Bradykinin causes a prolonged increase in skin microvascular permeability

Emerging Roles of Mast Cells in the Regulation of Lymphatic Immuno-Physiology

Mast cells (MCs) are abundant in almost all vascularized tissues. Furthermore, their anatomical proximity to lymphatic vessels and their ability to synthesize, store and release a large array of inflammatory and vasoactive mediators emphasize their significance in the regulation of the lymphatic vascular functions. As a major secretory cell of the innate immune system, MCs maintain their steady-state granule release under normal physiological conditions; however, the inflammatory response potentiates their ability to synthesize and secrete these mediators. Activation of MCs in response to inflammatory signals can trigger adaptive immune responses by dendritic cell-directed T cell activation. In addition, through the secretion of various mediators, cytokines and growth factors, MCs not only facilitate interaction and migration of immune cells, but also influence lymphatic permeability, contractility, and vascular remodeling as well as immune cell trafficking through the lymphatic vessels. In summary, the consequences of these events directly affect the lymphatic niche, influencing inflammation at multiple levels. In this review, we have summarized the recent advancements in our understanding of the MC biology in the context of the lymphatic vascular system. We have further highlighted the MC-lymphatic interaction axis from the standpoint of the tumor microenvironment.

Potentiation of ATP- and bradykinin-induced [Ca2+]c responses by PTHrP peptides in the HaCaT cell line

In the epidermis, local and systemic factors including extracellular nucleotides and parathyroid hormone-related protein (PTHrP) regulate keratinocyte proliferation and differentiation. Extracellular nucleotides increase proliferation via activation of P2 receptors and induction of calcium transients, while endoproteases cleave PTHrP, resulting in fragments with different cellular functions. We investigated the effects of adenosine 5'-triphosphate (ATP) alone and in combination with synthetic PTHrP peptides on calcium transients in HaCaT cells. ATP induced calcium transients, while PTHrP peptides did not. C-terminal and mid-molecule PTHrP peptides (1-100 pM) potentiated ATP-induced calcium transients independently of calcium influx. 3-Isobutyl-1-methylxanthine potentiated ATP-induced calcium transients, suggesting that a cyclic monophosphate is responsible. Cyclic AMP is not involved, but cyclic GMP is a likely candidate since the protein kinase G inhibitor, KT5823, inhibited potentiation. Co-stimulation with ATP and either PTHrP (43-52) or PTHrP (70-77) increased proliferation, suggesting that this is important in the regulation of cell turnover and wound healing and may be a mechanism for hyperproliferation in skin disorders such as psoriasis. Finally, PTHrP fragments potentiated bradykinin-induced calcium transients, suggesting a role in inflammation in the skin. Since PTHrP is found in many normal and malignant cells, potentiation is likely to have a wider role in modulating signal transduction events.

Bradykinin- and thrombin-induced increases in endothelial permeability occur independently of phospholipase C but require protein kinase C activation

We determined whether activation of phosphatidylinositol-specific phospholipase C (PI-PLC) and a subsequent increase in cytosolic calcium concentration ([Ca2+]i) was an obligatory signaling event mediating the increase in transendothelial permeability induced by bradykinin (BK) and alpha-thrombin (alpha-T). Both BK and alpha-T (each at a concentration range of 0.01-1 microM) caused dose-dependent increases in transendothelial 125I-albumin permeability in cultured bovine pulmonary artery endothelial cell monolayers. Both agonists also produced a rise in inositol (1,4,5)-trisphosphate [Ins(1,4,5)P3] by 10 sec that was followed by a prolonged increase in [Ca2+]i. Pretreatment of endothelial cells with the PLC inhibitor, 1-(6-((17 beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1 H-pyrrole-2,5-dion [(U73122) at 10 microM for 15 min], prevented the increases in Ins(1,4,5)P3 and [Ca2+]i induced by both BK and alpha-T. However, inhibition of PLC with U73122 or another PLC inhibitor, neomycin, did not prevent the increase in endothelial permeability induced by either agonist. In contrast, depletion of cellular protein kinase C (PKC) with phorbol-12-myristate 13-acetate (0.01 microM for 20 hr) increased both BK- and alpha-T-induced phosphoinositide turnover but inhibited the agonist-induced increase in permeability. A PKC inhibitor, staurosporine (5 microM) likewise inhibited the BK-induced increase in endothelial cell permeability to albumin. We conclude that increases in endothelial permeability induced by the inflammatory mediators, BK and thrombin, can occur independently of PLC activation and increased [Ca2+]i but that a PKC-dependent pathway is required for the permeability response.

Acute stimulation of glucose transport by histamine in cardiac microvascular endothelial cells

The purpose of the present work was to study the acute regulation of glucose uptake in cultured cardiac endothelial cells (CEC). Two types of potential stimuli were considered: (1) agents that are known to acutely stimulate glucose transport (i.e., within minutes) in fat and muscle tissues and (2) agents that influence endothelial cell function. Among the former agents, neither insulin, nor catecholamines (adrenaline, dopamine, phenylephrine), nor serotonin affected the rate of glucose transport in CEC, while SH-group reagents (phenylarsine oxide, diamide or menadione) were inhibitory. Among the factors of the second group that were tested (heparin, ADP, histamine, bradykinin), histamine was found to stimulate glucose transport in CEC by 10-50%. This effect was concentration-dependent (with an EC50 value approximately equal to 12 microM) and reached a maximum within 5 min upon histamine addition. This stimulation of glucose transport was suppressed by pyrilamine (100 nM), a specific H1-receptor antagonist, but not by cimetidine (100 microM), a H2-selective antagonist. Northern blot and Western blot analysis of CEC extracts revealed the presence of the ubiquitous glucose transporter isoform GLUT1 mRNA and protein, but not of the 'insulin-regulatable' isoform GLUT4. In conclusion, this is the first report on an acute stimulation of glucose transport in cardiac endothelial cells, in particular, and in an insulin-unresponsive cell type, in general. The effect of histamine is most likely mediated by H1-receptors and cannot be accounted for by a recruitment of GLUT4.

Beneficial effects of a bradykinin antagonist in a model of gram-negative sepsis

Activation of the kallikrein-kinin system in sepsis has long been recognized, but its role, beneficial or pathologic, has not been determined. Recently, however, specific bradykinin (BK) antagonists have become available and we sought to determine the effects of a BK antagonist, NPC17731, in a model of sepsis-induced acute lung injury (ALI).

METHODS

Anesthetized swine were studied for 5 hours, receiving a 1-hour infusion of saline (Controls) or live Pseudomonas aeruginosa (Septic untreated). Treatment groups received a 5 mg/kg bolus of NPC17731 followed by a 1 mg/kg bolus hourly commencing either just before sepsis (Pretreatment) or 30 minutes following the onset of sepsis (Posttreatment).

RESULTS

Septic untreated animals showed a rapid, progressive decline in arterial PaO2 compared to controls, and this was significantly improved in both treatment groups. Bronchoalveolar lavage at 5 hours in both treatment groups also showed significant decreases in neutrophil (PMN) counts and protein content compared to untreated septic animals, indicating decreased PMN migration and alveolar-capillary membrane damage. Both treatment groups also showed reduced PMN sequestration in the lung compared to untreated animals, although PMNs did exhibit significant upregulation of PMN CD18 receptor expression and superoxide generation.

CONCLUSIONS

These data imply a significant role for BK in the pathogenesis of sepsis-induced ALI. Use of a competitive BK antagonist significantly attenuated the development of ALI without inhibiting PMN activation. BK antagonists may be a useful adjunct in the armamentarium against sepsis-induced ALI.

Hemodynamic effects of bradykinin antagonism in porcine gram-negative sepsis

Activation of the kallikrein-kinin system in sepsis has long been recognized, but its role, beneficial or pathologic, has not been defined. Recently, however, specific bradykinin (BK) antagonists have become available and this study investigated the effects of a BK antagonist, NPC17731 (Scios-Nova) on systemic and pulmonary hemodynamics in a model of gram-negative sepsis. Anesthetized swine were studied for 5 h receiving a 1-h infusion of saline (controls, group 1, N = 8) or live Pseudomonas aeruginosa (septic, group 2, N = 8). Group 3 (treatment, N = 6) received NPC17731 (5 mg/kg initial bolus followed by 1 mg/kg hourly) just prior to the onset of sepsis. Group 2 animals showed a rapid decrease in systemic arterial pressure (SAP) from 30 min onward, and sustained significant hypotension from 2 h onward. In group 3, SAP fell similarly until 2 h then progressively rose, returning to baseline levels by 5 h. In contrast, cardiac index fell progressively from 3 h onward in groups 2 and 3. Systemic vascular resistance index (SVRI) fell significantly by 2 h in group 2 animals, recovering to baseline by 5 h. Group 3 showed a similar initial fall followed by a rebound increase in SVRI, which, at 5 h was significantly raised above the other groups. Group 2 developed significant, persistent pulmonary artery hypertension which was not reduced by NPC17731. The data imply a significant role for bradykinin in the pathogenesis of hypotension in septic shock in this model. Septic shock was reversed by a BK antagonist which increased peripheral resistance without affecting cardiac output.(ABSTRACT TRUNCATED AT 250 WORDS)

Bradykinin induces phosphoinositide turnover, 1,2-diglyceride formation, and growth in cultured adult human keratinocytes

The effects of bradykinin on activation of phosphoinositide turnover, 1,2-diglyceride formation, and growth of cultured adult human keratinocytes were investigated. Keratinocytes specifically bound [3H]bradykinin with high affinity (kd = 3.4 nM) and displayed 1.5 X 10(5) binding sites/cell. Bradykinin caused a rapid dose-dependent increase in inositol trisphosphate (IP3) inositol bisphosphate, and inositol monophosphate. IP3 was maximally increased (fivefold) at 30 s and remained elevated for at least 10 min. Half maximal stimulation of IP3 formation was observed at 27 nM bradykinin. IP3 accumulation was equally elevated by bradykinin and lys-bradykinin but was not stimulated by des-Arg9-bradykinin, indicating that phospholipase C in cultured keratinocytes is coupled to B2 bradykinin receptors. Treatment of keratinocytes with active phorbol ester (TPA) caused a significant inhibition (50%) of bradykinin-induced IP3 accumulation, suggesting negative regulation of phospholipase C by protein kinase C. Bradykinin also caused a significant elevation in 1,2-diacylglycerol (DAG) content. DAG content was maximally elevated (twofold) at 1 min and remained elevated for at least 10 min. Bradykinin also caused a significant (twofold, p less than 0.02) increase in keratinocyte growth. These data demonstrate that bradykinin is a potent agonist of the phospholipase C/protein kinase C signal transduction system in cultured adult human keratinocytes and that activation of this pathway by bradykinin is associated with increased keratinocyte growth.

Kallikrein messenger RNA in rat arteries and veins

Glandular kallikrein (EC 3.4.21.8) belongs to a subgroup of serine proteases coded by a multigene family. A kininogenase resembling glandular kallikrein has been identified in vascular tissue; however, it is not clear whether it is synthesized by vascular tissue or taken up from plasma. To determine the potential for kallikrein synthesis in vascular tissues, we tested whether messenger RNA (mRNA) for glandular kallikrein is present in rat arteries and veins. Poly(A+) RNA was isolated from pools of arteries or veins (n = 3, 30 rats each). Poly(A+) RNA from the kidney and liver was used as a positive and negative control, respectively. As a probe, we used rat pancreatic kallikrein 32P-labeled complementary DNA, which recognizes mRNA of the entire rat kallikrein family. Slot-blot analysis indicated that kallikrein mRNA was present in mRNA from the arteries, veins, and kidney but not from the liver. Poly(A+) RNA from arteries and veins contained approximately 1% as much kallikrein mRNA as that from the kidney. To confirm the slot-blot results and determine whether the mRNA for true glandular kallikrein was present in vascular tissue, we employed a polymerase chain reaction assay, first using primers specific for the entire kallikrein family (which amplify a 430-bp fragment) and then using primers specific for true glandular kallikrein mRNA (which amplify a 370-bp fragment). After the polymerase chain reaction assay, both arteries and veins showed fragments of these sizes when tested with rat kallikrein complementary DNA probe, thus confirming the presence of glandular kallikrein mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Hypothermia prevents increased capillary permeability following ischemia-reperfusion injury

Severely injured trauma victims are frequently hypothermic. It is unclear, however, whether hypothermia itself is a detrimental or protective physiologic response to injury. One of the major consequences of fluid resuscitation following ischemic injury is edema formation, characterized by ischemia-reperfusion injury models. The purpose of this study was to examine the effect of regional hypothermia on a feline intestinal model of ischemia-reperfusion injury. An autoperfused segment of cat ileum was isolated and arterial, venous, and lymphatic vessels were cannulated. Lymph flow (Q1), lymph (C1), and plasma (Cp) protein concentrations and segmental blood flow (Qb) were measured. Permeability changes were characterized by the minimal C1/Cp ratio obtained by elevating venous outflow pressure. Animals were divided into the following groups: Group I: 1 hr of intestinal ischemia (30 mm Hg) with autoreperfusion; Group II: 1 hr of intestinal hypothermia (28 degrees C) with subsequent rewarming; Group III: 1 hr of combined ischemia and hypothermia. Group III animals were either kept hypothermic (IIIA) or rewarmed (IIIB) during autoreperfusion. Minimal C1/Cp ratios (mean +/- SEM) were as follows:

CONTROL

0.15 +/- 0.02; Group I*: 0.32 +/- 0.03; Group II: 0.15 +/- 0.01; Group IIIA: 0.18 +/- 0.02; Group IIIB*: 0.42 +/- 0.02; (* = P less than 0.01 vs control). Reperfusion flow rates were no different between Group IIIA and Group IIIB animals. Ischemia-reperfusion, but not hypothermia alone, caused a marked increase in intestinal capillary permeability. Permeability increased after combined ischemia and hypothermia only if reperfusion was accompanied by rewarming. Hypothermic reperfusion protected against the increased permeability following ischemia.

Experimental methods in the pathogenesis of limb ischemia

Ischemia of extremities is responsible for considerable morbidity and mortality and the pathophysiology of this condition warrants further study. The purpose of this review is to discuss techniques used in the evaluation of limb ischemia and reperfusion. It is of critical importance to study limb blood flow distribution to the microcirculation where nutritive exchange occurs. Skeletal muscle ischemia progresses to infarction when critical deficits of cellular metabolites develop, which mandates that studies be focused at the cellular level. It is clear that the adverse effects of ischemia can be exacerbated by a reperfusion injury to the endothelium of the microvasculature. Investigators wishing to study limb ischemia have a wide spectrum of methodology and established models available to use in improving the understanding of the complex events of ischemic injury.