Interleukin (IL) -17 is a newly discovered T cell-derived cytokine whose role in osteoclast development has not been fully elucidated. Treatment of co-cultures of mouse hemopoietic cells and primary osteoblastic cells with recombinant human IL-17 induced the formation of multinucleated cells, which satisfied major criteria of osteoclasts such as tartrate-resistant acid phosphatase (TRAP) activity, calcitonin receptors, and pit formation on dentine slices. Direct interaction between osteoclast progenitors and osteoblasts was required for osteoclastogenesis induced by IL-17, which was completely inhibited by adding indomethacin or NS 398, a selective inhibitor of cyclooxgenase-2 (COX-2) . Adding IL-17 increased prostaglandin E2 (PGE2) synthesis both in co-cultures of bone marrow cells and osteoblastic cells and in single cultures of osteoblastic cells, but not in single cultures of bone marrow cells. In addition, IL-17 dose-dependently induced expression of osteoclast differentiation factor (ODF) mRNA in osteoblastic cells. ODF is a membrane-associated protein, which transduces an essential signal (s) to osteoclast progenitors for differentiation into osteoclasts. Osteoclastogenesis inhibitory factor (OCIF), a decoy receptor of ODF, completely inhibited IL-17-induced osteoclast differentiation in the co-cultures. Levels of IL-17 in synovial fluids were significantly higher in rheumatoid arthritis (RA) patients than osteoarthritis (OA) patients (p<0.0001) . Anti-IL-17 antibody significantly inhibited OCL formation in the co-cultures with culture media of RA synovial tissues. These findings suggest that IL-17 first acts on osteoblastic cells, which stimulates both COX-2-dependent PGE2 synthesis and ODF gene expression, which in turn induce differentiation of osteoclast progenitors into mature osteoclasts. IL-17 may be involved in osteoclastic bone resorption in RA patients. It has been reported that IL-17 also produce many factors inducing degradation cartilage in RA. Therefore, IL-17 may play a pivotal role in joint destruction in RA.
UV radiation causes inflammation characterized by erythema and swelling, immunosuppression, apoptosis, melanogenesis, photoaging, and photocarcinogenesis, whereas it also exhibits anti-inflammatory or therapeutic effects as seen in the treatment of psoriasis and atopic dermatitis. Nitric oxide (NO), a reactive gaseous molecule with multiple cellular functions, has been speculated to play pathogenic or protective roles in inflammatory dermatoses. Therefore, it is important to elucidate how UVB radiation regulates or modifies NO production and nitric oxide synthase (NOS) expression in skin. To examine this issue, we used murine cultured keratinocyte Pam 212 cells and found that low doses of UVB radiation significantly suppressed NO production and inducible NOS (iNOS) expression in keratinocytes stimulated by IFN-γ or TNF-α. Taking pathogenic roles of excessive NO produced through iNOS induction into consideration, UVB-induced suppression of NO production may explain in part the anti-inflammatory or therapeutic effects of UVB radiation in inflammatory dermatoses. However, in keratinocytes under nonstimulated condition, UVB radiation increased NO production, where brain NOS (bNOS) mRNA and protein expressions were enhanced and iNOS mRNA expression was suppressed. These results suggest that NO thus produced after UVB radiation in non-inflammatory skin may explain in part the subsequent erythema formation, melanogenesis and other UVB-induced skin reactions.
To examine the regulatory mechanisms of proliferation and maturation in neutrophilic lineage cells, we have found the existence of transferrin receptor (Trf-R) positive (Trf-R+) and negative (Trf-R-) cells in DMSO-treated HL-60 cells and successfully sorted into Trf-R+ and Trf-R- cells. Differentiated Trf-R- cells exhibited much more maturation of neutrophilic cells as compared with Trf-R+ cells, and G-CSF accelerated differentiation of Trf-R- cells. On the other hand, Trf-R+ cells had a tendency to proliferate rather than differentiate, and proliferation has enhanced by G-CSF. These resullts indicate that Trf-R expression coincides with the commitment to proliferate or differentiate of HL-60 cells, and G-CSF accelerates these commitments. On the basis from the results of G-CSF-induced signal transduction in Trf-R+ and Trf-R- cells, STAT 3 promoted the differentiation of HL-60 cells into neutrophils, while p 70 S6 kinase promotes proliferation and negatively regulate neutrophilic differentiation. We also examined cross talk of G-CSF and GM-CSF on the differentiation of HL-60 cells into nuetrophils. While G-CSF accelerate the neutrophilic differentiation of DMSO-treated HL-60 cells, GM-CSF markedly inhibited the G-CSF induced enhancement of neutrophilic differentiation. Furthermore, GM-CSF did not alter the G-CSF induced tyrosine phosphorylation of STAT 3, but GM-CSF inhibited the nuclear translocation of tyrosine-phosphorylated STAT 3. Therefore, we concluded that G-CSF-dependent nuclear translocation of STAT 3 coordinates with the promotion of neutrophilic differentiation in DMSO-treated HL-60 cells.
Prostaglandins play various roles in the brain under physiological as well as pathological conditions. This review summarizes our present knowledge about brain localization of two isoforms of cyclooxygenase, enzymes responsible for prostaglandin biosynthesis, and their possible functions. Cyclooxygenase-1 (COX-1) is con-stitutively expressed in microglia throughout the brain. Little is known about COX-1 function there. COX-1 is also abundantly expressed in the primary sensory neurons both at their cell bodies and at the central terminals in the medulla and spinal cord suggesting its involvement in sensory signal transmissions. COX-2 is constitutively expressed in telencephalic neurons in an activity-dependent manner. This neuronal expression of COX-2 was reported to be involved in the regulation of regional cerebral blood flow. On the other hand, some studies have reported that COX-2 might exert adverse actions after brain ischemia and in Alzheimer's disease. Under various infectious as well as inflammatory conditions, COX-2 is expressed in brain endothelial cells. We presented a large body of evidence that elevation of prostaglandin EZ in the brain and occurrence of fever during infection/inflammation are the consequences of this endothelial expression of COX-2. Thus, brain endothelial cells seem to transmit blood borne cytokine signals to brain by producing prostaglandin E2.
Defensins constitute a family of cationic antimicrobial peptides found in various animals, and act as key elements in the innate host defense. Mammalian defensins are deviled into α- and β-defensin subfamilies. In human, β-defensins (hBDs) are expressed in many epithelial tissues including trachea, skin, and intestine. Interestingly, expression of hBD1 is constitutive, while hBD2 expression is strongly induced in response to bacteria infection and proinflammatory cytokines. The promoter region of hBD2 gene contains several consensus binding sites for NFκB (nuclear factor κB), C/EBPβ (CCAAT/enhancer-binding protein β) and IFN-γ, suggesting inflammatory signaling may elicit the induction of hBD2 expression. However, the regulation mechanism of hBD expressions is little known. To clarify the transcriptional regulation of hBD genes, we investigated their promoter activities in response to LPS using CD 14+ macrophage-like RAW 264.7 cells. The hBD1 promoter was not responsible to LPS, although the region from -162 to -70 was essential for its constitutive transcription. In contrast, the transcriptional activity of hBD2 promoter, which contained 3 potent NFκB binding sites at -2270, -576, and -208, was increased in response to LPS. Mutation or deletion of the NFκB site at -576 caused a 90% decrease in LPS response. Furthermore, gel mobility shift assay indicated that LPS increased NFκB binding activity with the -576 site on the hBD2 promoter. These observations suggest that the interaction between NFκB and the -576 site is important for LPS response of hBD2 promoter. Macrophages and epithelial cells express Toll-like receptors (TLRs) which induce activation of NFκB. Taken together, the TLR-NFκB pathway is likely involved in the LPS-induced transcription of hBD2 gene.
Nonselective nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit the production of primary prostanoids by blocking both cyclooxygenase (COX) -1 and COX-2 activities, and in doing so, not only decrease inflammation and pain, but also promote gastrointestinal tract damage and bleeding. The inhibitory activities of zaltoprofen (ZP) on the biosynthesis of prostaglandin E2 (PGE2) at the inflammatory site and stomach were compared with those of some NSAIDs (celecoxib : CL, meloxicam : ML, lornoxicam : LR, mofezolac : MF) using the rat carrageenin-air pouch model. At the dose of ZP and CL that inhibited PGE2biosynthesis at the inflammatory site, these hardly inhibited the PGE2release from stomach. In contrast, ML, MF and LR inhibited the biosynthesis of PGE2on both sites at the same dose. Furthermore these NSAIDs inhibited the carrageenin-induced paw edema, and produced the ulcer in a dose-dependent manner. The safety index, UD50/ED40ratio, of CL, ZP, ML, LR and MF was >103, 11.3, 0.8, 0.8 and 0.1, respectively. These safety indexes correlated well with the tissue selectivity of NSAIDs on PG biosynthesis inhibition. These results suggest that the PG biosynthesis at the inflammatory site and stomach of the same rat is a very useful parameter for evaluating NSAIDs. It seems that these properties of ZP were contributed to the low ulcerogenic activity on clinical uses.