Epidermal growth factor-induced rapid relaxation of the isolated rabbit mesenteric artery

HB-EGF improves intestinal microcirculation after hemorrhagic shock

BACKGROUND

The goal of this study was to determine the role of heparin-binding epidermal growth factor-like growth factor (HB-EGF) as a mediator of gut microcirculation after hemorrhagic shock and resuscitation (HS/R) in mice.

MATERIALS AND METHODS

HS/R was induced in HB-EGF knockout (KO) and wild type (WT) mice. Ink-gelatin injection and vascular corrosion casting were performed to visualize the gut microvasculature. The degree of gut microcirculatory injury was graded using five patterns of injury (1-5) according to the severity of microvascular hypoperfusion. Statistical analyses were performed using linear mixed models with P < 0.05 considered statistically significant.

RESULTS

HB-EGF KO mice subjected to HS/R had significantly decreased perfusion of the gut microvasculature compared with WT mice subjected to HS/R (P = 0.0001). HB-EGF KO mice subjected to HS/R and treated with exogenous HB-EGF had significantly increased gut microvascular perfusion compared with non-HB-EGF treated KO mice (P = 0.01). Lastly, WT mice subjected to HS/R and treated with HB-EGF had significantly increased gut microvascular perfusion compared with non-HB-EGF-treated WT mice (P = 0.04).

CONCLUSIONS

HB-EGF improves gut microcirculation after HS/R. These findings support the clinical use of HB-EGF in protection of the intestines from disease states associated with intestinal hypoperfusion injury.

Vascular smooth muscle contractility assays for inflammatory and immunological mediators

The blood vessels are one of the important target tissues for the mediators of inflammation and allergy; further cytokines affect them in a number of ways. We review the use of the isolated blood vessel mounted in organ baths as an important source of pharmacological information. While its use in the bioassay of vasoactive substances tends to be replaced with modern analytical techniques, contractility assays are effective to evaluate novel synthetic drugs, generating robust potency and selectivity data about agonists, partial agonists and competitive or insurmountable antagonists. For instance, the human umbilical vein has been used extensively to characterize ligands of the bradykinin B(2) receptors. Isolated vascular segments are live tissues that are intensely reactive, notably with the regulated expression of gene products relevant for inflammation (e.g., the kinin B(1) receptor and inducible nitric oxide synthase). Further, isolated vessels can be adapted as assays of unconventional proteins (cytokines such as interleukin-1, proteases of physiopathological importance, complement-derived anaphylatoxins and recombinant hemoglobin) and to the gene knockout technology. The well known cross-talks between different cell types, e.g., endothelium-muscle and nerve terminal-muscle, can be extended (smooth muscle cell interaction with resident or infiltrating leukocytes and tumor cells). Drug metabolism and distribution problems can be modeled in a useful manner using the organ bath technology, which, for all these reasons, opens a window on an intermediate level of complexity relative to cellular and molecular pharmacology on one hand, and in vivo studies on the other.

Heparin-binding EGF-like growth factor increases intestinal microvascular blood flow in necrotizing enterocolitis

BACKGROUND & AIMS

Necrotizing enterocolitis (NEC) is the most common gastrointestinal emergency in neonates. Although the exact etiology remains unknown, decreased intestinal blood flow is believed to play a critical role. We have shown that heparin-binding epidermal growth factor-like growth factor (HB-EGF) protects the intestines from injury in a rodent model of NEC. Our current goal was to assess the effect of HB-EGF on intestinal microvascular blood flow and intestinal injury in rat pups subjected to experimental NEC.

METHODS

Newborn rat pups were subjected to stress by exposure to hypoxia, hypothermia, hypertonic feedings, and lipopolysaccharide, with some pups receiving HB-EGF (800 microg x kg(-1) x dose(-1)) added to the feeds. Control animals received breast milk. Intestinal injury was graded using a standard histologic injury scoring system. Microvascular blood flow was assessed by fluorescein isothiocyanate/dextran angiography, with fluorescent images subjected to quantification, and by scanning electron microscopy.

RESULTS

Intestinal microvascular blood flow (defined as the extent of vascular filling with fluorescein isothiocyanate/dextran) was significantly decreased in pups subjected to stress compared with breast-fed pups. Stressed pups treated with HB-EGF had significantly increased microvascular blood flow. The changes in villous microvasculature correlated with histologic injury scores, with stressed pups treated with HB-EGF showing decreased histologic injury.

CONCLUSIONS

HB-EGF significantly preserved intestinal microvascular blood flow in pups subjected to experimental NEC, indicating that HB-EGF may play a critical role in the treatment of various diseases manifested by decreased intestinal blood flow, including NEC.

Airway epithelial-derived factor relaxes pulmonary vascular smooth muscle

The factors controlling the pulmonary vascular resistance under physiological conditions are poorly understood. We have previously reported on an apparent cross talk between the airway and adjacent pulmonary arterial bed where a factor likely derived from the bronchial epithelial cells reduced the magnitude of agonist-stimulated force in the vascular smooth muscle. The main purpose of this investigation was to evaluate whether bronchial epithelial cells release a pulmonary arterial smooth muscle relaxant factor. Conditioned media from SPOC-1 or BEAS-2B, a rat- and a human-derived bronchial epithelial cell line, respectively, were utilized. This media significantly relaxed precontracted adult but not fetal pulmonary arterial muscle in an oxygen tension-dependent manner. This response was mediated via soluble guanylate cyclase, involving AKT/PI3-kinase and neuronal nitric oxide synthase. Airway epithelial cell-conditioned media increased AKT phosphorylation in pulmonary smooth muscle cells (SMC) and reduced intracellular calcium change following ATP stimulation to a significantly greater extent than observed for bronchial SMC. The present data strongly support the evidence for bronchial epithelial cells releasing a stable and soluble factor capable of inducing pulmonary arterial SMC relaxation. We speculate that under physiological conditions, the maintenance of a low pulmonary vascular resistance, postnatally, is in part modulated by the airway epithelium.

Heparin-binding EGF-like growth factor preserves mesenteric microcirculatory blood flow and protects against intestinal injury in rats subjected to hemorrhagic shock and resuscitation

BACKGROUND

The gut is highly susceptible to injury after hemorrhagic shock and resuscitation (HS/R) because of progressive mesenteric hypoperfusion. The aim of the current study was to evaluate the effect of heparin-binding EGF-like growth factor (HB-EGF) on mesenteric microcirculatory blood flow and intestinal injury in rats subjected to HS/R.

METHODS

HS/R was induced in adult rats, with some rats receiving HB-EGF (600 mug/kg) IV at the onset of resuscitation (HS/R+HB-EGF) and others receiving vehicle only (HS/R). FITC-dextran was administered intra-arterially to evaluate mesenteric microcirculation, and intestinal damage and restitution were evaluated histologically. Data were expressed as mean +/- SE, with P < .05 considered statistically significant.

RESULTS

Microcirculatory blood flow was significantly reduced 1 hour after HS/R. HS/R+HB-EGF rats had significantly increased microcirculatory flow compared with HS/R rats at 1 hour (4.5 +/- 0.43 vs 2.64 +/- 0.46, P < .05) and 3 hours (8.04 +/- 1.58 vs 2.89 +/- 0.63, P < .05) after HS/R. HS/R+HB-EGF rats had significantly less intestinal damage compared with HS/R rats 3 hours after resuscitation (2.04 +/- 0.5 vs 3.08 +/- 0.5, P < .05), along with significantly fewer incompetent (nonresurfaced, nonhealed) villi, which is indicative of improved restitution.

CONCLUSIONS

HB-EGF significantly improved postresuscitation microcirculatory blood flow in rats subjected to HS/R, associated with significantly decreased intestinal damage and increased restitution. These results suggest that HB-EGF may be a useful therapeutic agent that improves intestinal blood flow in patients with intestinal injury secondary to hemorrhagic shock.