No abstract

The characterization and regulation of matrix metalloproteinases (MMPs) have been studied to determine their role(s) in periodontal tissue destruction. Progress in elucidating the roles of MMPs in periodontal tissue destruction has led to a new concept involving the chemotherapeutic inhibition on MMPs, a therapeutic strategy which less than a decade ago was considered "a difficult and perhaps impossible task." Tetracyclines/doxycycline (DOXY) and their chemically modified nonantimicrobial derivatives (CMTs) are known to inhibit the matrix metalloproteinases, especially preferring human neutrophil collagenase (MMP-8), and prevent the oxidative activation of procollagenases. We characterized by Western blotting the molecular forms and cellular sources of gingival tissue, dental plaque, gingival crevicular fluid (GCF), and salivary MMPs associated with periodontitis. Also the molecular forms of tissue inhibitors of matrix metalloproteinases (TIMP-1 and TIMP-2) in periodontitis were studied by Western blot. Neutrophil (PMN)-derived MMPs were found to predominate in periodontitis, and phospholipase C present in increased amounts in periodontitis sites was found to be a potential inducer of PMN degranulation. We further studied the effects of DOXY on molecular forms of different latent and active MMPs purified from different cellular sources (PMNs, fibroblasts, keratinocytes) and present in vivo in oral exudates (gingival extracts, GCF, and saliva). DOXY inhibition of activated (oxidatively or proteolytically) MMPs were not associated with MMP fragmentation. Michaelis-Menten plots of initial rates of degradation of soluble type I collagen revealed an apparent Km value of 0.3-0.6 microM for MMP-8, and 75 microM DOXY inhibited MMP-8 in a manner which did not result in changes in apparent Km value but did prevent the initial degradation reaching Vmax providing evidence for noncompetitive inhibition. Treatment of patients with long-term DOXY medication results in decreased MMP-8 activities/levels in gingival tissue, crevicular fluid, and saliva, but not fragmentation of MMP-8 in vivo. These data further support and extend the key role of PMN-MMPs in periodontitis, and the activities of these PMN MMPs can be inhibited directly by therapeutic levels of DOXY.

The anatomical relationship between corticotropin-releasing factor (CRF)- containing cells and arginine vasopressin (AVP)-containing cells in the human hypothalamus was investigated by immunocytochemistry. In the paraventricular nucleus of the hypothalamus (PVH), CRF-like immunoreactivity (CRF-LI) was present exclusively in parvocellular cells, while AVP-like immunoreactivity (AVP-LI) was present in both parvocellular and magnocellular cells. No CRF-immunoreactive neurons were observed in the supraoptic nucleus. All CRF-immunoreactive parvocellular cells in the PVH were also AVP immunoreactive. We confirmed the presence of AVP in the CRF-immunoreactive cells by using two kinds of anti-AVP antisera, one of which recognized the side chain of AVP while the other recognized the ring structure of AVP. Colocalization of CRF-LI and AVP-LI was observed not only in the same perikarya but also in the same nerve fibers of parvocellular cells. The present results raise the possibility that AVP and CRF may be secreted together into the human portal circulation.

Urocortin is a recently identified neuropeptide of the CRF family in the mammalian brain, but its expression in human tissue has been little studied. In this study, we examined urocortin expression in human anterior pituitary gland and pituitary adenomas by RIA, high performance liquid chromatography, immunohistochemistry, messenger ribonucleic acid (mRNA) in situ hybridization, and reverse transcriptase-PCR. Immunoreactive urocortin concentrations in normal pituitary tissue extract were 103.25 +/- 39.05 ng/g wet wt (mean +/- SEM; n = 4), and their levels were all significantly higher than those in other portions of central nervous system of the same subjects. High performance liquid chromatography analysis of human pituitary extract demonstrated a single peak corresponding to that of the expected chromatographic mobility of synthetic human urocortin-(1-40). Urocortin-immunoreactive cells were detected in the anterior pituitary gland. Neither urocortin-immunoreactive nerve fibers nor cells were detected in the posterior lobe. Immunostaining in serial mirror tissue sections revealed that 76.55 +/- 3.06% of urocortin-immunoreactive cells expressed GH immunoreactivity, whereas 22.25 +/- 3.02% and less than 1% of urocortin-immunoreactive cells expressed PRL and ACTH, respectively. mRNA hybridization signals of urocortin were also detected in urocortin-immunopositive pituitary cells. The reverse transcriptase-PCR analysis demonstrated a 145-bp RNA band corresponding to that of the expected length of urocortin in all cases of normal pituitary glands examined (n = 3). We also immunostained urocortin in 52 cases of human anterior pituitary adenomas, including GH-producing adenomas (n = 14), ACTH-producing adenomas (n = 13), PRL-producing adenomas (n = 11), and nonfunctioning hormonally inactive adenomas (n = 14). No urocortin immunoreactivity was detected in these adenoma cells, except for one case of GH-producing adenoma and one case of nonfunctioning adenoma. We also performed mRNA in situ hybridization in 27 adenomas. No hybridization signals were detected in these adenomas, except in two cases. The results described above indicated that urocortin is synthesized in human anterior pituitary cells and may play an important role in biological features of normal pituitary gland, possibly as an autocrine or a paracrine regulator

The distribution of urocortin in the human central nervous system suggests that urocortin may work as a neurotransmitter like other neuropeptides in the human.