Fasting-induced intestinal apoptosis is mediated by inducible nitric oxide synthase and interferon-γ in rat

Abstract

Ito J, Uchida H, Yokote T, Ohtake K, Kobayashi J. Fastinginduced intestinal apoptosis is mediated by inducible nitric oxide synthase and interferon-␥ in rat. Am J Physiol Gastrointest Liver Physiol 298: G916 -G926, 2010. First published April 8, 2010 doi:10.1152/ajpgi.00429.2009 is associated with intestinal apoptosis in health and disease. This study aimed to investigate the role of intestinal NO in the regulation of apoptosis during fasting in rats. Male Wistar rats were divided into two groups and subcutaneously injected with saline (SA) or aminoguanidine (AG), followed by fasting for 24, 48, 60, and 72 h. At each time point, the jejunum was subjected to histological evaluation for enterocyte apoptosis by histomorphometric assessment and TUNEL analysis. We performed immunohistochemistry for inducible NO synthase (iNOS) expression in the jejunum and measured tissue nitrite levels using HPLC and 8-hydroxydeoxyguanosine adduct using ELISA, indicative of endogenous NO production and reactive oxygen species (ROS) production, respectively. Jejunal transcriptional levels of iNOS, neuronal NO synthase (nNOS), and interferon-␥ (IFN-␥) were also determined by RT-PCR. Fasting caused significant jejunal mucosal atrophy due to attenuated cell proliferation and enhanced apoptosis with increase in iNOS transcription, its protein expression in intestinal epithelial cells (IEC), and jejunal nitrite levels. However, AG treatment histologically reduced apoptosis with inhibition of fastinginduced iNOS transcription, protein expression, and nitrite production. We also observed fasting-induced ROS production and subsequent IFN-␥ transcription, which were all inhibited by AG treatment. Furthermore, we observed reduced transcriptional levels of nNOS, known to suppress iNOS activation physiologically. These results suggest that fasting-induced iNOS activation in IEC may induce apoptosis mediators such as IFN-␥ via a ROS-mediated mechanism and also a possible role of nNOS in the regulation of iNOS activity in fasting-induced apoptosis.aminoguanidine; reactive oxygen species; intestinal epithelial cells; neuronal nitric oxide synthase THE GASTROINTESTINAL EPITHELIUM is a dynamic tissue characterized by a high cellular turnover rate with a balance between cell proliferation and cell apoptosis, consequently leading to renewal of the entire intestinal epithelium every 3-5 days (9,19). This single layer of cells lining the gut lumen acts as a barrier against harmful intraluminal entities, including foreign antigens, microorganisms, and toxins, and also acts as a selective filter allowing the translocation of essential dietary nutrients, electrolytes, and water. However, these physiological functions are occasionally impaired under pathological conditions such as inflammation and ischemia-reperfusion and are accompanied by intestinal histological changes, including apoptosis.Fasting is likely a physiological challenge evoking a response to the absence of luminal nutrients by functional and morphological changes, including intestinal epithe...

Effects of fasting and refeeding on intestinal cell proliferation and apoptosis in hammerhead shark (Sphyrna lewini)

“…In the advanced tubular intestine of tetrapods (e.g., mammals, chicken and reptiles) [20][21][22][23][24][25][26] , similar localizations of apoptotic or proliferating cells in the epithelia have been reported, whereas proliferating cells in fresh water and apoptotic cells in seawater were observed throughout the intestinal epithelia of euryhaline teleosts [15,27] . Furthermore, the degree of cell proliferation and apoptosis were modified in both intestinal epithelia of the shark and the murines by fasting/feeding, but in opposite directions [5,6,28,29] . Whereas a reversible decrease in the epithelial apoptosis and cell proliferation are observed in the shark during fasting, epithelial cell turnover is induced in the murine intestinal mucosa after fasting [6,28,29] .…”

“…Furthermore, the degree of cell proliferation and apoptosis were modified in both intestinal epithelia of the shark and the murines by fasting/feeding, but in opposite directions [5,6,28,29] . Whereas a reversible decrease in the epithelial apoptosis and cell proliferation are observed in the shark during fasting, epithelial cell turnover is induced in the murine intestinal mucosa after fasting [6,28,29] . This difference may reflect the differing feeding ecology of sharks most of which, unlike murines, tend to eat large meals at irregular intervals [30,31] .…”

Inducible and neuronal nitric oxide synthases exert contrasting effects during rat intestinal recovery following fasting

“…To measure enterocyte apoptosis in the jejunum, the apoptotic index (AI) was calculated by conventional light microscopy of H&E-stained specimens, following the methods of Dahly et al and Ito et al 6,9 Terminal deoxynucleotidyl transferase dUTP nick-end labelling (TUNEL) staining of apoptotic cells is easy to interpret for all images; however, because of its nonspecific staining, representative apoptotic changes were utilized for the analysis of AI. In brief, jejunal sections as used above for histopathological analysis were examined in a blinded manner for the typical attributes of apoptotic cells.…”

“…For instance, rat small intestines with histological abnormalities demonstrate increased iNOS expression. 9,12 nNOS is the predominant isoform in the intestine, and its activity is inversely correlated with the extent of tissue injury. 13 Previous investigations using animal models have suggested that nNOS and iNOS are key in the development and progression of post-inflammatory functional gastrointestinal disorders, 14 ischemia-reperfusion injury (IRI), acute rejection (AR) in intestinal transplantation, 15 and necrotizing enterocolitis (NEC).…”

Nutrient-intake-level-dependent regulation of intestinal development in newborn intrauterine growth-restricted piglets via glucagon-like peptide-2

“…It is known that the homeostasis of the intestinal apoptotic system is sensitive to enteral nutrient intake . Thus, the apoptotic process can be quickly initiated if enteral nutrient intake is insufficient, which can in turn lead to intestinal atrophy (Niinikoski et al, 2004;Ito et al, 2010;Dodge et al, 2012). However, it remains unclear whether such nutrientintake-level-dependent regulation of the development of the small intestine exists in IUGR neonates.…”