Therapeutic effect of exogenous ghrelin in the healing of gingival ulcers is mediated by the release of endogenous growth hormone and insulin-like growth factor-1

Ghrelin, an acylated 28-amino acid polypeptide, was primary isolated from the stomach, and the stomach is a main source of circulating ghrelin. Ghrelin strongly and dose-dependently stimulates release of growth hormone from the anterior pituitary, as well as increases food intake and fat deposition. Previous studies showed that ghrelin exhibits protective and therapeutic effect in different parts of the gastrointestinal system, including the oral cavity. The aim of present study was to examine the role of growth hormone and insulin-like growth factor-1 (IGF-1) in the healing of gingival ulcers. Studies were performed on rats with the intact pituitary gland and hypophysectomized rats. In anesthetized rats, chronic ulcers of the gum were induced by acetic acid. Rats were treated intraperitoneally twice a day with saline or ghrelin (4, 8 or 16 nmol/kg/dose) for six days. In pituitary-intact rats, administration of ghrelin significantly increased serum concentration of growth hormone and IGF-1 and this effect was associated with a significant increase in the healing rate of gingival ulcers. Moreover, treatment with ghrelin increased mucosal blood flow and DNA synthesis in the gum, while a local inflammation was decreased what was observed as a reduction in mucosal concentration of pro-inflammatory interleukin-1β. Hypophysectomy decreased serum level of growth hormone below a detection limit; whereas serum concentration of IGF-1 was reduced by 90%. On the other hand, removal of the pituitary gland was without any significant effect on the healing rate of gingival ulcers or on the ulcer-induced increase in DNA synthesis and concentration of pro-inflammatory interleukin-1β in gingival mucosa. Administration of ghrelin failed to affect serum level of growth hormone and IGF-1 in hypophysectomized rats, and was without any effect on the healing rate of gingival ulcers, mucosal blood flow, DNA synthesis or concentration of interleukin-1β in gingival mucosa. Neither induction of gingival ulcers nor hypophysectomy nor administration of ghrelin significantly affected serum concentration of pro-inflammatory interleukin-1β. We concluded that endogenous growth hormone and IGF-1 were involved in the therapeutic effect of exogenous ghrelin in the healing of gingival mucosa damage.

Pretreatment with low doses of acenocoumarol inhibits the development of acute ischemia/reperfusion-induced pancreatitis

Coagulative disorders are known to occur in acute pancreatitis and are related to the severity of this disease. Various experimental and clinical studies have shown protective and therapeutic effect of heparin in acute pancreatitis. Aim of the present study was to determine the influence of acenocoumarol, a vitamin K antagonist, on the development of acute pancreatitis. Studies were performed on male Wistar rats weighing 250 - 270 g. Acenocoumarol at the dose of 50, 100 or 150 μg/kg/dose or vehicle were administered once a day for 7 days before induction of acute pancreatitis. Acute pancreatitis was induced in rats by pancreatic ischemia followed by reperfusion. The severity of acute pancreatitis was assessed after 5-h reperfusion. Pretreatment with acenocoumarol given at the dose of 50 or 100 μg/kg/dose reduced morphological signs of acute pancreatitis. These effects were accompanied with a decrease in the pancreatitis-evoked increase in serum activity of lipase and serum concentration of pro-inflammatory interleukin-1β. Moreover, the pancreatitis-evoked reductions in pancreatic DNA synthesis and pancreatic blood flow were partially reversed by pretreatment with acenocoumarol given at the dose of 50 and 100 μg/kg/dose. Administration of acenocoumarol at the dose of 150 μg/kg/dose did not exhibit any protective effect against ischemia/reperfusion-induced pancreatitis. We concluded that pretreatment with low doses of acenocoumarol reduces the severity of ischemia/reperfusion-induced acute pancreatitis.

Involvement of cyclooxygenase-1 and cyclooxygenase-2 activity in the therapeutic effect of ghrelin in the course of ethanol-induced gastric ulcers in rats

Previous studies have shown that treatment with ghrelin exhibits protective and therapeutic effects in the gut. Aim of our present investigation was to examine the influence of ghrelin administration on the healing of ethanol-induced gastric ulcers and determine the role of cyclooxygenase-1 and cyclooxygenase-2 in this effect. Our studies were performed on male Wistar rats. Gastric ulcers were induced by intragastric administration of 75% ethanol. Ghrelin alone or in combination with cyclooxygenase inhibitors was administered twice, 1 and 13 hours after ethanol application. Cyclooxygenase-1 (COX-1) inhibitor (SC-560, 10 mg/kg/dose) or COX-2 inhibitor (celecoxib, 10 mg/kg/dose) were given 30 min prior to ghrelin. Twelve or 24 hours after administration of ethanol, rats were anesthetized and experiments were terminated. The study revealed that administration of ethanol induced gastric ulcers in all animals and this effect was accompanied by the reduction in gastric blood flow and mucosal DNA synthesis. Moreover induction of gastric ulcer by ethanol significantly increased mucosal expression of mRNA for COX-2, IL-1β and TNF-α. Treatment with ghrelin significantly accelerated gastric ulcer healing. Therapeutic effect of ghrelin was associated with significant reversion of the ulcer-evoked decrease in mucosal blood flow and DNA synthesis. Ghrelin administration also caused the reduction in mucosal expression of mRNA for IL-1β and TNF-α. Addition of SC-560 slightly reduced the therapeutic effect of ghrelin in the healing of ethanol-induced ulcer and the ulcer area in rats treated SC-560 plus ghrelin was significantly smaller than that observed in rats treated with saline or SC-560 alone. Pretreatment with celecoxib, a COX-2 inhibitor, abolished therapeutic effect of ghrelin. We concluded that treatment with ghrelin increases healing rate of gastric ulcers evoked by ethanol and this effect is related to improvement in mucosal blood flow, an increase in mucosal cell proliferation, and reduction in mucosal expression of proinflammatory cytokines. Ghrelin is able to reverse a deleterious effect of COX-1 inhibitor on healing of ethanol-induced gastric ulcers. Activity of COX-2 is necessary for the therapeutic effect of ghrelin in healing of ethanol-induced gastric ulcers.

Ghrelin accelerates the healing of oral ulcers in non-sialoadenectomized and sialoadenectomized rats

Ghrelin exhibits protective and therapeutic effect in different parts of the gastrointestinal tract. The aim of the present study was to examine the influence of ghrelin administration on the healing of oral ulcers in rats with intact salivary gland and in sialoadenectomized rats. Gingival and lingual ulcers were induced by acetic acid. After induction of ulcers, rats were treated with saline or ghrelin for six days. In rats with intact salivary glands and induction of oral ulcers, administration of ghrelin significantly increased the healing rate of these ulcers. This result was associated with a significant increase in mucosal blood flow and cell proliferation, and a decrease in concentration of pro-inflammatory interleukin-1β in gingival and lingual mucosa. Sialoadenectomy decreased cell proliferation and increased concentration of pro-inflammatory interleukin-1β in oral mucosa, as well as reduced the healing rate of gingival and lingual ulcers. Administration of ghrelin reversed deleterious effect of sialoadenectomy and increased the healing rate of oral ulcers above a value observed in rats with intact salivary glands.

CONCLUSIONS

Treatment with ghrelin accelerates healing of oral ulcers in salivary glands-intact rat, as well as in rats with reduced salivary secretion evoked by sialoadenectomy. Mechanisms of beneficial effects of ghrelin administration involve an increase in mucosal blood flow and cell proliferation, as well as a reduction in local inflammation.

Heparin inhibits protective effect of ischemic preconditioning in ischemia/reperfusion-induced acute pancreatitis

Previous studies have shown that pancreatic ischemic preconditioning or heparin, applied before induction of acute pancreatitis inhibit the development of this disease and accelerate pancreatic recovery. The aim of the study was to determine the influence of treatment with heparin on protective effect of ischemic preconditioning (IP) in ischemia/reperfusion-induced acute pancreatitis. Heparin was administered twice, before and during induction of acute pancreatitis. IP was performed by short-term clamping of celiac artery, 30 min before induction of acute pancreatitis. Acute pancreatitis was induced in rats by clamping of inferior splenic artery for 30 min followed by reperfusion. Rats were sacrificed after 6-h and 24-h reperfusion.

RESULTS

IP applied alone caused a mild pancreatic damage associated with a limited increase in plasma amylase activity, concentration of pro-inflammatory interleukin-1β and plasma level of D-dimer. Pretreatment with heparin or IP applied alone reduced the severity of acute pancreatitis. Both these procedures caused a similar reduction in plasma lipase, amylase and interleukin-1β, as well as in histological signs of pancreatic damage. These changes were associated with partial reversion of the pancreatitis-evoked fall of pancreatic blood flow and DNA synthesis. Combination of heparin plus IP reduced the protective effect of heparin or IP applied alone. It was manifested by an increase in pancreatic damage and plasma level of lipase, amylase and interleukin-1β, as well as by reduction in pancreatic DNA synthesis and plasma concentration of D-dimer and interleukin-10.

CONCLUSIONS

heparin abolishes the protective effect of ischemic preconditioning in ischemia reperfusion-induced pancreatitis. This observation suggests that initial clot formation is necessary to induce pancreatic protection by IP.

Role of sensory nerves in gastroprotective effect of anandamide in rats

Previous studies have shown that stimulation of cannabinoid 1 (CB1) receptor protects the gastric mucosa against stress-induced lesion. Aim of the present study was to examine the influence of anandamide on lipid peroxidation and antioxidant defense system in gastric mucosa and the role of sensory nerves in gastroprotective effects of cannabinoids. Studies were performed on rats with intact or ablated sensory nerves (by neurotoxic doses of capsaicin). Gastric lesions were induced by water immersion and restrain stress (WRS). Anandamide was administered at the dose of 0.3, 1.5 or 3.0 μmol/kg, 30 min before exposure to WRS. CB1 receptor antagonist, AM251 (4.0 μmol/kg) was administered 40 min before WRS. WRS induced gastric lesions associated with the decrease in gastric blood flow, mucosal DNA synthesis and mucosal activity of superoxide dismutase (SOD). Serum level of interleukin-1β (IL-1β) and mucosal level of malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE) were increased. Administration of anandamide reduced the ulcers area, generation of MDA+4-HNE and serum level of IL-1β, and this effect was associated with the reduction in the WRS-induced decrease in gastric mucosal blood flow, mucosal DNA synthesis and SOD activity. Ablation of sensory nerves increased the area of ulcers, serum level of IL-1β and mucosal content of MDA+4-HNE, whereas mucosal DNA synthesis, SOD activity and blood flow were additionally decreased. In rats with ablation of sensory nerves, administration of anandamide at the high doses (1.5 and 3.0 μmol/kg) partly reduced deleterious effect of WRS on gastric mucosa, but this effect was weaker than in animals with intact sensory nerves. Low dose of anandamide (0.3 μmol/kg) was ineffective in the protection of gastric mucosa against the WRS-induced lesions in rats with ablation of sensory nerves. In rats with intact sensory nerves and exposed to WRS, administration of AM251 exhibited deleterious effect. In rats with ablation of sensory nerves and exposed to WRS, AM251 failed to affect mucosal injury in the stomach. We conclude that anandamide reduces the mucosal oxidative stress and exhibits gastroprotective effect against WRS-induced ulcers. These effects are partly mediated by sensory nerves.

Pretreatment with obestatin inhibits the development of cerulein-induced pancreatitis

Obestatin is a peptide derived from the proghrelin, a common prohormone for ghrelin and obestatin. Obestatin, like the ghrelin has been originally extracted from rat stomach, and the stomach seems to be a major source of circulating obestatin. Previous studies have shown that administration of ghrelin exhibits protective effect in the pancreas, inhibiting the development of acute pancreatitis. Recent study has shown that obestatin promotes survival of beta-cells and pancreatic islets. Aim of the present study was to investigate the influence of obestatin administration on the development of cerulein-induced pancreatitis. Studies were performed on male Wistar rats. Acute pancreatitis was induced by cerulein given intraperitoneally 5 times at a dose of 50 microg/kg/dose with 1-h intervals. Obestatin was injected twice intraperitoneally at the dose of 4, 8 or 16 nmol/kg/dose. In control saline-treated rats, obestatin was without effect on pancreatic morphology, serum activity of pancreatic enzymes, serum level of pro-inflammatory interleukin-1beta or pancreatic cells proliferation. In animals with induction of acute pancreatitis, morphological examination showed that administration of obestatin decreased pancreatic leukocyte infiltration and vacuolization of acinar cells. These effects were accompanied by reduction in the pancreatitis-evoked increase in serum level of pancreatic digestive enzymes, lipase amylase and poly-C ribonuclease. Obestatin administered at the highest dose of 16 nmo/kg/dose reduced serum activity of these enzymes by 33, 42 and 44%, respectively. Also serum concentration of pro-inflammatory interleukin-1beta was decreased by obestatin in rats with acute pancreatitis; whereas the pancreatitis-evoked decrease in pancreatic blood flow and pancreatic DNA synthesis was partially reversed. Administration of obestatin reduces the severity of cerulein-induced acute pancreatitis. This effect is related, at least in part, to the improvement of pancreatic blood flow and reduction in proinflammatory interleukin-1beta release.

Protective and therapeutic effect of heparin in acute pancreatitis

The initiation and progression of acute pancreatitis is associated with disturbances in pancreatic microcirculatory. Microcirculatory disorders contribute to multiorgan dysfunction syndrome in the course of acute pancreatitis. The aim of this study was to determine the influence of heparin administration on the development and the course of ischemia/reperfusion-induced pancreatitis.

METHODS

Acute pancreatitis was induced in rats by pancreatic ischemia followed by reperfusion. In the first series of studies, heparin was administered 0.5 h before induction of acute pancreatitis and the severity of acute pancreatitis was assessed after 6-h reperfusion. In the second series of studies, heparin was administered twice a day, starting 24 h after the initiation of reperfusion. In both series of studies, heparin was administered subcutaneously at the dose of 150 U/kg.

RESULTS

Treatment with heparin, before induction of pancreatitis, inhibits the development of morphological signs of acute pancreatitis and reduced the pancreatitis-evoked increase in plasma level of pancreatic enzymes and pro-inflammatory interleukin-1beta. These effects have been accompanied with improvement of pancreatic blood flow, pancreatic DNA synthesis and reduction in plasma concentration of D-dimer. Administration of heparin after induction of acute pancreatitis accelerates normalization of pancreatic histology, and reduces biochemical markers of the severity of acute pancreatitis. These effects have been accompanied with the improvement of pancreatic circulation, increase in APTT and reduction in plasma D-dimer level.

CONCLUSIONS

Treatment with heparin inhibits the development of ischemia/reperfusion-induced pancreatitis and accelerates pancreatic regeneration in the course of this disease.

Microglia-derived TGF-β as an important regulator of glioblastoma invasion—an inhibition of TGF-β-dependent effects by shRNA against human TGF-β type II receptor

The invasion of tumor cells into brain tissue is a pathologic hallmark of malignant gliomas and contributes to treatment failures. Diffuse glioblastomas contain numerous microglial cells, which enhance the progression of gliomas; however, factors responsible for invasion-promoting role of microglia are unknown. Transforming growth factor-beta (TGF-beta) can enhance tumor growth, invasion, angiogenesis and immunosuppression. Antagonizing TGF-beta activity has been shown to inhibit tumor invasion in vitro and tumorigenicity, but a systemic inhibition or lack of TGF-beta signaling results in acute inflammation and disruption of immune system homeostasis. We developed plasmid-transcribed small hairpin RNAs (shRNAs) to downregulate the TGF-beta type II receptor (TbetaIIR) expression, which effectively inhibited cytokine-induced signaling pathways and transcriptional responses in transiently transfected human glioblastoma cells. Silencing of TbetaIIR abolished TGF-beta-induced glioblastoma invasiveness and migratory responses in vitro. Moreover, tumorigenicity of glioblastoma cells stably expressing TbetaIIR shRNAs in nude mice was reduced by 50%. Microglia strongly enhanced glioma invasiveness in the co-culture system, but this invasion-promoting activity was lost in glioma cells stably expressing shTbetaRII, indicating a crucial role of microglia-derived TGF-beta in tumor-host interactions. Our results demonstrate a successful targeting of TGF-beta-dependent invasiveness and tumorigenicity of glioblastoma cells by RNAi-mediated gene silencing.

Extract of grapefruit-seed reduces acute pancreatitis induced by ischemia/reperfusion in rats: possible implication of tissue antioxidants

Grapefruit seed extract (GSE) has been shown to exert antibacterial, antifungal and antioxidant activity possibly due to the presence of naringenin, the flavonoid with cytoprotective action on the gastric mucosa. No study so far has been undertaken to determine whether this GSE is also capable of preventing acute pancreatic damage induced by ischemia/reperfusion (I/R), which is known to result from reduction of anti-oxidative capability of pancreatic tissue, and whether its possible preventive effect involves an antioxidative action of this biocomponent. In this study carried out on rats with acute hemorrhagic pancreatitis induced by 30 min partial pancreatic ischemia followed by 6 h of reperfusion, the GSE or vehicle (vegetable glycerin) was applied intragastrically in gradually increasing amounts (50-500 microl) 30 min before I/R. Pretreatment with GSE decreased the extent of pancreatitis with maximal protective effect of GSE at the dose 250 microl. GSE reduced the pancreatitis-evoked increase in serum lipase and poly-C specific ribonuclease activity, and attenuated the marked fall in pancreatic blood flow and pancreatic DNA synthesis. GSE administered alone increased significantly pancreatic tissue content of lipid peroxidation products, malondialdehyde and 4-hydroxyalkens, and when administered before I/R, GSE reduced the pancreatitis-induced lipid peroxidation. We conclude that GSE exerts protective activity against I/R-induced pancreatitis probably due to the activation of antioxidative mechanisms in the pancreas and the improvement of pancreatic blood flow.

Refractive Q-switching of a ruby laser by a moving plasma

A ruby laser was Q-switched by means of a plasma. The plasma, which had a density of up to 10(18) cm(-3), was produced in an electromagnetic shock tube. The density gradient created by the reflected plasma was large enough to produce measurable refraction of the laser beam. The laser cavity, which was initially misaligned, attained perfect alignment when the plasma was introduced into the cavity.