The Vitamin D Binding Protein and Inflammatory Injury: A Mediator or Sentinel of Tissue Damage?

Neutrophils are the most abundant type of white blood cell in most mammals including humans. The primary role of these cells is host defense against microbes and clearance of tissue debris in order to facilitate wound healing and tissue regeneration. The recruitment of neutrophils from blood into tissues is a key step in this process and is mediated by numerous different chemoattractants. The neutrophil migratory response is essential for host defense and survival, but excessive tissue accumulation of neutrophils is observed in many inflammatory disorders and strongly correlates with disease pathology. The vitamin D binding protein (DBP) is a circulating multifunctional plasma protein that can significantly enhance the chemotactic activity of neutrophil chemoattractants both in vitro and in vivo. Recent in vivo studies using DBP deficient mice showed that DBP plays a larger and more central role during inflammation since it induces selective recruitment of neutrophils, and this cofactor function is not restricted to C5a, as prior in vitro studies indicated, but can enhance chemotaxis to many chemoattractants. DBP also is an extracellular scavenger for actin released from damaged/dead cells and formation of DBP-actin complexes is an immediate host response to tissue injury. Recent in vitro evidence indicates that DBP bound to G-actin, and not free DBP, functions as an indirect but essential cofactor for neutrophil migration. DBP-actin complexes always will be formed regardless of what initiated an inflammation, since release of actin from damaged cells is a common feature in all types of injury and DBP is abundant and ubiquitous in all extracellular fluids. Indeed, these complexes have been detected in blood and tissue fluids from both humans and experimental animals following various forms of injury. The published data strongly supports the premise that DBP-actin complexes are the functional neutrophil chemotactic cofactor that enhances neutrophil chemotaxis in vitro and augments neutrophilic inflammation in vivo. This review will assess the fundamental role of DBP in neutrophilic inflammation and injury.

Glycyrrhizin attenuates tissue injury and reduces neutrophil accumulation in experimental acute pancreatitis

Leukocyte infiltration and acinar cell injury are characteristic features of acute pancreatitis (AP). However, the signaling pathways regulating inflammation and accumulation of leukocytes into pancreas tissue remains poorly elucidated. In the current study, we investigated the effects of Glycyrrhizin (GZ) on cerulein-induced AP in mice. AP was induced in male C57BL/6 by intraperitoneal injection of 50 μg/kg cerulein hourly, with a total of 7 times. 1 hour after the last injection of cerulean, mice were treated with either 35 or 70 mg/kg of GZ. Serum amylases and lipases were measured using automated chromogenic assay, MCP-1 and MIP-2 concentrations were measured in the serum by ELISA, and the number of infiltrated inflammatory cells in the pancreas were evaluated by flow cytometry. We found that GZ treatment resulted in reduction (i) both amylase and lipase activities, (ii) the serum levels of both MCP-1 and MIP-2; and (iii) markedly attenuated cerulein-induced histopathological alternations and water contents. Furthermore, we observed that GZ significantly decreased the number of infiltrated monocytes and neutrophils into the pancreas tissue. In conclusion, we demonstrate that GZ attenuates AP signs and inhibits inflammatory cell recruitments into pancreas.

A comparative study of the ability of calcitonin gene-related peptide and adrenomedullin(13 - 52) to modulate microvascular but not thermal hyperalgesia responses

Calcitonin gene-related peptide (CGRP), a neuropeptide, is a potent vasodilator. Adrenomedullin (ADM) is suggested to be produced by vascular cells in inflamed tissue. ADM shares some structural homology with CGRP. We have compared the ability of CGRP and ADM to modulate microvascular and thermal hyperalgesic responses in rat skin. Vasodilator activity was assessed by laser Doppler flowmetry, inflammatory oedema by the extravascular accumulation of intravenously-injected labelled albumin, and neutrophil accumulation by tissue myeloperoxidase, in dorsal skin. Hyperalgesia was assessed by a thermal hyperalgesimeter in paw skin. ADM (10-300 pmol) was 3 fold less potent than CGRP (3-100 pmol) as a direct vasodilator. CGRP (30 pmol) potentiated oedema formation induced by mediators of increased microvascular permeability, as expected (P<0.01). However, ADM (30-100 pmol) was without a potentiating effect, although ADM (300 pmol) was effective (P<0.01). By comparison ADM (100 pmol) potentiated neutrophil accumulation induced by interleukin-1beta (P<0.05), whereas CGRP (30 pmol) did not. No thermal hyperalgesia was observed to either CGRP or ADM, when given as single or repeated treatments. Thus despite a dilator activity neither CGRP nor ADM appears to mediate hyperalgesic activity in the periphery. However ADM, like CGRP, has the ability to potentiate inflammatory oedema formation and, in addition, ADM can potentiate neutrophil accumulation. ADM may, as suggested for CGRP, act as a modulator of the vascular phases of inflammation. The property of the two compounds of evoking differential microvascular responses and neutrophil accumulation may be due to differing mechanisms of action.