Alpha-thiolproteinase inhibitor, alpha 1-antitrypsin and serum proteins in suction blister fluid; effect of local glucocorticosteroid treatment

Familial high serum PICP: high even in skin interstitial fluid, suppressible by topical corticosteroid treatment

Circulating C-terminal propeptide of type I procollagen (PICP), mostly originating from bone, is mainly cleared by mannose receptors (MRs) in liver endothelial cells (LECs). We hypothesized that skin macrophage MRs could also play a role in local (in situ) clearance of PICP originating from skin type I procollagen synthesis. We tested this hypothesis in a male subject with a genetic systemic clearance defect, apparently due to an abnormality in MR function in LECs (or in PICP structure). Since skin macrophages may express the same MRs as LECs do, the genetic defect could affect them as well; hence, if elevated PICP concentrations even in skin interstitial fluid (IF) were found in our subject, it would suggest a role for local MR-mediated PICP clearance in skin. Since glucocorticoids (GCs) upregulate MRs in vitro, we measured the effect of topical GC on suction blister fluid (SBF)-PICP of the test person as compared with normal subjects. SBF-PICP was elevated in the case, which was consistent with the hypothesis. Furthermore, the GC-induced decrease was accentuated. The results suggest that skin macrophage MRs can have a role in skin PICP clearance in situ.

Evidence for angiotensin-converting enzyme- and chymase-mediated angiotensin II formation in the interstitial fluid space of the dog heart in vivo

BACKGROUND

We have previously demonstrated that angiotensin II (Ang II) levels in the interstitial fluid (ISF) space of the heart are higher than in the blood plasma and do not change after systemic infusion of Ang I. In this study, we assess the enzymatic mechanisms (chymase versus ACE) by which Ang II is generated in the ISF space of the dog heart in vivo.

METHODS AND RESULTS

Cardiac microdialysis probes were implanted in the left ventricular (LV) myocardium (3 to 4 probes per dog) of 12 anesthetized open-chest normal dogs. ISF Ang I and II levels were measured at baseline and during ISF infusion of Ang I (15 micromol/L, n=12), Ang I+the ACE inhibitor captopril (cap) (2.5 mmol/L, n=4), Ang I+the chymase inhibitor chymostatin (chy) (1 mmol/L, n=4), and Ang I+cap+chy (n=4). ISF infusion of Ang I increased ISF Ang II levels 100-fold (P<0.01), whereas aortic and coronary sinus plasma Ang I and II levels were unaffected and were 100-fold lower than ISF levels. Compared with ISF infusion of Ang I alone, Ang I+cap (n=4) produced a greater reduction in ISF Ang II levels than did Ang I+chy (n=4) (71% versus 43%, P<0.01), whereas Ang I+cap+chy produced a 100% decrease in ISF Ang II levels.

CONCLUSIONS

This study demonstrates for the first time a very high capacity for conversion of Ang I to Ang II mediated by both ACE and chymase in the ISF space of the dog heart in vivo.

Regulation of local angiotensin II formation in the human heart in the presence of interstitial fluid. Inhibition of chymase by protease inhibitors of interstitial fluid and of angiotensin-converting enzyme by Ang-(1-9) formed by heart carboxypeptidase A-like activity

BACKGROUND

Data from in vitro studies suggest that both chymase and ACE contribute to the local generation of angiotensin (Ang) II in the heart. The enzyme kinetics under in vivo conditions are unclear. We thus studied the generation of Ang II by cardiac tissue in the presence of interstitial fluid (IF) that contains a variety of naturally occurring protease inhibitors.

METHODS AND RESULTS

Ang I was incubated with heart homogenate in the presence of IF. IF obtained from human skin contained substantial amounts of protease inhibitors and ACE activity, the concentration of alpha 1-antitrypsin being 35% and the activity of ACE 24% of the corresponding serum values. When heart homogenate was incubated with Ang I, three enzymes were responsible for its metabolism: heart chymase and heart ACE converted Ang I to Ang II, and heart carboxypeptidase A (CPA)-like activity degraded Ang I to Ang-(1-9). Incubation of heart homogenate in the presence of IF led to practically full inhibition of heart chymase-mediated Ang II formation by the natural protease inhibitors present in IF. In contrast, heart CPA-like activity was not blocked, as reflected by the continued generation of Ang-(1-9). In addition, both heart ACE- and IF ACE-mediated Ang II formation were strongly inhibited. This inhibition was shown to be due to the Ang-(1-9) formed.

CONCLUSIONS

The present experimental study defines two novel inhibitory mechanisms of Ang II formation in the human heart interstitium. Heart chymase-mediated Ang II formation is strongly inhibited by the natural protease inhibitors present in the IF. Similarly, both heart ACE- and IF ACE-mediated Ang II formation appear to be inhibited by the endogenous inhibitor Ang-(1-9) formed by heart CPA-like activity. These inhibitory mechanisms provide additional information about how the Ang II concentration in the heart interstitium may be controlled.

A new method to measure type I and III collagen synthesis in human skin in vivo: demonstration of decreased collagen synthesis after topical glucocorticoid treatment

Collagen is synthesized as procollagen and large extra domains known as propeptides are cleaved off enzymatically. In the present study we have measured the carboxyterminal propeptide of type I collagen (PICP) and the aminoterminal propeptide of type III collagen (PIIINP) in blister fluids of human skin. High concentrations of PICP were found in the spontaneous blisters of patients with bullous pemphigoid, erysipelas, or erythema multiforme. Detectable amounts were also found in suction blisters induced on healthy skin. Because the concentrations in suction blisters were several times higher than in corresponding serum, most of PICP and PIIINP was derived from the underlying dermis. This method was used for assessing type I and type III collagen synthesis after topical glucocorticoid treatment. Clobetasol-17-propionate (CP) decreased the concentrations of PICP by 75% after 1 d of treatment, the maximum inhibition (92%) being found after 2 d treatment. PIIINP was also affected. Hydrocortisone and hydrocortisone-17-butyrate also decreased the concentrations of PICP and PIIINP, but less markedly than CP. Partial recovery was seen 3 d after stopping the treatment. Thus measurement of collagen type specific propeptides in suction blisters can be used as an estimate of collagen synthesis in vivo, avoiding both local anesthesia and skin biopsing. With radioimmunoassays for PICP and PIIINP a large number of samples can also be processed simultaneously.