Pharmacological targeting of protease-activated receptor 2 affords protection from bleomycin-induced pulmonary fibrosis

Idiopathic pulmonary fibrosis is the most devastating diffuse fibrosing lung disease that remains refractory to therapy. Despite increasing evidence that protease-activated receptor 2 (PAR-2) contributes to fibrosis, its importance in pulmonary fibrosis is under debate. We addressed whether PAR-2 deficiency persistently reduces bleomycin-induced pulmonary fibrosis or merely delays disease progression and whether pharmacological PAR-2 inhibition limits experimental pulmonary fibrosis. Bleomycin was instilled intranasally into wild-type or PAR-2-deficient mice in the presence/absence of a specific PAR-2 antagonist (P2pal-18S). Pulmonary fibrosis was consistently reduced in PAR-2-deficient mice throughout the fibrotic phase, as evident from reduced Ashcroft scores (29%) and hydroxyproline levels (26%) at d 28. Moreover, P2pal-18S inhibited PAR-2-induced profibrotic responses in both murine and primary human pulmonary fibroblasts (p < 0.05). Once daily treatment with P2pal-18S reduced the severity and extent of fibrotic lesions in lungs of bleomycin-treated wild-type mice but did not further reduce fibrosis in PAR-2-deficient mice. Importantly, P2pal-18S treatment starting even 7 d after the onset of fibrosis limits pulmonary fibrosis as effectively as when treatment was started together with bleomycin instillation. Overall, PAR-2 contributes to the progression of pulmonary fibrosis, and targeting PAR-2 may be a promising therapeutic strategy for treating pulmonary fibrosis

Memantine, a noncompetitive NMDA receptor antagonist improves hyperammonemia-induced encephalopathy and acute hepatic encephalopathy in rats

The aim of this study was to investigate the possible role of N-methyl-D-aspartate (NMDA)-receptor overactivity in two different experimental rat models of encephalopathy: subacute encephalopathy caused by severe hyperammonemia in portacaval-shunted rats (AI-PCS rats) and acute hepatic encephalopathy caused by complete liver ischemia (LIS rats). The effect of the noncompetitive NMDA-receptor antagonist memantine (intraperitoneal [i.p.] 10-20 mg/kg bw or intravenous [i.v.] 5 mg/kg bw) was studied on the severity of encephalopathy by assessment of clinical grading and electroencephalogram (EEG) spectral analysis, on plasma ammonia concentrations, amino acid concentrations in cerebrospinal fluid (CSF), intracranial pressure (ICP), and brain water content. Both rat models developed encephalopathy within 3 to 6 hours, associated with increased CSF glutamate and aspartate concentrations and increased ICP and brain water content. Memantine administration in AI-PCS and LIS rats resulted in a significant improvement in clinical grading and less slowing of EEG activity (P <.05), and smaller increases in CSF glutamate (P <.05) concentrations. Moreover, ICP and brain water content were significantly lower in memantine-treated AI-PCS rats than in untreated AI-PCS rats (P <.05). Memantine had no significant effect on ICP and brain water content in LIS rats, and on ammonia concentrations in both models. These results indicate that NMDA-receptor activation might be involved in the pathogenesis of hyperammonemia-induced encephalopathy and of acute hepatic encephalopathy caused by LI

Dabigatran Potentiates Gemcitabine-Induced Growth Inhibition of Pancreatic Cancer in Mice

Pancreatic cancer is one of the most lethal solid malignancies, with few treatment options. We have recently shown that expression of protease activated receptor (PAR)- 1 in the tumor microenvironment drives the progression and induces the chemoresistance of pancreatic cancer. As thrombin is the prototypical PAR-1 agonist, here we address the effects of the direct thrombin inhibitor dabigatran on pancreatic cancer growth and drug resistance in an orthotropic pancreatic cancer model. We show that dabigatran treatment did not affect primary tumor growth, whereas it significantly increased tumor dissemination throughout the peritoneal cavity. Increased dissemination was accompanied by intratumoral bleeding and increased numbers of aberrant and/or collapsed blood vessels in the primary tumors. In combination with gemcitabine, dabigatran treatment limited primary tumor growth, did not induce bleeding complications and prevented tumor cell dissemination. Dabigatran was, however, not as efficient as genetic ablation of PAR-1 in our previous study, suggesting that thrombin is not the main PAR-1 agonist in the setting of pancreatic cancer. Overall, we show that dabigatran potentiates gemcitabine-induced growth inhibition of pancreatic cancer but does not affect primary tumor growth when used as monotherap

Dabigatran Potentiates Gemcitabine-Induced Growth Inhibition of Pancreatic Cancer in Mice

Pancreatic cancer is one of the most lethal solid malignancies, with few treatment options. We have recently shown that expression of protease activated receptor (PAR)- 1 in the tumor microenvironment drives the progression and induces the chemoresistance of pancreatic cancer. As thrombin is the prototypical PAR-1 agonist, here we address the effects of the direct thrombin inhibitor dabigatran on pancreatic cancer growth and drug resistance in an orthotropic pancreatic cancer model. We show that dabigatran treatment did not affect primary tumor growth, whereas it significantly increased tumor dissemination throughout the peritoneal cavity. Increased dissemination was accompanied by intratumoral bleeding and increased numbers of aberrant and/or collapsed blood vessels in the primary tumors. In combination with gemcitabine, dabigatran treatment limited primary tumor growth, did not induce bleeding complications and prevented tumor cell dissemination. Dabigatran was, however, not as efficient as genetic ablation of PAR-1 in our previous study, suggesting that thrombin is not the main PAR-1 agonist in the setting of pancreatic cancer. Overall, we show that dabigatran potentiates gemcitabine-induced growth inhibition of pancreatic cancer but does not affect primary tumor growth when used as monotherap

Therapy-resistant tumor microvascular endothelial cells contribute to treatment failure in glioblastoma multiforme

Glioblastoma multiforme (GBM) is a devastating disease with high mortality and poor prognosis. Cancer stem cells (CSCs) have recently been defined as a fraction of tumor cells highly resistant to therapy and subsequently considered to be responsible for tumor recurrence. These cells have been characterized in GBM and suggested to reside in and be supported by the tumor microvascular niche. Here we evaluated the response of tumor microvascular endothelial cells (tMVECs) to radio- and chemotherapy, and analyzed how this affects their interaction with CSCs. Our data demonstrate that tMVECs exhibit extreme resistance to both therapies, with the main response to irradiation being senescence. Importantly, senescent tMVECs can be detected in human GBM samples as well as in mice upon irradiation. Even though permanently arrested, they are still viable and able to support CSC growth with the same efficacy as non-senescent tMVECs. Intriguingly, GBM CSCs themselves are capable of differentiating into cells with similar features as tMVECs that subsequently undergo senescence when exposed to radiation. This indicates that endothelial-like cells are therapy resistant and, more importantly, support expansion of GBM cell

The cholinergic anti-inflammatory pathway regulates the host response during septic peritonitis

Background. The nervous system, through the vagus nerve, can down-regulate inflammation in vivo by decreasing the release of tumor necrosis factor-a by endotoxin-stimulated macrophages. This anti-inflammatory effect is mediated by an interaction between acetylcholine, the principal neurotransmitter of the vagus nerve, and cholinergic nicotinic acetylcholine receptors on macrophages. Methods. We determined the role of this "cholinergic anti-inflammatory pathway" during septic peritonitis induced in mice by intraperitoneal injection of live Escherichia coli. Septic peritonitis was preceded by inhibition of the cholinergic anti-inflammatory pathway by unilateral cervical vagotomy, by stimulation of this pathway by pretreatment of mice with nicotine, or by a combination of both interventions. Results. Initial cytokine release during septic peritonitis was enhanced after previous vagotomy and was decreased after nicotine pretreatment, independently of the integrity of the vagus nerve. Further study established that vagotomy before septic peritonitis resulted in an enhanced influx of neutrophils and a marked increase in proinflammatory cytokine levels and liver damage. Conversely, nicotine pretreatment strongly decreased cell influx, proinflammatory cytokine levels, and liver damage, whereas bacterial clearance and survival were impaired. Discussion. These data provide the first evidence, to our knowledge, of an important role of the vagus nerve in regulating the innate immune response to a severe bacterial infectio

Therapeutic effects of troglitazone in experimental chronic pancreatitis in mice

Peroxisome proliferator-activated receptor (PPAR)-gamma controls growth, differentiation, and inflammation. PPAR-gamma agonists exert anti-inflammatory effects in vitro and inhibit the activation of pancreas stellate cells, implicated in the formation and progression of fibrosis. We determined the influence of troglitazone, a ligand for PPAR-gamma, on pancreatic damage and fibrosis in experimental chronic pancreatitis. Mice received six hourly intraperitoneal injections with 50 mug/kg of cerulein or saline, three times a week for 6 weeks. One week after the last injection all mice were sacrificed. Untreated mice were compared with mice treated with troglitazone either during weeks 1 to 6 or weeks 4 to 6. All mice that received cerulein injections displayed histopathological signs of chronic pancreatitis at week 7. Troglitazone treatment improved all markers for severity of pancreatitis. Moreover, early and postponed troglitazone treatments were equally effective in diminishing intrapancreatic fibrosis as quantified by Sirius red staining, hydroxyproline content, and laminin staining as well as the increased number of pancreatic stellate cells and pancreas levels of transforming growth factor-beta. Thus, troglitazone attenuated pancreatic damage and inflammation in experimental chronic pancreatitis and remained beneficial in a therapeutic setting when given after initial damage had been establishe