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Objective The conventional H1 and H2 histamine receptors have >10,000-fold lower avidity for histamine than H4 histamine receptor, which has been implicated in autoimmune diseases. This study was undertaken to compare H4 histamine receptor levels in the salivary glands (SGs) of healthy controls with those in the SGs of patients with primary Sjögren's syndrome (SS). Methods H4 histamine receptor messenger RNA (mRNA) was analyzed using real-time quantitative polymerase chain reaction, and the receptor protein was examined using immunostaining. Effects of the H4 histamine receptor agonist ST-1006 on cytokine synthesis by human SG (HSG) cells were analyzed using xMAP technology and enzyme-linked immunosorbent assay. Results Healthy SGs contained H4 histamine receptor mRNA. The receptor protein was localized to the acinar and ductal epithelial cells. H4 histamine receptor agonist stimulated HSG cells to produce the cytokines interleukin-8 and vascular endothelial growth factor. SS patients had low H4 histamine receptor levels. Conclusion H1 and H2 histamine receptor antagonists are not effective in the treatment of autoimmune diseases. However, such antagonists do not affect the newly discovered H4 histamine receptor. Dendritic cells and lymphocytes are nonprofessional histamine-producing cells, which produce histamine at 100-1,000-fold lower rates than mast cells do. Saliva contains only 0.31-12.4 ng/ml histamine, which is too low to stimulate H1 or H2 histamine receptor, but stimulates H4 histamine receptor half maximally. Our findings show that H4 histamine receptor is strongly expressed in tubuloacinar SG cells, which emphasizes the role of these cells in the pathogenesis of SS. [ABSTRACT FROM AUTHOR]

OBJECTIVE: Sjögren's syndrome (SS) is characterized by atrophy and malfunction of the acinar cells. The aim of this study was to investigate whether type IV collagen alpha-chain composition of acinar cell compartments could be abnormal in diseased glands. METHODS: Messenger RNA (mRNA) from human submandibular gland (HSG) cells, cultured with or without growth factor-depleted Matrigel, was analyzed using quantitative reverse transcription-polymerase chain reaction (RT-PCR). Labial salivary glands were analyzed using quantitative RT-PCR and immunohistochemistry. RESULTS: HSG cells of both the ductal and acinar phenotypes synthesized all alpha-chain mRNA, in particular those of the alpha1 and alpha2 chains. Labial salivary glands (LSGs) contained alpha1/2 chains but also contained mRNA of all the other alpha-chains, although the mRNA copy numbers for the alpha3 and alpha4 chains were low, and the corresponding proteins were absent. Type IV collagen alpha1/2-chains were observed in all tubuloalveolar basement membranes. In healthy glands, alpha5 and alpha6 chains were continuous around ducts but discontinuous around acini. In SS glands, these chains were absent or patchy around the ducts and absent around the acini. CONCLUSION: Ductal and acinar epithelial cells are able to locally produce mRNA for all 6 different alpha-chains. Type IV collagen alpha1/2-chains seem to form the backbone in the tubuloalveolar basement membrane in salivary glands. Type IV collagen alpha3 and alpha4 chain mRNA were found in cultured salivary epithelial cells and LSG explants but were not translated to the corresponding alpha-chains in LSGs. Both alpha5 and alpha6 mRNA were observed in salivary epithelial cells and glands. In healthy glands, immunolabeling always disclosed corresponding alpha-chains around ducts, but their synthesis and/or degradation seemed to be locally regulated around acinar cells. [ABSTRACT FROM AUTHOR]

OBJECTIVE: Normal synovial lining is composed of macrophage-like type A and fibroblast-like type B lining cells. This sheet-like structure lacks a basement membrane, but its intercellular substance contains some basement membrane components, including type IV collagen. We undertook this study to determine the alpha-chain composition of type IV collagen in normal and arthritic synovial lining, using monoclonal alpha-chain antibodies. METHODS: Samples were analyzed using avidin-biotin-peroxidase complex staining for the presence of collagen alpha1/2(IV), alpha3(IV), alpha4(IV), alpha5(IV), alpha6(IV), matrix metalloproteinase 2 (MMP-2), and MMP-9, and the enzyme activity was detected using gelatin zymography. Double immunofluorescence was performed for type IV collagen/MMP-9 and type IV collagen/CD68. Synovial fibroblasts were studied using quantitative reverse transcriptase-polymerase chain reaction. RESULTS: In mildly inflamed synovium from 5 trauma patients, alpha1/2(IV) chains were strongly stained, but alpha5(IV) and alpha6(IV) chains were weakly stained. Coding messenger RNA was shown in cultured synovial fibroblasts. Basement membranes of blood vessels contained all alpha(IV) chains and served as useful positive sample controls. In the synovial lining from 5 patients with rheumatoid arthritis (RA), all alpha-chains were absent/very weakly stained. This was coupled with numerous type A lining cells containing MMP-9 (type IV collagenase), also found in synovial fluid. CONCLUSION: Synovial lining has a unique and very limited alpha-chain composition, different from that of the vascular basement membrane, which contains all alpha-chains. This special composition and lack of nidogen are probably of relevance for the bidirectional translining diffusion. Such tentative alpha-chain-dependent adhesive and transport-regulating properties seem to be deranged in RA, probably in part due to type IV collagenases produced in the lining and/or released by transmigrating or synovial fluid neutrophils. [ABSTRACT FROM AUTHOR]