Effects of octreotide treatment on early TNF-alpha production and localization in experimental chronic colitis

Lanreotide Induces Cytokine Modulation in Intestinal Neuroendocrine Tumors and Overcomes Resistance to Everolimus

Somatostatin analogs mantain their major role in the treatment of patients with advanced neuroendocrine tumors (NETs) and have multiple modulatory effects on the immune system. Here, we evaluated the effects of lanreotide treatment on expression of Th1, Th2 cytokine patterns in serum of patients with NETs and in bronchial and pancreatic NET cell lines. Our results showed that lanreotide treatment promoted a Th1 cytotoxic immune-phenotype in patients with NETs originated by intestinal sites. Similar results were obtained also in vitro where lanreotide induced expression of Th1 cytokines only in pancreatic and not in bronchial-derived NET cell lines. It seems, therefore, that cytokinomics can represent a useful tool for the identification of tumor biomarkers for the early diagnosis and evaluation of the response to therapy in NET patients. To avoid the drug-resistance induced by everolimus (mTOR inhibitor), we made the pancreatic NET cell line resistant to this drug. After treatment with lanreotide we found that the drug reduced its viability compared to that of sensitive cells. These data may have direct implications in design of future translation combination trial on NET patients.

Neuropeptide receptors as potential drug targets in the treatment of inflammatory conditions

Cross-talk between the nervous, endocrine and immune systems exists via regulator molecules, such as neuropeptides, hormones and cytokines. A number of neuropeptides have been implicated in the genesis of inflammation, such as tachykinins and calcitonin gene-related peptide. Development of their receptor antagonists could be a promising approach to anti-inflammatory pharmacotherapy. Anti-inflammatory neuropeptides, such as vasoactive intestinal peptide, pituitary adenylate cyclase-activating polypeptide, α-melanocyte-stimulating hormone, urocortin, adrenomedullin, somatostatin, cortistatin, ghrelin, galanin and opioid peptides, are also released and act on their own receptors on the neurons as well as on different inflammatory and immune cells. The aim of the present review is to summarize the most prominent data of preclinical animal studies concerning the main pharmacological effects of ligands acting on the neuropeptide receptors. Promising therapeutic impacts of these compounds as potential candidates for the development of novel types of anti-inflammatory drugs are also discussed.

Effect of a somatostatin infusion on circulating levels of adipokines in obese women

OBJECTIVE

Changes in circulating levels of many adipocyte-derived peptides, including adipokines such as adiponectin, leptin and tumor necrosis factor alpha (TNF-α), have been reported in obesity (OB). Somatostatin (SRIF) inhibits circulating levels of adiponectin and leptin in lean (LN) subjects, but the effect of a SRIF infusion on these adipokines, including TNF-α, in OB is to date unknown.

METHODS

Ten young women (5 OB and 5 LN) were studied. All subjects underwent an infusion of SRIF (9 μg/kg/h i.v., over 60 min), with blood samples drawn prior to and at different time intervals after SRIF administration. Plasma levels of adiponectin, leptin and TNF-α were measured at each interval.

RESULTS

Basal levels of leptin and TNF-α were significantly higher in OB than LN women, whereas levels of adiponectin were significantly lower in OB than LN subjects. SRIF significantly inhibited plasma concentrations of adiponectin (at 60 min) in both OB and LN women, without affecting those of leptin and TNF-α in either group. In LN subjects, the inhibitory effect of SRIF on plasma adiponectin persisted up to 150 min, whereas SRIF infusion withdrawal in OB women resulted in a prompt restoration of basal levels of the adipokine.

CONCLUSIONS

Plasma concentrations of leptin and TNF-α, which are higher in OB than LN subjects, are unaffected by a SRIF infusion, which, in contrast, inhibits circulating levels of adiponectin in both groups, with a delayed return to the baseline secretion of the adipokine in LN subjects.

Infection with Hymenolepis diminuta is more effective than daily corticosteroids in blocking chemically induced colitis in mice

Purpose. To compare infection with the tapeworm, Hymenolepis diminuta, with steroid (dexamethasone) administration in the inhibition of dinitrobenzene sulfonic acid- (DNBS-) induced colitis in mice. Procedures. Mice were treated with DNBS ± infected with H. diminuta or treated with daily dexamethasone (2 mg/Kg, ip.) and were assessed 72 hours post-DNBS by the calculation of disease activity and histological damage scores, and spleen cell cytokine production. Results. H. diminuta-infected mice showed increased IL-4 and IL-10 production by spleen cells compared to other groups and were protected from DNBS-induced colitis. In contrast, there was little benefit of dexamethasone in the treatment of colitis. Collagen deposition in the colon was not different between the groups. Conclusions. H. diminuta was superior to dexamethasone in the prevention of DNBS-induced colitis and did not result in additional side effects (i.e., collagen deposition). Comparisons with current therapeutics and long-term followup to studies are essential if “helminth therapy” is to become a viable treatment for specific inflammatory diseases in the gut or other tissues.

Tumor necrosis factor-alpha impairs intestinal phosphate absorption in colitis

Phosphate homeostasis is critical for many physiological functions. Up to 85% of phosphate is stored in bone and teeth. The remaining 15% is distributed in cells. Phosphate absorption across the brush-border membrane (BBM) of enterocytes occurs mainly via a sodium-dependent pathway, which is mediated by type IIb sodium-phosphate cotransporters (NaPi-IIb). Patients of inflammatory bowel diseases (IBDs) suffer not only from diarrhea and nutrient malabsorption but also from bone loss. About 31-59% of patients with IBD develop bone disorders. Since the intestine is a primary location for dietary phosphate absorption, it is logical to postulate that there is an inverse relationship between gastrointestinal disorders and phosphate transport, which, in turn, contributes to bone disorders observed in patients with IBD. Phosphate absorption and NaPi-IIb expression was studied with BBM vesicles isolated from trinitrobenzene sulphonic acid (TNBS) animals as well as in Caco-2 cells. The mechanism of TNF-alpha downregulation of NaPi-IIb expression was investigated by luciferase assay, gel mobility shift assay (GMSA), and coimmunoprecipitation. Intestinal phosphate absorption mediated by NaPi-IIb was reduced both in TNBS colitis and in TNF-alpha-treated cells. Transient transfection indicated that TNF-alpha inhibits NaPi-IIb expression by reducing NaPi-IIb basal promoter activity. GMSAs identified NF1 protein as an important factor in TNF-alpha-mediated NaPi-IIb downregulation. Signaling transduction study and coimmunoprecipitation suggested that TNF-alpha interacts with EGF receptor to activate ERK1/2 pathway. Intestinal phosphate absorption mediated by NaPi-IIb protein is reduced in colitis. This inhibition is mediated by the proinflammatory cytokine TNF-alpha through a novel molecular mechanism involving TNF-alpha/EGF receptor interaction.

Protective effect of octreotide and infliximab in an experimental model of indomethacin-induced inflammatory bowel disease

Indomethacin administration in animals increases permeability of the small intestine, leading to inflammation that mimics Crohn's disease. Nonsteroidal anti-inflammatory drugs increase the permeability of the intestinal epithelial barrier and should therefore be used with caution in patients with Crohn's disease. We analyzed the protective effects of octreotide and the tumor necrosis factor-alpha inhibitor infliximab in a rat model of indomethacin-induced enterocolitis. Male Wistar rats received 20 mg of infliximab or 10 mug of octreotide 24 h prior to injection with indomethacin. Intestinal permeability was analyzed using Cr-51-ethylenediaminetetraacetic acid clearance. No microscopic or macroscopic alterations were observed in the rats receiving infliximab or octreotide, both of which increased permeability (P < 0.001 versus controls). Our macroscopic and microscopic findings might be related to the low specificity of infliximab and suggest that cytokines affect the intestinal epithelial barrier, as evidenced by the protective effect that infliximab had on the permeability parameters evaluated.

Octreotide regulates CC but not CXC LPS-induced chemokine secretion in rat Kupffer cells

Kupffer cells (KC) and lipopolysaccharide (LPS) interaction is the initial event leading to hepatic inflammation and fibrosis in many types of liver injury. We studied chemokine secretion by KC activated with LPS and the possible effect of the somatostatin analogue octreotide, in the regulation of this process. KC isolated from Sprague-Dawley rats were cultured in the presence of LPS added alone or with different concentrations of octreotide for 24 and 48 h, and chemokine production was assessed in culture supernatants by ELISA. CC chemokine mRNA expression was assessed by semiquantitative RT-PCR. Vehicle-stimulated KC produced a basal amount of CC and CXC chemokines. LPS-stimulated KC secreted significantly increased amounts of IL-8 (GRO/CINC-1) (P<0.001), MIP-2 (P<0.001), MCP-1 (P<0.001), and RANTES (P<0.01). Octreotide inhibited LPS-induced secretion of the CC chemokines MCP-1 (P<0.05) and RANTES (P<0.05), but not the CXC chemokines IL-8 (GRO/CINC-1) and MIP-2, in a concentration-dependent manner. Downregulation of basal and LPS-induced mRNA expression of the CC chemokines was also observed in the presence of octreotide. Pretreatment with phosphatidylinositol 3 (PI3)-kinase inhibitors reduced chemokine production by LPS-treated KC in both the mRNA and protein level. Furthermore, it prevented the octreotide inhibitory effect on LPS-induced chemokine secretion, indicating a possible involvement of the PI3-kinase pathway. In conclusion, these data demonstrate that chemokine secretion by KC can be differentially regulated by octreotide, and suggest that this somatostatin analogue may have immunoregulatory effects on resident liver macrophages. British Journal of Pharmacology (2004) 141, 477-487. doi:10.1038/sj.bjp.0705633

Octreotide reduces ischaemia-reperfusion injury in the retina

PURPOSE

To investigate the role of octreotide on retinal lipid peroxidation and histopathological changes during ischaemia/reperfusion (I/R).

METHODS

Three groups of seven pigmented guinea pigs each were formed. These represented a control group, an ischaemia group and an ischaemia/octreotide group. One eye of each animal was selected for histopathological evaluation and the other for biochemical assay. Bilateral pressure-induced retinal ischaemia was instigated for 90 min and was followed by 24 hours of reperfusion. Animals in the ischaemia/octreotide and ischaemia groups received either 10 micro g/kg of octreotide or saline, repeated five times at 6-hourly intervals, with the first dose administered 15 min prior to the ischaemic insult. Retinal malondialdehyde (MDA) levels and the thickness of the retinal layers were measured. These were compared with equivalent measurements of the control group.

RESULTS

The mean MDA level increased in the ischaemia group (p < 0.01) but not in the octreotide group (p > 0.05). Significant increases in the thickness of the overall retina (p < 0.01), inner retina (p < 0.05) ganglion cell layer (p < 0.01) inner plexiform layer (p < 0.01) and inner nuclear layer (p < 0.01) were observed in the ischaemia group. No significant difference in thickness was found in any of the layers in the ischaemia/octreotide group.

CONCLUSION

Octreotide reduces the increases in retinal MDA levels and retinal thickness observed during I/R.

Sequential expression of the neuropeptides substance P and somatostatin in granulomas associated with murine cysticercosis

Neurocysticercosis, a parasitic infection of the human central nervous system caused by Taenia solium, is a leading cause of seizures. Seizures associated with neurocysticercosis are caused mainly by the host inflammatory responses to dying parasites in the brain parenchyma. We previously demonstrated sequential expression of Th1 cytokines in early-stage granulomas, followed by expression of Th2 cytokines in later-stage granulomas in murine cysticercosis. However, the mechanism leading to this shift in cytokine response in the granulomas is unknown. Neuropeptides modulate cytokine responses and granuloma formation in murine schistosomiasis. Substance P (SP) induces Th1 cytokine expression and granuloma formation, whereas somatostatin inhibits the granulomatous response. We hypothesized that neuropeptides might play a role in regulation of the granulomatous response in cysticercosis. To test this hypothesis, we compared expression of SP and expression of somatostatin in murine cysticercal granulomas by using in situ hybridization and immunohistochemistry. We also compared expression with granuloma stage. Expression of SP mRNA was more frequent in the early-stage granulomas than in the late-stage granulomas (34 of 35 early-stage granulomas versus 1 of 13 late-stage granulomas). By contrast, somatostatin was expressed primarily in later-stage granulomas (13 of 14 late-stage granulomas versus 2 of 35 early-stage granulomas). The median light microscope grade of SP mRNA expression in the early-stage granulomas was significantly higher than that in the late-stage granulomas (P = 0.008, as determined by the Wilcoxon signed rank test). By contrast, somatostatin mRNA expression was higher at later stages (P = 0.008, as determined by the Wilcoxon signed rank test). SP and somatostatin are therefore temporally expressed in granulomas associated with murine cysticercosis, which may be related to differential expression of Th1 and Th2 cytokines.

Effects of tumour necrosis factor-alpha synthesis inhibitors on rat trinitrobenzene sulphonic acid-induced chronic colitis

The fact that tumour necrosis factor-alpha (TNF-alpha) is clearly involved in the pathogenesis of intestinal bowel disease, especially Crohn's disease, suggests that TNF-alpha synthesis inhibitors could be beneficial for treatment. The present study assessed the effect of chronic oral gavage of two in vitro TNF-alpha synthesis inhibitors, JM 34 maleate or [N-(4,6-dimethylpyridin-2-yl)-furane-2-carboxamide)] maleate and XC 21 or (N-betapicolyl-tetrafluorophtalimide), on colonic inflammation in trinitrobenzene sulphonic acid-induced colitis in rats. Rats received JM 34 maleate (100 mg/kg) and XC 21 (50 mg/kg) 1 h before colitis induction and then daily for 8 days by oral gavage. The colon was removed on day 8 and processed for clinical score, myeloperoxidase activity, and soluble TNF-alpha release. Treatment with XC 21, as well as dexamethasone and sulphasalazine, reduced colonic damage and decreased (except with dexamethasone) the incidence of diarrhoea. JM 34 maleate failed to improve the clinical signs of chronic colitis. After trinitrobenzene sulphonic acid-induced colitis, myeloperoxidase activity and TNF-alpha colonic mucosal production were substantially increased compared to the control (saline instillation). Both of these inflammatory indicators were then significantly decreased (P< or =0.05) after the four chronic treatments (JM 34 maleate, XC 21, sulphasalazine, and dexamethasone). XC 21 appeared to be as efficient as sulphasalazine in improving colonic inflammation.