Lars Jelstrup Petersen

Type I collagen synthesis and degradation in peritendinous tissue after exercise determined by microdialysis in humans

1 Physical activity is known to increase type I collagen synthesis measured as the concentration of biomarkers in plasma. By the use of microdialysis catheters with a very high molecular mass cut‐off value (3000 kDa) we aimed to determine local type I collagen synthesis and degradation in the peritendinous region by measuring interstitial concentrations of a collagen propeptide (PICP; 100 kDa) and a collagen degradation product (ICTP; 9 kDa) as well as an inflammatory mediator (PGE2). 2 Seven trained human runners were studied before and after (2 and 72 h) 3 h of running (36 km). Two microdialysis catheters were placed in the peritendinous space ventral to the Achilles’ tendon under ultrasound guidance and perfused with a Ringer‐acetate solution containing 3H‐labelled human type IV collagen and [15‐3H(N)]PGE2 for in vivo recovery determination. Relative recovery was 37–59% (range of the s.e.m. values) for both radioactively labelled substances. 3 PICP concentration decreased in both interstitial peritendinous tissue and arterial blood immediately after exercise, but rose 3‐fold from basal 72 h after exercise in the peritendinous tissue (55 ± 10 μg l−1, mean ± s.e.m. (rest) to 165 ± 40 μg l−1 (72 h), P < 0·05) and by 25% in circulating blood (160 ± 10 μg l−1 (rest) to 200 ± 12 μg l−1 (72 h), P < 0·05). ICTP concentration did not change in blood, but decreased transiently in tendon‐related tissue during early recovery after exercise only. PGE2 concentration increased in blood during running, and returned to baseline in the recovery period, whereas interstitial PGE2 concentration was elevated in the early recovery phase. 4 The findings of the present study indicate that acute exercise induces increased formation of type I collagen in peritendinous tissue as determined with microdialysis and using dialysate fibre with a very high molecular mass cut‐off. This suggests an adaptation to acute physical loading also in non‐bone‐related collagen in humans.

Allergen-induced histamine release in intact human skin in vivo assessed by skin microdialysis technique: Characterization of factors influencing histamine releasability☆☆☆★★★

BACKGROUND The purposes of the study were to characterize allergen-induced histamine release in intact human skin in vivo by using a novel microdialysis technique and to study covariates influencing histamine releasability. METHODS Hollow microdialysis fibers were inserted into the upper dermis in 15 timothy-sensitivity subjects. Up to 12 fibers were inserted in each subject. Each fiber was perfused with Krebs-Ringers solution at a rate of 3.0 microliters/min. Three to four serial dilutions of allergen were applied to the skin by intracutaneous injections or skin prick test above individual fibers. Samples were collected in two 2-minute fractions before skin challenge and in 10 consecutive samples for 20 minutes after skin challenge. Histamine was assayed spectrofluorometrically. RESULTS A significant dose-response relationship for histamine release was demonstrated with intracutaneous tests and skin prick tests. The time to reach peak histamine release after an intracutaneous test was 4 to 8 minutes, compared with 12 to 14 minutes for a skin prick test. Histamine release correlated significantly with wheal size. Intrasubject coefficient of variation on histamine release was about 20%. A substantial intersubject variation in histamine releasability was observed. Seventy to seventy-five percent of the variation could be accounted for by a combination of gender, total and allergen-specific IgE, and an in vitro basophil histamine release test. CONCLUSIONS Using a skin microdialysis technique, we have described in detail histamine release in intact human skin by allergen. The microdialysis method proved to be a reproducible technique for monitoring histamine release in allergic skin reactions and for studying histamine releasability of skin mast cells in vivo.

Anti-cancer properties of low-molecular-weight heparin: Preclinical evidence

Malignant conditions are frequently associated with a hypercoaguable state, with recurrent thrombosis due to the impact of cancer cells and chemotherapy or radiotherapy on the coagulation cascade. Heparin and, its pharmacokinetically improved versions, low-molecular-weight heparins (LMWH) are effective in the prevention and treatment of thromboembolic events in cancer patients. There are several lines of preclinical evidence suggesting potential benefits of LMWH in hypercoagulation and thrombosis as well as in various processes involved in tumour growth and metastasis. Tinzaparin is a LMWH produced by controlled enzymatic depolymerisation of unfractionated heparin. The efficacy of tinzaparin has been documented in several clinical trials across various conditions and in special patient populations. The main objective of this review is to present the existing knowledge on the preclinical anti-cancer properties of tinzaparin and other LMWH. The evidence for tinzaparin, as well as other LMWH, regarding interference with cancer-induced hypercoagulation, cancer cell proliferation, degradation of extra-cellular matrix, angiogenesis, selectin-mediated binding of platelet and cancer cells, chemokine signalling, tumour progression, and metastasis are reviewed. Certain clinical trials suggest improved survival of cancer patients with deep venous thrombosis treated with LMWH versus unfractionated heparin and when added to the promising preclinical anti-cancer properties of LMWH this warrants further investigations in prospective, randomised, controlled clinical trials in cancer patients. The benefits of LMWH in cancer might at least in part, be independent from its anti-coagulant activities, but may still be partially dependent on its anti-coagulant activities.

Histamine is released in the wheal but not the flare following challenge of human skin in vivo: a microdialysis study

Background The mediator mechanisms of the cutaneous wheal and flare response, which underlies allergic skin and urticarial conditions, are controversial. The wheal results primarily from a direct effect of histamine on the local vascular bed, but to what extent does histamine diffuse within the wheal? The flare is neurogenic in origin, being disseminated within the dermis by axon reflexes, but do the neuropeptides released from the nerve endings cause the vasodilatation directly or do they induce the further release of histamine which then transduces the fiare?

Acute effects of nicotine and smoking on blood flow, tissue oxygen, and aerobe metabolism of the skin and subcutis.

BACKGROUND Nicotine released from tobacco smoke causing reduction in blood flow has been suggested as causative for postoperative wound complications in smokers, but the mechanism remains unknown. MATERIALS AND METHODS In eight healthy male smokers and eight ex-smokers, the cutaneous and subcutaneous blood flow (QBF, SqBF) was assessed by Laser Doppler and 133Xe clearance. Tissue oxygen tension (TO(2)) was measured by a LICOX O(2)-electrode. Tissue glucose and lactate (Tgluc, Tlact) were assessed by microdialysis. The parameters were studied after intravenous infusion of 1.0 mg nicotine, smoking of one cigarette, arterial occlusion, and reperfusion. RESULTS Nicotine infusion decreased SqBF from 4.2 +/- 2.0 to 3.1 +/- 1.2 mL/100 g tissue/min (P < 0.01), whereas QBF was 21.7 +/- 8.6 and 22.7 +/- 9.6 Arbitrary Units (AU), respectively (P = 0.21). TO(2) increased from 49.3 +/- 12.0 to 53.9 +/- 12.0 mm Hg (P = 0.01). Tgluc and Tlact remained unaffected. Smoking decreased SqBF from 4.2 +/- 2.0 to 2.7 +/- 1.2 mL/100 g tissue/min (P < 0.01). QBF decreased from 23.4 +/- 9.2 to 20.3 +/- 7.4 AU (P < 0.01), and TO(2) decreased from 53.9 +/- 12.0 to 48.4 +/- 11.1 mm Hg (P < 0.01). Following smoking, Tgluc decreased from 0.7 +/- 0.1 to 0.6 +/- 0.1 ng/mL (P < 0.01), and Tlact increased from 0.2 +/- 0.1 to 0.3 +/- 0.2 ng/mL (P < 0.01). The observed alterations were similar in smokers and ex-smokers. CONCLUSIONS Nicotine has a limited vasoactive effect in the skin and subcutis unlikely to be explained by smoking, which distinctly decreases tissue blood flow, oxygen tension, and aerobe metabolism independent of smoking status.

The use of cutaneous microdialysis to measure substance P-induced histamine release in intact human skin in vivo

BACKGROUND The purpose of this study was to introduce a microdialysis technique, which makes it possible to measure the release of small inflammatory mediators into the extracellular water space in intact human skin in vivo. Using this technique, we have studied the histamine releasing properties of substance P, a putative skin mast cell releasing agent. METHODS Small hollow fibers were inserted into the upper dermis of nine healthy subjects. Each fiber was perfused with Krebs Ringer bicarbonate buffer at a rate of 3.0 microliters/min. After establishment of a baseline, each fiber was challenged intracutaneously with substance P (0 to 4 mumol/L). Samples were collected at 2-minute intervals for 18 minutes. Histamine was measured by a fluorometric method, which correlated with an enzyme immunoassay (r = 0.96). RESULTS Baseline dialysate histamine concentration was 1.7 +/- 0.3 ng/ml. Peak histamine release after injection of vehicle, 0.5, 1, 2, and 4 mumol/L substance P was 0.0, 1.0, 6.0, 44.5, and 88.5 ng/ml, respectively (p = 0.00002). Statistically significant histamine release was demonstrated with 1.0 mumol/L substance P and greater. Most peak values were seen 2 to 4 minutes after injection. The histamine elimination showed a monoexponential decline; dialysate histamine half-life was 3.81 +/- 0.28 minutes. CONCLUSIONS This study showed that substance P releases histamine in a dose-dependent manner from intact human skin in normal subjects. We suggest that microdialysis may be a promising technique for the evaluation of mediator levels in intact human skin after intradermal injection of an inflammatory or allergenic stimulus.

The toe-brachial index in the diagnosis of peripheral arterial disease

BACKGROUND Peripheral arterial disease (PAD) can be diagnosed noninvasively by segmental blood pressure measurement and calculating an ankle-brachial index (ABI) or toe-brachial index (TBI). The ABI is known to be unreliable in patients with vascular stiffness and fails to detect the early phase of arteriosclerotic development. The toe vessels are less susceptible to vessel stiffness, which makes the TBI useful. However, the diagnostic limits used in guidelines, clinical settings, and experimental studies vary substantially. This review provides an overview of the evidence supporting the clinical use of the TBI. METHODS A review of the literature identified studies reporting the use of the TBI regarding guideline recommendations, normal populations, correlations to angiographic findings, and prognostic implications. RESULTS Eight studies conducted in a normal population were identified, of which only one study used imaging techniques to rule out arterial stenosis. A reference value of 0.71 was estimated as the lowest limit of normal based on the weighted average in studies with preheating of the limbs. A further seven studies showed correlations of the TBI with angiographic findings. The TBI had a sensitivity of 90% to 100% and a specificity of 65% to 100% for the detection of vessel stenosis. Few studies investigated the value of the TBI as a prognostic marker for cardiovascular mortality and morbidity, and no firm conclusions could be made. Studies have, however, shown correlation between the TBI and comorbidities such as kidney disease, diabetes, and microvasculature disease. CONCLUSIONS In contrast to the well-defined and evidence-based limits of the ABI, the diagnostic criteria for a pathologic TBI remain ambiguous. Although several guidelines and reviews of PAD diagnostics recommend a TBI <0.70 as cutoff, it is not strictly evidence-based. The current literature is not sufficient to conclude a specific cutoff as diagnostic for PAD. The current studies in normal populations and the correlation with angiography are sparse, and additional trials are needed to further validate the limits. Large-scale trials are needed to establish the risk of morbidity and mortality for the various diagnostic limits of the TBI.

Different patterns of mast cell activation by muscle relaxants in human skin.

BackgroundActivation of mast cells and systemic release of histamine are major side effects of intravenously administered muscle relaxants. In the current study, dermal microdialysis was used for the investigation of mast cell activation by muscle relaxants. Dermal microdialysis enabled simultaneous assessment of mediator release, vascular reactions, and sensory effects induced by intradermal application of muscle relaxants without systemic side effects. MethodsSuccinylcholine, the isoquinolines cisatracurium, atracurium, and mivacurium, and the steroids pancuronium, vecuronium, rocuronium, and rapacuronium were tested in human volunteers (n = 6 each). After intradermal insertion of microdialysis capillaries (0.4 mm diameter, cutoff 3,000 kd) and a 60-min equilibration period, the muscle relaxants were delivered via the capillaries for 30 min, followed by a 30-min washout period. Dialysate was sampled at 15-min intervals, and histamine, mast cell tryptase, and protein extravasation were determined. Changes in skin blood flow were measured using a laser Doppler imager. Potency and efficacy were derived from nonlinear fittings of the dose–response curves. ResultsFor succinylcholine and the isoquinolines, dose–response curves for the vascular and sensory effects paralleled the histamine and tryptase release. In contrast, aminosteroids evoked a rapid histamine release that was accompanied by a delayed increase in tryptase. ConclusionsDermal microdialysis has been successfully used to simultaneously assess mediator release, vascular reactions, and sensory effects. The different pattern of tryptase release by isoquinolines and aminosteroids suggests different mechanisms of mast cell activation.

Pituitary adenylate cyclase activating polypeptide (PACAP) is localized in human dermal neurons and causes histamine release from skin mast cells

Abstract.Objective and Design: Pituitary adenylate cyclase activating polypeptide (PACAP) is a neuropeptide homologous with vasoactive intestinal polypeptide (VIP) which is known to induce histamine release in human skin mast cells. PACAP has not been detected in human skin. The purposes of the study were to investigate the occurrence of PACAP in human skin and to evaluate the histamine releasing activity of the two common pro-PACAP products, PACAP-27 and PACAP-38.¶Material: Fourteen human surgical skin samples were obtained. PACAP and VIP were visualized by immunohistochemistry. A microdialysis technique was used to measure histamine release in intact skin samples following intradermal injections of the peptides.¶Results: PACAP and VIP were localized in dermal nerves in connection with sweat glands. Intradermal injection of 3 or 10 μm PACAP significantly released histamine. Kinetics of histamine release showed peak release 2–4 min after skin challenge. Ten μm of PACAP-27, VIP and somatostatin caused histamine release with similar efficacy, whereas PACAP-38 was less effective. Substance P was twice as efficient as PACAP-27, whereas calcitonin gene-related peptide did not release histamine.¶Conclusions: PACAP is found in human skin and is capable of releasing histamine from skin mast cells.

Elevated plasma levels of vascular endothelial growth factor and plasminogen activator inhibitor-1 decrease during improvement of psoriasis

Abstract.Objective and Design: An evaluation of angiogenesis related molecules during open treatment of psoriasis.¶Materials and Subjects: Plasma samples and skin biopsies from 16 patients with psoriasis and plasma samples from 13 healthy controls.¶Treatment: Ranitidine 300 mg orally twice daily for 6 months.¶Methods: Vascular endothelial growth factor (VEGF) and plasminogen activator inhibitor-1 (PAI-1) were determined by ELISA methods in plasma collected from the patients before treatment and after 1, 3 and 6 months. Vessel counts were performed in biopsies from affected skin areas taken before treatment and after 3 and 6 months. The results were compared to simultaneous PASI scores.¶Results: Pre-treatment plasma levels of VEGF and PAI-1 were significantly elevated in patients compared with levels in healthy persons (p = 0.02 and p = 0.04, respectively). The plasma levels decreased significantly during treatment (p = 0.03 and p = 0.01, respectively), and the decrease in combined levels correlated with the decrease in PASI score. However, the vessel density in affected skin did not change during treatment.¶Conclusions: Increased pre-treatment levels of VEGF and PAI-1 and decrease during improvement of the disease suggest that the two molecules may play a role in pathogenesis of psoriasis.