anaplasma phagocytophila

Anaplasma phagocytophila, an obligately intracellular bacterium of granulocytes, causes human granulocytic ehrlichiosis. Within 2 h after addition of A. phagocytophila, interleukin-1beta (IL-1beta), tumor necrosis factor alpha (TNF-alpha), and IL-6 mRNAs are induced in human peripheral blood leukocytes (PBLs) or monocytes in vitro. However, neutrophils generate only IL-1beta mRNA. In the present study, signaling pathways for induction of these three cytokines were examined. TNF-alpha and IL-6 mRNA expression by PBLs was inhibited with SB 203580 (a p38 mitogen-activated protein kinase [MAPK] inhibitor), MG-132 (a proteasome inhibitor), and SN-50 (an NF-kappaB inhibitor). Activation of p38 MAPK and NF-kappaB mRNAs in monocytes was detectable within 15 to 30 min after addition of A. phagocytophila. Expression of these two cytokine mRNAs in PBLs and monocytes was also dependent on protein kinase C (PKC), protein kinase A (PKA), and protein tyrosine kinase (PTK). IL-1beta mRNA expression by neutrophils was not dependent on p38 MAPK, and p38 MAPK was not activated in neutrophils incubated with A. phagocytophila. IL-1beta mRNA induction by PBLs, monocytes, and neutrophils was dependent on PKC and PKA. Neutrophil expression of IL-1beta mRNA was dependent on transglutaminase, phospholipase C, and PTK, all of which are also required for internalization of A. phagocytophila. However, monocyte expression of IL-1beta mRNA was less dependent on these enzymes. These results suggest that A. phagocytophila transduces different signals between its host neutrophils and monocytes for proinflammatory cytokine generation.

Role of Ca(2+) on TNF-alpha and IL-6 secretion from RBL-2H3 mast cells

Ca2+ acts as an important second messenger in mast cells. However, the mechanisms involved in the secretion of inflammatory cytokines from activated mast cells are unknown. In this study, we examined the signaling pathway involved in calcium-related cytokine secretion in a mast cell line, RBL-2H3 cells. We report that treatment with 1,2-bis (2-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester (BAPTA-AM), a chelator of intracellular calcium, can inhibit IgE-stimulated TNF-alpha and IL-6 secretion in a concentration-dependent manner with IC50 values of 0.41 and 0.014 microM, respectively. Maximal inhibition of TNFalpha- and IL-6 secretion was 58.5 +/- 3% and 87 +/- 8% in BAPTA-AM, respectively. BAPTA-AM also completely inhibited the IgE-induced TNF-alpha and IL-6 mRNA levels. In activated RBL-2H3 cells, the expression level of NF-kappaB/Rel A protein increased in the nucleus. However, the level of NF-kappaB/Rel A in nucleus was decreased by treatment of BAPTA-AM. In addition, BAPTA-AM completely inhibited the IgE-induced IkappaB kinase beta (IKKbeta) activation and IkappaBalpha phosphorylation. These observations demonstrate that the intracellular Ca2+ may play an important role in IgE-induced TNF-alpha and IL-6 secretion from mast cells via IKKbeta activation.