Salivary epidermal growth factor and intestinal adaptation in male and female mice

The role of recombinant epidermal growth factor and serotonin in the stimulation of tumor growth in a SCCHN xenograft model

One challenge of squamous cell carcinoma of the head and neck (SCCHN) chemotherapy is a small percentage of tumor cells that arrest in the G0 phase of the cell cycle and are thus not affected by chemotherapy. This could be one reason for tumor recurrence at a later date. The recruitment of these G0-arresting cells into the active cell cycle and thus, proliferation, may increase the efficacy of chemotherapeutic agents. The aim of this study was to investigate whether stimulation with recombinant epidermal growth factor (EGF) or serotonin leads to an increased tumor cell proliferation in xenografts. Detroit 562 cells were injected into NMRI-Foxn1nu mice. Treatment was performed with 15 µg murine or human EGF, or 200 µg serotonin. The control mice were treated with Lactated Ringer's solution (5 mice/group). Tumor size was measured on days 4, 8 and 12 after tumor cell injection. The EGF stimulated mice showed a significantly higher tumor growth compared to the serotonin-stimulated mice and the untreated controls. In the present study, we show that it is possible to stimulate tumor cells in xenografts by EGF and thus, enhance cell proliferation, resulting in a higher tumor growth compared to the untreated control group. In our future investigations, we plan to include a higher number of mice, an adjustment of the EGF dosage and cell subanalysis, considering the heterogeneity of SCCHN tumors.

Chronic pharmacologic inhibition of EGFR leads to cardiac dysfunction in C57BL/6J mice

Molecule-targeted therapies like those against the epidermal growth factor receptor (EGFR) are becoming widely used in the oncology clinic. With improvements in treatment efficacy, many cancers are being treated as chronic diseases, with patients having prolonged exposure to several therapies that were previously only given acutely. The consequence of chronic suppression of EGFR activity may lead to unexpected toxicities like altered cardiac physiology, a common organ site for adverse drug effects. To explore this possibility, we treated C57BL/6J (B6) mice with two EGFR small molecule tyrosine kinase inhibitors (TKIs), irreversible EKB-569 and reversible AG-1478, orally for 3 months. In B6 female mice, chronic exposure to both TKIs depressed body weight gain and caused significant changes in left ventricular (LV) wall thickness and cardiac function. No significant differences were observed in heart weight or cardiomyocyte size but histological analysis revealed an increase in fibrosis and in the numbers of TUNEL-positive cells in the hearts from treated female mice. Consistent with histological results, LV apoptotic gene expression was altered, with significant downregulation of the anti-apoptotic gene Bcl2l1. Although there were no significant differences in any of these endpoints in treated male mice, suggesting sex may influence susceptibility to TKI mediated toxicity, the LVs of treated male mice had significant upregulation of Egf, Erbb2 and Nppb over controls. Taken together, these data suggest that chronic dietary exposure to TKIs may result in pathological and physiological changes in the heart.

Critical roles for EGF receptor signaling during resection-induced intestinal adaptation

The adaptation response of the remnant gut to massive intestinal resection represents a mitogenic signal involving all bowel wall layers. In the mucosa, this response results in taller villi, deeper crypts, and enhanced enterocyte turnover as gauged by greater rates of both proliferation and apoptosis. Although the exact mechanisms and mediators of this important compensatory response remain incompletely understood, work from this laboratory over the past decade has illuminated a crucial role for intact receptor signaling for a robust response. Using a murine model for intestinal resection, transgenic, null and mutant mouse strains have provided unique experimental paradigms to dissect molecular mechanisms for epidermal growth factor (EGF) receptor-directed influence on adaptation. Stimulation of this receptor is linked with a magnified adaptation response, whereas attenuation of the activity of this receptor is associated with impaired adaptation. EGF receptor activation and expression are both elevated in enterocytes after resection, and salivary levels of EGF-the major ligand for the EGF receptor-are increased. In addition to stimulation of enterocyte proliferation, EGF receptor signaling prevents the typical increase in rates of enterocyte apoptosis, probably by affecting the ratio of expression of both pro- and anti-apoptotic Bcl-2 family members. The key to optimizing care for patients with short gut syndrome will necessarily follow a thorough understanding of intestinal adaptation responses.

Role of epidermal growth factor in the pathogenesis of neonatal necrotizing enterocolitis

Neonatal necrotizing enterocolitis (NEC) is an increasingly frequent condition encountered in premature infants for which the etiology is not well understood. Epidermal growth factor (EGF) is abundant in many fluids bathing the fetal and neonatal gastrointestinal tract, including amniotic fluid, saliva, and breast milk. EGF is acknowledged to be important for normal intestinal development as well as repair following injury to the gastrointestinal mucosa. There appears to be mounting evidence to support a possible link between deficient EGF production and the development of NEC. The relevant evidence for the role of EGF in intestinal development and mucosal repair, as well as its potential involvement in the genesis of NEC will be reviewed.

Association of EGF polymorphism with schizophrenia in Finnish men

Some recent data suggest that epidermal growth factor (EGF) protein levels are altered in the brain of schizophrenic patients. In addition, a novel polymorphism of the EGF gene is associated with enhanced production of EGF in vitro. We conducted a retrospective study to explore the impact of EGF polymorphism on factors associated with schizophrenia. The sample consisted of 94 patients with schizophrenia who had either responded to treatment with conventional neuroleptics or who were considered non-responders. The control sample consisted of 98 blood donors. In our sample, the G allele was associated with schizophrenia in male patients (OR = 3.594 (95% CI 1.347-9.591), p = 0.008). The G allele was also associated with a later age at onset in male patients with schizophrenia. However, no association was found between treatment response and EGF polymorphism.

Sex- and age-related temporal variations in intestinal-epithelium proliferation in the suckling mouse

Intestinal-crypt enterocytes are a cell population undergoing constant renewal in the mouse. Both adult and 28 d old animals have been shown to exhibit circadian rhythms in cell proliferative indices, but there are only scant data on the 24 h mitotic activity in the small and large intestine of younger mice. The present studies were thus undertaken in order to characterize the proliferative pattern of enterocytes in the duodenum and colon of 7 and 14 d old males and females of the C3H/S strain. Animals of each sex and from each age group were sacrificed every 4h during a 24 h span, with each animal receiving an injection of colchicine 4h before sacrifice. Samples of duodenum and colon were removed and processed for hematoxylin-eosin staining. Twenty longitudinally sectioned crypts within each sample were analyzed, and the mitotic indices of both cell populations from each animal were estimated. The arithmetic mean +/- SEM for each experimental group were then calculated and the statistical significance of differences between the means assessed by ANOVA and Student t-tests. We observed a greater daily mitotic activity in the duodenum than the colon, and moreover enterocytic proliferation in both those regions was greater in 14 than 7 d old animals. Twenty-four hour variations in mitotic activity occurred in all the experimental groups and tissues except for the large intestine of 7 d old females. Finally, the temporal profile of epithelium proliferation in the suckling mouse varied with age, sex, and site of the intestine studied.

Targeted inactivation of the mouse guanylin gene results in altered dynamics of colonic epithelial proliferation

Heat-stable enterotoxin (STa), elaborated by enterotoxigenic Echerichia coli, is a worldwide cause of secretory diarrhea in infants and travelers. Both STa and guanylin, a peptide structurally similar to STa, increase intracellular cGMP levels after binding to the same intestinal receptor, guanylate cyclase C (GC-C). Distinct from its role as an intestinal secretagogue, guanylin may also have a role in intestinal proliferation, as guanylin expression is lost in intestinal adenomas. To determine the function of guanylin in intestinal epithelia, guanylin null mice were generated using a Cre/loxP-based targeting vector. Guanylin null mice grew normally, were fertile and showed no signs of malabsorption. However, the levels of cGMP in colonic mucosa of guanylin null mice were significantly reduced. The colonic epithelial cell migration rate was increased and increased numbers of colonocytes expressing proliferating cell nuclear antigen (PCNA) were present in crypts of guanylin null mice as well. The apoptotic index was similar in guanylin null mice and littermate controls. We conclude from these studies that loss of guanylin results in increased proliferation of colonic epithelia. We speculate that the increase in colonocyte number is related to decreased levels of cGMP and that this increase in proliferation plays a role in susceptibility to intestinal adenoma formation and/or progression.

Associations between age or sex and prevalence of gastric ulceration in Standardbred racehorses in training

OBJECTIVE

To determine associations between age, sex, or medical treatment and prevalence and severity of gastric ulceration in Standardbred racehorses in training.

DESIGN

Cross-sectional study.

ANIMALS

224 Standardbred racehorses in training.

PROCEDURE

Gastroscopy was performed on each horse, and mucosal ulceration was graded from 0 (normal mucosa, no lesions) to 3 (extensive, often coalescing, lesions with areas of deep ulceration). Associations between age, sex, or treatment and prevalence and severity of ulcers were evaluated.

RESULTS

Prevalence of gastric ulceration was 87%. Although there was little association between age and prevalence of ulcers, there was an association between age and severity of ulcers. Most 2-year-old horses (57.7%) had an ulcer score of 0 or 1. In all other age groups, most (58% to 82.61%) of horses had an ulcer score of 2 or 3. Although overall prevalence of ulceration was comparable among sex groups, the relative risk for gastric ulceration increased with age in castrated males, whereas it decreased in females and sexually intact males.

CONCLUSIONS AND CLINICAL RELEVANCE

Gastric ulceration is common in Standardbred horses in race training. Severity is higher in horses > or = 3 years of age than in 2-year-old horses. Relative risk for ulceration increases with age in castrated males.

Intestinal adaptation: structure, function, and regulation

After massive small bowel resection (SBR), the remnant intestine undergoes an adaptive process characterized by increases in wet weight, protein and DNA content, villus height and crypt depth, and absorptive surface area. These changes are the result of a proliferative stimulus that increases crypt cell mitosis and augments cellular progression along the villus axis. Functionally, there is upregulation of the Na(+)/glucose cotransporter, Na(+)/H(+) exchanger, and other enzymes involved in intestinal digestion and absorption. These physiologic events are a compensatory response to the sudden loss of digestive and absorptive capacity by the remnant intestine. A major consequence of inadequate intestinal adaptation is lifelong dependence on parenteral nutrition, which results ultimately in cholestatic liver dysfunction. Furthermore, adaptation may be associated with changes in intestinal permeability and an increased risk of bacterial translocation and sepsis. Several mediators thought to be integral to the postresection adaptive response have been proposed, including luminal nutrients, gastrointestinal secretions, and humoral factors. A thorough understanding of intestinal adaptation will be essential in the rational development of new and innovative therapies that amplify this complex but important process.

cDNA microarray analysis of adapting bowel after intestinal resection

BACKGROUND/PURPOSE

Studies of the genetic regulation of various physiologic processes have been hampered by methodologies that are limited to the analysis of individual genes. The advent of cDNA microarray technology has permitted the simultaneous screening of numerous genes for alterations in expression. In this study, cDNA microarrays were used to evaluate gene expression changes during the intestinal adaptive response to massive small bowel resection (SBR).

METHODS

Male ICR mice (n = 20) underwent either a 50% SBR or sham operation and then were given either orogastric epidermal growth factor (EGF, 50 microg/kg/d) or saline. After 3 days, cDNA microarray analysis was performed on mRNA extracted from the remnant ileum.

RESULTS

From over 8,700 different genes, the array identified 27 genes that were altered 2-fold or greater after SBR. Small proline-rich protein 2 (sprr2), the gene with the greatest expression change (4.9-fold), was further upregulated by EGF. This gene has never been characterized in the intestine or described in intestinal adaptation.

CONCLUSIONS

cDNA microarray analysis showed enhanced expression of sprr2, a gene not previously known to be involved in the physiology of adaptation after SBR. This technology provides a more rapid and efficient means of dissecting the complex genetic regulation of gut adaptation.