Nikunj K. Chokshi

The Role of Nitric Oxide in Intestinal Epithelial Injury and Restitution in Neonatal Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is the most common life-threatening gastrointestinal disease encountered in the premature infant. Although the inciting events leading to NEC remain elusive, various risk factors, including prematurity, hypoxemia, formula feeding, and intestinal ischemia, have been implicated in the pathogenesis of NEC. Data from our laboratory and others suggest that NEC evolves from disruption of the intestinal epithelial barrier, as a result of a combination of local and systemic insults. We postulate that nitric oxide (NO), an important second messenger and inflammatory mediator, plays a key role in intestinal barrier failure seen in NEC. Nitric oxide and its reactive nitrogen derivative, peroxynitrite, may affect gut barrier permeability by inducing enterocyte apoptosis (programmed cell death) and necrosis, or by altering tight junctions or gap junctions that normally play a key role in maintaining epithelial monolayer integrity. Intrinsic mechanisms that serve to restore monolayer integrity following epithelial injury include enterocyte proliferation, epithelial restitution via enterocyte migration, and re-establishment of cell contacts. This review focuses on the biology of NO and the mechanisms by which it promotes epithelial injury while concurrently disrupting the intrinsic repair mechanisms.

Enterobacter sakazakii Enhances Epithelial Cell Injury by Inducing Apoptosis in a Rat Model of Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is an inflammatory intestinal disorder that affects 2%-5% of all premature infants. Enterobacter sakazakii, a common contaminant of milk-based powdered infant formula, has been implicated as a causative agent of sepsis, meningitis, and NEC in newborn infants, with high mortality rates. However, the role played by E. sakazakii in the pathogenesis of NEC is, to date, not known. Here, we demonstrate for the first time that E. sakazakii can induce clinical and histological NEC in newborn rats. E. sakazakii was found to bind to enterocytes in rat pups at the tips of villi and to intestinal epithelial cells (IEC-6) in culture, with no significant invasion. Exposure to E. sakazakii induced apoptosis and increased the production of interleukin-6 in IEC-6 cells and in the animal model. These data suggest that E. sakazakii could be a potential pathogen that induces NEC and triggers intestinal disease by modulating enterocyte intracellular signaling pathways.

Evidence vs experience in the surgical management of necrotizing enterocolitis and focal intestinal perforation.

Introduction:Necrotizing enterocolitis (NEC) and focal intestinal perforation (FIP) are neonatal intestinal emergencies that affect premature infants. Although most cases of early NEC can be successfully managed with medical therapy, prompt surgical intervention is often required for advanced or perforated NEC and FIP.Methods:The surgical management and treatment of FIP and NEC are discussed on the basis of literature review and our personal experience.Results:Surgical options are diverse, and include peritoneal drainage, laparotomy with diverting ostomy alone, laparotomy with intestinal resection and primary anastomosis or stoma creation, with or without second-look procedures.Conclusions:The optimal surgical therapy for FIP and NEC begins with prompt diagnosis and adequate fluid resuscitation. It appears that there is no significant difference in patient outcome based on surgical management alone. However, the infants weight, comorbidities, surgeon preference and timing of intervention should be taken into account before operative intervention.

Role of interleukin-10 in the pathogenesis of necrotizing enterocolitis

BACKGROUND Necrotizing enterocolitis (NEC) is the most common gastrointestinal emergency in premature neonates. The pathogenesis of NEC is characterized by an intestinal epithelial injury caused by perinatal insults, leading to the activation of the mucosal innate immune system and exacerbation of the epithelial barrier damage. Cytokines play an important role in mucosal immunity. Interleukin-10 (IL-10) is an anti-inflammatory cytokine that has been shown to play a role in epithelial integrity and modulation of the mucosal immune system. We hypothesized that IL-10 may protect against the development of experimental NEC by blunting the inflammatory response in the intestine. METHODS Wild-type and IL-10 -/- mice underwent a NEC-inducing regimen of formula feeding in combination with hypoxia and hypothermia (FF+HH). Integrity of the gut barrier was assessed through measurement of epithelial apoptosis, tight junction disruption, and inducible nitric oxide synthase. A total of 5 μg of exogenous IL-10 was administered intraperitoneally to IL-10-/-mouse pups before the initiation of FF+HH to test dependence of gene knockout phenotype on IL-10. RESULTS IL-10 -/- FF+HH showed more severe morphologic and histologic changes compared with controls as evidenced by increased epithelial apoptosis, decreased junctional adhesion molecule-1 localization, and increased intestinal inducible nitric oxide synthase expression. Administration of exogenous IL-10 alleviated the mucosal injury. CONCLUSIONS We conclude that IL-10 plays a protective role in the pathogenesis of NEC by attenuating the degree of intestinal inflammation.

Necrotizing enterocolitis--bench to bedside: novel and emerging strategies.

Necrotizing enterocolitis (NEC) is a devastating illness that predominantly affects premature neonates. The mortality associated with this disease has changed very little during the last two decades. Neonates with NEC fall into two categories: those who respond to medical management alone and those who require surgical treatment. The disease distribution may be focal, multifocal, or panintestinal. Surgical treatment should therefore be based on disease presentation. Recent studies have added significant insight into our understanding of the pathogenesis of NEC. Several groups have shown that upregulation of nitric oxide plays an integral role in the development of epithelial injury in NEC. As a result, some treatment strategies have been aimed at abrogating the toxic effects of nitric oxide. In addition, several investigators have reported the cytoprotective effect of epidermal growth factor, which is found in high levels in breast milk, on the intestinal epithelium. Thus, fortification of infant formula with specific growth factors could soon become a preferred strategy to accelerate intestinal maturation in the premature neonate to prevent the development of NEC. One of the most devastating complications of NEC is the development of short bowel syndrome (SBS). The current treatment of SBS involves intestinal lengthening procedures or bowel transplantation. A novel emerging method for treating SBS involves the use of tissue-engineered intestine. In laboratory animals, tissue-engineered small intestine has been shown to be successful in treating intestinal failure. This article examines recent data regarding surgical treatment options for NEC as well as emerging treatment modalities.

Laparoscopic Choledochal Cyst Excision: Lessons Learned in Our Experience

BACKGROUND Choledochal cyst (CDC) is a rare biliary disorder. Surgical treatment consists of CDC excision and biliary-enteric reconstruction. Recently, some institutions have reported successful CDC excision by using minimally invasive techniques. In this study, we report our experience with the laparoscopic management of CDC, with a focus on key operative maneuvers that enhance the likelihood of successful excision. METHODS Following institutional review board approval, we performed a retrospective review of patients who underwent the laparoscopic excision of CDC and Roux-en-Y hepaticojejunostomy. Between October 2003 and November 2007, we performed laparoscopic CDC excision in 9 patients (8 female and 1 male). Median age was 4 years (range, 8 months to 16 years). There were 7 type I and 2 type IV cysts, according to Todanis classification. Average cyst size was 4.4 cm (range, 1.3-8.5). The procedures were performed by utilizing four or five trochars. RESULTS Six of 9 children presented with preoperative pancreatitis, 1 with abdominal pain, 1 with jaundice, and 1 was found incidentally. Three patients required the conversion to laparotomy due to dense adhesions, secondary to pancreatitis. Six patients underwent successful laparoscopic procedures, 5 had complete cyst excisions, and 1 underwent a proximal excision with distal mucosectomy. Of the 3 patients who required conversion, 2 underwent complete excisions; the other underwent a proximal excision, distal mucosectomy. There were no intraoperative complications. One patient had a postoperative bile leak that required an open hepaticojejunostomy revision. Eight patients had an uneventful recovery. Oral feedings were resumed within an average of 3.4 days (range, 2-9). Average time to discharge was 6.1 days (range, 5-12). Average follow-up time was 18 months (range, 4-48). No further laboratory abnormalities were detected in any of the patients. CONCLUSIONS Laparoscopic resection of CDC and Roux-en-Y hepaticojejunostomy in children is an excellent treatment option. Preoperative pancreatitis may cause increased technical difficulty, necessitating a conversion. Proximal excision with distal mucosectomy

Thoracoscopic Repair of Neonatal Diaphragmatic Hernia

INTRODUCTION The use of minimally invasive surgery (MIS) in the neonatal population is increasing. Thoracoscopic intervention for congenital diaphragmatic hernia (CDH) is no exception. In this report, we describe our initial experience with thoracoscopic repair of left-sided diaphragmatic defects in neonates. MATERIALS AND METHODS We performed retrospective chart reviews on all neonates who underwent thoracoscopic repair of CDH between November 2004 and January 2008. Neonates that underwent thoracoscopic repair were physiologically stable with resolved pulmonary hypertension and minimal to moderate ventilatory support. They had no associated cardiac anomalies. RESULTS We identified 15 neonates with CDH who underwent thoracoscopic repair during the study period. Ten neonates underwent primary repair of the diaphragmatic defect. Five neonates with large defects required closure with a synthetic patch, which was placed thoracoscopically. The average operating room time was 134 minutes. There were no instances of intraoperative respiratory or cardiac instability. Three patients had a recurrence. One recurrence was seen after thoracoscopic patch repair. Two recurrences occurred following primary repair of left diaphragmatic hernias. There were no deaths. Follow-up has been 4-40 months. CONCLUSIONS Neonatal MIS for CDH should be limited to stable patients. The ideal candidate is the newborn without associated anomalies, not requiring extracorporeal membrane oxygenation, on minimal ventilatory support, and without evidence of pulmonary hypertension. It is technically possible to perform thoracoscopic repair with a patch.

P-glycoprotein induction by breast milk attenuates intestinal inflammation in experimental necrotizing enterocolitis

P-glycoprotein (Pgp), a product of the multi-drug resistance gene MDR1a, is a broad specificity efflux ATP cassette transmembrane transporter that is predominantly expressed in epithelial tissues. Because mdr1a−/− mice tend to develop spontaneous colitis in bacteria-dependent manner, Pgp is believed to have a role in protection of the intestinal epithelium from luminal bacteria. Here we demonstrate that levels of Pgp in the small intestine of newborn rodents dramatically increase during breastfeeding, but not during formula feeding (FF). In rats and mice, levels of intestinal Pgp peak on days 3–7 and 1–5 of breastfeeding, respectively. The mdr1a−/− neonatal mice subjected to FF, hypoxia, and hypothermia have significantly higher incidence and pathology, as well as significantly earlier onset of necrotizing enterocolitis (NEC) than congenic wild type mice. Breast-fed mdr1a−/− neonatal mice are also more susceptible to intestinal damage caused by the opportunistic pathogen Cronobacter sakazakii that has been associated with hospital outbreaks of NEC. Breast milk, but not formula, induces Pgp expression in enterocyte cell lines in a dose- and time-dependent manner. High levels of ectopically expressed Pgp protect epithelial cells in vitro from apoptosis induced by C. sakazakii. Taken together, these results show that breast milk-induced expression of Pgp may have a role in the protection of the neonatal intestinal epithelium from injury associated with nascent bacterial colonization.

Willingness to Respond in a Disaster: A Pediatric Nurse Practitioner National Survey

OBJECTIVE The objective of this study was to examine factors associated with pediatric nurse practitioners (PNPs) reporting to work in the event of a disaster. METHODS An anonymous national survey of PNPs was conducted. Several domains were explored, including demographics, personal preparedness plans, disaster training, prior disaster experience, and likelihood of responding in the event of a disaster. A logistic regression analysis was conducted to determine which factors were associated with the respondents likelihood of responding in the event of a disaster. RESULTS Factors associated with increased likelihood of responding included gender (being a male PNP), military experience, and disaster training. The most significant factor associated with an increased likelihood of responding to work during a disaster was having a specified role in the workplace disaster plan. PNPs with a specified role were three times more likely to respond than were those without a specified role. CONCLUSIONS PNPs are health care workers with advanced skill sets. This untapped resource is available to provide care for a vulnerable population: our children. Disaster planners should explore the possibility of utilizing these highly skilled health care workers in their disaster plans.

Induction of fibroblast growth factor 10 (FGF10) in the ileal crypt epithelium after massive small bowel resection suggests a role for FGF10 in gut adaptation.

We have previously reported that fibroblast growth factor 10 (FGF10) is crucial for the survival and proliferation of progenitor cells during embryonic gastrointestinal development. We sought to characterize the potential role of FGF10 signaling in the adaptive response following small bowel resection. Adult wild‐type and Fgf10LacZ mice underwent 50% small bowel resection (SBR) or sham operation. Tissues were harvested 24 or 48 hr after surgery for histology, immunohistochemistry, and in situ hybridization. After SBR, Fgf10 expression was demonstrated in the epithelium at the base of the crypts. Moreover, there was a statistically significant increase in proliferating cells and goblet cells after SBR. In vitro studies using rat intestinal epithelial crypt (IEC‐6) cells exposed to medium with or without recombinant FGF10 showed increased proliferation and phosphorylation of Raf and AKT with the addition of FGF10. Our results suggest that FGF10 may play a therapeutic role in diseases involving intestinal failure. Developmental Dynamics 238:294–301, 2009.