Lipopolysaccharide Increases Plasma Levels of Corticotropin-Releasing Hormone in Rats

Abstract

Background: Corticotropin-releasing hormone (CRH) is expressed in the brain, immune cells and the gut, where gene expression is upregulated by lipopolysaccharide (LPS) 6 h after injection. Whether these changes are reflected by increased circulating levels of CRH and adrenocorticotropic hormone (ACTH) is unknown. Methods: LPS (100 µg/kg) was injected intraperitoneally in conscious rats, and blood processed for CRH using the new RAPID (reduced temperatures, acidification, protease inhibition, isotopic exogenous controls and dilution) method compared with EDTA blood with or without plasma methanol extraction. Hormone levels were measured by commercial radioimmunoassay. Results: The RAPID method improved blood recovery of ¹²⁵I-CRH in vitro compared to EDTA only added to the blood without or with methanol extraction (90.8 ± 2.0 vs. 66.9 ± 2.6 and 47.5 ± 2.0%, respectively; p < 0.001 vs. RAPID). Basal CRH levels from blood processed by the RAPID method were 28.9 ± 2.8 pg/ml, and by other methods below the radioimmunoassay detection limit (<10 pg/ml). At 6 h after LPS, CRH plasma levels increased significantly by 2.9 times, and in the proximal colon tended to decrease (–27.6 ± 5.7%; p > 0.05), while circulating levels were unchanged at 3 or 4 h. ACTH levels rose compared to control rats (135.3 ± 13.8 vs. 101.4 ± 6.0 pg/ml; p < 0.05) 30 min after the increase in CRH, while at 3 or 6 h after LPS, the levels were not changed. Conclusion: Intraperitoneal LPS induces a delayed rise in plasma CRH levels associated with an elevation in ACTH plasma levels 30 min later, suggesting that under conditions of immune challenge, CRH of peripheral origin may also contribute to pituitary activation, as detected using the RAPID method of blood processing, which improves CRH recovery.

Urocortins and CRF type 2 receptor isoforms expression in the rat stomach are regulated by endotoxin: role in the modulation of delayed gastric emptying

“…These data are consistent with previous reports showing a long-lasting reduction of gastric transit of liquid or solid induced by peripheral injection of LPS at similar or lower doses in rats (6,19,64). Under these conditions, peripheral injection of the long-lasting CRF 2 receptor antagonist astressin 2 -B (52) further enhanced the inhibitory effect of LPS by 31%.…”

“…Next, we delineated the expression of Ucns and CRF 2b in multiple defined layers of the GC, including myenteric neurons, using the laser capture microdissection (LCM) system combined with reverse transcription polymerase chain reaction (RT-PCR). The regulation of Ucns/CRF 2b gene expression in the gastric mucosa and SϩM over a 24-h period was assessed following LPS injected intraperitoneally at a single dose of 100 g/kg previously established to reduce gastric emptying (4,19,64), mimicking some of the clinical features of acute Gramnegative bacterial infection without apparent signs of severe sickness found in endotoxin shock induced by milligram doses of LPS (38). Previously, we identified in the rat esophagus and lower esophagus sphincter (LES) the novel CRF 2 splice variant CRF 2a and the other related isoform CRF 2a-3 , which contains the entire intron 3 (67).…”

Regulation of NUCB2/nesfatin-1 production in rat's stomach and adipose tissue is dependent on age, testosterone levels and lactating status

“…2A). Accordingly to previous data in the bibliography by using the same antibody, NUCB2 detection in gastric mucosa by western blot image showed a double band at 50 kDa (Goebel et al, 2011;Li et al, 2012;Riva et al, 2011;Stengel et al, 2009). Measurements of the gastric NUCB2/nesfatin-1 expression showed that the mRNA levels of NUCB2 were significantly higher just after the weaning, i.e., at 4 weeks of age (1.00 ± 0.05 at 2 weeks, 1.41 ± 0.10 at 4 weeks vs 1.29 ± 0.13 at 6 weeks and 1.14 ± 0.09 at 8 weeks arbitrary units; *p ≤ 0.05 vs 2-weeks-old) (Fig.…”

Orexigenic response to tail pinch: role of brain NPY1 and corticotropin releasing factor receptors

“…The underlying mechanisms of acute stress-related reduction of food intake are largely linked to the activation of corticotropin releasing factor (CRF) signaling pathways. It is well documented that various stressors including wrap restraint stress, low dose of lipopolysaccharide, or abdominal surgery activate the hypothalamic/CRF-pituitary-adrenal axis as shown by Fos or Fos/CRF colabeling in stress-responsive hypothalamic regions and the related elevation of circulating adrenocorticotropic hormone (ACTH) and corticosterone (8,19). Moreover, CRF and the related peptides urocortin 1 or urocortin 2 injected centrally or peripherally reduce feeding via activation of brain CRF receptor subtypes 1 (CRF 1 ) and 2 (CRF 2 ) and peripheral CRF 2 receptor in rats (48,67,71).…”