p65BTK Is a Novel Biomarker and Therapeutic Target in Solid Tumors.

Bruton's tyrosine kinase (BTK) is a non-receptor intracellular kinase playing a key role in the proliferation and survival of normal and malignant B-lymphocytes. Its targeting by Ibrutinib, the first specific inhibitor, represented a turning point for the therapy of certain types of B-cell leukemias/lymphomas and several more BTK inhibitors are today in the clinic or advanced clinical trials. BTK expression was successively found to occur also outside of the hematopoietic compartment. In fact, we identified p65BTK, a novel 65 kDa isoform lacking an N-term stretch of 86 amino acids (compared to the 77 kDa protein expressed in B cells) as highly expressed in colon cancer patients. We demonstrated that p65BTK is a powerful oncogene acting downstream of the RAS/MAPK pathway and necessary for RAS-mediated transformation. Notably, the kinase domain is conserved and therefore inhibited by the available BTK-targeting drugs (Ibrutinib, Spebrutinib, etc.) which we used to demonstrate that p65BTK is an actionable target in drug-resistant colorectal carcinomas. We found p65BTK expressed also in >50% non-small cell lung cancers (NSCLC) and demonstrated that it is an actionable target in KRAS-mutated/EGFR-wild type drug-resistant NSCLC models (for which no targeted therapy is available). We also reported a significant correlation between p65BTK expression and low-grade tumors and overall survival of patients with grade III gliomas and showed that its targeting induced a significant decrease in the viability of in glioma stem cells. Finally, in ovarian cancer patients, p65BTK expression levels correlate with early relapse and shorter progression-free survival, both indicators of resistance to therapy. Remarkably, Ibrutinib is more effective than standard of care (SOC) therapeutics in in vitro and ex vivo settings. On the whole, our preclinical data indicate that, depending on the tumor type, BTK inhibitors used alone can induce cytotoxicity (gliomas), be more effective than SOC chemotherapy (ovarian cancer) or can kill drug-resistant tumor cells when used in combination with SOC chemotherapy (colon cancer and NSCLC) or targeted therapy (NSCLC and ovarian cancer), thus suggesting that p65BTK may be an actionable target in different solid tumors. In addition, our data also give the proof-of-concept for starting clinical trials using BTK inhibitors, alone or in combination, to improve the therapeutic options for solid tumors treatment.

BTK inhibitors synergise with 5-FU to treat drug-resistant TP53-null colon cancers.

Colorectal cancer (CRC) is the fourth cause of death from cancer worldwide mainly due to the high incidence of drug-resistance. During a screen for new actionable targets in drug-resistant tumours we recently identified p65BTK - a novel oncogenic isoform of Bruton's tyrosine kinase. Studying three different cohorts of patients here we show that p65BTK expression correlates with histotype and cancer progression. Using drug-resistant TP53-null colon cancer cells as a model we demonstrated that p65BTK silencing or chemical inhibition overcame the 5-fluorouracil resistance of CRC cell lines and patient-derived organoids and significantly reduced the growth of xenografted tumours. Mechanistically, we show that blocking p65BTK in drug-resistant cells abolished a 5-FU-elicited TGFB1 protective response and triggered E2F-dependent apoptosis. Taken together, our data demonstrated that targeting p65BTK restores the apoptotic response to chemotherapy of drug-resistant CRCs and gives a proof-of-concept for suggesting the use of BTK inhibitors in combination with 5-FU as a novel therapeutic approach in CRC patients. © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

p65BTK is a novel potential actionable target in KRAS-mutated/EGFR-wild type lung adenocarcinoma.

BACKGROUND: Lung cancer is still the main cause of cancer death worldwide despite the availability of targeted therapies and immune-checkpoint inhibitors combined with chemotherapy. Cancer cell heterogeneity and primary or acquired resistance mechanisms cause the elusive behaviour of this cancer and new biomarkers and active drugs are urgently needed to overcome these limitations. p65BTK, a novel isoform of the Bruton Tyrosine Kinase may represent a new actionable target in non-small cell lung cancer (NSCLC). METHODS: p65BTK expression was evaluated by immunohistochemistry in 382 NSCLC patients with complete clinico-pathological records including smoking habit, ALK and EGFR status, and in metastatic lymph nodes of 30 NSCLC patients. NSCLC cell lines mutated for p53 and/or a component of the RAS/MAPK pathway and primary lung cancer-derived cells from Kras/Trp53 null mice were used as a preclinical model. The effects of p65BTK inhibition by BTK Tyrosine Kinase Inhibitors (TKIs) (Ibrutinib, AVL-292, RN486) and first-generation EGFR-TKIs (Gefitinib, Erlotinib) on cell viability were evaluated by MTT. The effects of BTK-TKIs on cell growth and clonogenicity were assessed by crystal violet and colony assays, respectively. Cell toxicity assays were performed to study the effect of the combination of non-toxic concentrations of BTK-TKIs with EGFR-TKIs and standard-of-care (SOC) chemotherapy (Cisplatin, Gemcitabine, Pemetrexed). RESULTS: p65BTK was significantly over-expressed in EGFR-wild type (wt) adenocarcinomas (AdC) from non-smoker patients and its expression was also preserved at the metastatic site. p65BTK was also over-expressed in cell lines mutated for KRAS or for a component of the RAS/MAPK pathway and in tumors from Kras/Trp53 null mice. BTK-TKIs were more effective than EGFR-TKIs in decreasing cancer cell viability and significantly impaired cell proliferation and clonogenicity. Moreover, non-toxic doses of BTK-TKIs re-sensitized drug-resistant NSCLC cell lines to both target- and SOC therapy, independently from EGFR/KRAS status. CONCLUSIONS: p65BTK results as an emerging actionable target in non-smoking EGFR-wt AdC, also at advanced stages of disease. Notably, these patients are not eligible for EGFR-TKIs-based therapy due to a lack of EGFR mutation. The combination of BTK-TKIs with EGFR-TKIs is cytotoxic for EGFR-wt/KRAS-mutant/p53-null tumors and BTK-TKIs re-sensitizes drug-resistant NSCLC to SOC chemotherapy. Therefore, our data suggest that adding BTK-TKIs to SOC chemotherapy and EGFR-targeted therapy may open new avenues for clinical trials in currently untreatable NSCLC.

Metronomic combination of Vinorelbine and 5Fluorouracil is able to inhibit triple-negative breast cancer cells. Results from the proof-of-concept VICTOR-0 study.

Triple Negative Breast Cancer (TNBC) is an aggressive neoplasia with median Overall Survival (OS) less than two years. Despite the availability of new drugs, the chance of survival of these patients did not increase. The combination of low doses of drugs in a metronomic schedule showed efficacy in clinical trials, exhibiting an anti-proliferative and anti-tumour activity. In Victor-2 study we recently evaluated a new metronomic combination (mCHT) of Capecitabine (CAPE) and Vinorelbine (VNR) in breast cancer patients showing a disease control rate with a median Progression-Free Survival (PFS) of 4.7 months in 28 TNBC patients. Here in Victor-0 study, we examined the effect of mCHT vs standard (STD) schedule of administration of different combinations of 5-Fluorouracil (5FU), the active metabolite of CAPE, and VNR in TNBC cell lines MDA-MB-231 and BT-549. A significant anti-proliferative activity was observed in cells treated with metronomic vs STD administration of 5FU or VNR alone. Combination of the two drugs showed an additive inhibitor effect on cell growth in both cell lines. Moreover, after exposure of cells to 5FU and VNR under mCHT or conventional schedule of administration we also observed a downregulation of chemoresistance factor Bcl-2, changes in pro-apoptotic protein Bax and in cleaved effector caspase-3 and increased expression of LC3A/B autophagy protein. Our results therefore suggest that molecular mechanisms implicated in apoptosis and autophagy as well as the cross-talk between these two forms of cell death in MDA-MB-231 and BT-549 cells treated with 5FU and VNR is dose- and schedule-dependent and provide some insights about the roles of autophagy and senescence in 5FU/VNR-induced cell death.

GSK3A is redundant with GSK3B in modulating drug resistance and chemotherapy-induced necroptosis.

Glycogen Synthase Kinase-3 alpha (GSK3A) and beta (GSK3B) isoforms are encoded by distinct genes, are 98% identical within their kinase domain and perform similar functions in several settings; however, they are not completely redundant and, depending on the cell type and differentiative status, they also play unique roles. We recently identified a role for GSK3B in drug resistance by demonstrating that its inhibition enables necroptosis in response to chemotherapy in p53-null drug-resistant colon carcinoma cells. We report here that, similarly to GSK3B, also GSK3A silencing/inhibition does not affect cell proliferation or cell cycle but only abolishes growth after treatment with DNA-damaging chemotherapy. In particular, blocking GSK3A impairs DNA repair upon exposure to DNA-damaging drugs. As a consequence, p53-null cells overcome their inability to undergo apoptosis and mount a necroptotic response, characterized by absence of caspase activation and RIP1-independent, PARP-dependent AIF nuclear re-localization. We therefore conclude that GSK3A is redundant with GSK3B in regulating drug-resistance and chemotherapy-induced necroptosis and suggest that inhibition of only one isoform, or rather partial inhibition of overall cellular GSK3 activity, is enough to re-sensitize drug-resistant cells to chemotherapy.

Severely obese adolescents and adults exhibit a different association of circulating levels of adipokines and leukocyte expression of the related receptors with insulin resistance.

Obese adults frequently exhibit a low-grade inflammation and insulin resistance, which have been hypothesized to be established early in childhood. Aim of this study was to evaluate the age-dependent relationships between inflammatory state and insulin resistance in obese adolescents and adults. Clinical and metabolic parameters, circulating adipokines (TNF- α , adiponectin, and leptin), ghrelin, their leukocyte receptors (TNFR1, ADIPOR2, OBRL and GHSR1a), and acute phase reactants (CRP and white blood cells) were assessed in lean and obese adolescents compared with the adult counterparts. Only obese adults had higher HOMA-IR, insulin, and triglycerides compared to the lean group. An inflammatory state was present in obese adolescents and adults, as demonstrated by the higher values of CRP and neutrophils. There were no group differences in circulating levels of TNF- α and leukocyte expression of TNFR1. Adiponectin concentrations and leukocyte expression of ADIPOR2 were higher in the lean groups than in the corresponding obese counterparts. For leptin and leukocyte expression of OBRL, the results were opposed. Circulating levels of ghrelin were higher in lean adolescents and adults than the related lean groups, while there was a higher leukocyte expression of GHSR1a in (only) lean adults than obese adults. When the analysis was performed in (lean or obese) adults, TNF- α , neutrophils, leptin, and GHSR1a were predictors of HOMA-IR. None of the considered independent variables accounted for the degree of insulin resistance in the adolescent group. In conclusion, a dissociation between the low-grade inflammation and insulin resistance is supposed to exist in the early phases of obesity.

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.

Effect of somatostatin infusion on peptide YY secretion: studies in the acute and recovery phase of anorexia nervosa and in obesity.

OBJECTIVE: Changes in many gastrointestinal peptides, including the anorexigenic peptide YY (PYY), which is produced by L cells, occur in both anorexia nervosa (AN) and obesity (OB). High PYY levels are present in AN, whereas in morbid OB fasting and postprandial PYY secretion is blunted. Somatostatin (somatotropin release-inhibiting factor (SRIF)) reportedly inhibits plasma PYY concentrations in animals and healthy humans, but the effect of a SRIF infusion on spontaneous PYY secretion in AN and OB is unknown. METHODS: A total of 18 young women, seven with acute AN (A-AN), four with AN in the recovery phase (R-AN), and seven with morbid OB, were studied. All subjects underwent an infusion of SRIF (9 µg/kg i.v./h, over 60 min), with blood samples drawn before and at different time intervals after SRIF administration. Plasma PYY levels were measured at each time point. RESULTS: SRIF significantly inhibited plasma PYY concentrations in R-AN and OB, without affecting PYY titers in A-AN. In OB, the inhibitory effect of SRIF also persisted at 90 min. Withdrawal of SRIF infusion in R-AN resulted in a prompt restoration of basal plasma PYY levels, whereas termination of SRIF infusion in OB was followed by a slower increase of PYY titers toward baseline levels. After infusion, PYY Δ area under the curve (ΔAUC) in R-AN was significantly higher than those in A-AN and OB patients. A significant difference in PYY ΔAUC between A-AN and OB was present. CONCLUSIONS: These results suggest the existence of a hypo- and hyper-sensitivity of L cells to the inhibitory effect of SRIF in A-AN and OB respectively.

Asymmetric dimethylarginine (ADMA) induces vascular endothelium impairment and aggravates post-ischemic ventricular dysfunction in rats.

Asymmetric dimethylarginine (ADMA) is an endogenous nitric oxide (NO) inhibitor recognized as an independent risk factor for endothelial dysfunction and coronary heart diseases. This study investigated whether ADMA (10 mg/kg day for 14 days) affected endothelial function and aggravated post-ischemic ventricular dysfunction in the perfused rat heart. Systolic blood pressure and heart rate, plasma levels of ADMA and nitrite/nitrate were measured in vehicle- and ADMA-treated rats. Perfused hearts were submitted to global ischemia-reperfusion and vascular endothelial dysfunction was examined with angiotensin II in coronary vessels and aortic rings. Endothelial NO synthase (eNOS) and angiotensin-converting enzyme (ACE) mRNA expression in aortic and cardiac tissues were measured. ADMA-treated rats had higher systolic blood pressure (1.3-fold, P<0.01) and slower heart rate (16%, P<0.05) than controls. Plasma ADMA rose (1.9-fold, P<0.01) and nitrite/nitrate concentration decreased 59% (P<0.001). Ventricular contraction (stiffness) increased significantly, with worsening of post-ischemic ventricular dysfunction. In preparations from ADMA-treated rats the coronary vasculature's response to angiotensin II was almost doubled (P<0.01) and the maximal vasorelaxant effect of acetylcholine in aortic rings was significantly lower than in preparations from vehicle-treated rats. In cardiac and aortic tissues eNOS mRNA and ACE mRNA levels were similar in controls and ADMA-treated rats. The increased plasma levels of ADMA presumably cause endothelial dysfunction because of a deficiency in NO production, which also appears involved in the aggravation of myocardial ischemia-reperfusion injury.

Testosterone inhibition of growth hormone release stimulated by a growth hormone secretagogue: studies in the rat and dog.

Anabolic steroids are frequently taken by athletes and bodybuilders together with recombinant human GH (rhGH), though there is some scientific evidence that the use of anabolic steroids reverses the rhGH-induced effects. Recently, we have shown that treatment with rhGH (0.2 IU/kg s.c., daily x 12 days) in the dog markedly reduced the canine GH (cGH) responses stimulated by EP51216, a GH secretagogue (GHS), evaluated after 3 and 5 daily rhGH injections, and that the inhibition was still present a few days after rhGH discontinuation. The aim of the present study was to evaluate in the dog the GH response to EP51216 (125 mug/kg i.v.) in a condition of enhanced androgenic function (i.e. acute injection or 15-day treatment with testosterone at the dose of 2 mg/kg i.m. on alternate days), and in the hypophysectomized rat the hypothalamic and hippocampal expression of ghrelin, the receptor of GHSs (GHS-R), GH-releasing hormone (GHRH) and somatostatin (SS) after specific hormonal replacement therapies (testosterone, 1 mg/kg/day s.c.; hydrocortisone, 500 mug/kg/day s.c.; rhGH, 400 mug/kg/day s.c.; 0.9% saline 0.1 ml/kg/day s.c.; x11 days). In the dog experiments, under baseline conditions, a single injection of EP51216 elicited an abrupt rise of plasma cGH. Twenty-four hours from the acute bolus injection of testosterone, C(max) and AUC(0-90) of the GHS-stimulated cGH response were significantly lower than baseline cGH response; 5 days later, there was still a significant decrease of either parameter versus the original values. Short-term treatment with testosterone markedly reduced the GHS-stimulated cGH responses evaluated during (5th bolus) and at the end (8th bolus) of testosterone treatment. Four and 8 days after testosterone withdrawal, the EP51216-stimulated cGH response was still significantly reduced when compared with that under baseline conditions. Plasma concentrations of insulin-like growth factor 1 (IGF-1) were stable until the 5th bolus of testosterone and decreased progressively in the remaining time of the testosterone treatment; 4 and 8 days from treatment withdrawal, IGF-1 levels were still suppressed. In rat studies, hypothalamic mRNA levels of GHS-R were significantly reduced by treatments with testosterone and hydrocortisone, whereas hippocampal expressions of ghrelin, GHRH and SS were reduced by rhGH replacement therapy. In conclusion, these studies show that a single administration of testosterone can abrogate the cGH response ensuing acute stimulation by a GHS; the inhibitory effect of testosterone on the cGH response to GHS is present during and even 8 days after termination of a short-lived treatment with testosterone; these events occur via a

Early tolerance to the hypophagic effect of the cannabinoid receptor antagonist SR141716 does not impede blockade of an orexigenic stimulus.

The cannabinoid CB1 receptor antagonist SR141716 (Rimonabant) is known to reduce food intake by central and peripheral mechanisms. Recently, SR141716 has been reported to block the orexigenic effect of ghrelin, a potent orexigenic peptide produced by the stomach. This study investigated whether in rats, made tolerant to the hypophagic effect of SR141716, the drug was still capable to block the orexigenic activity of another non-natural (hypothalamic) peptide, i.e., the growth hormone releasing peptide (GHRP) hexarelin, a ghrelin mimetic. In the acute experiments, each dose of SR141716 (1, 5 and 10 mg/kg i.p.) reduced food intake with respect to vehicle-treated rats, whereas hexarelin (160 microg/kg s.c.) markedly stimulated feeding. All doses of SR141716 were capable to reduce the orexigenic effect of the GHRP. A 15-day administration of SR141716 (10 mg/kg i.p.) reduced both food intake and body weight. Tolerance to the hypophagic effect of SR141716 developed within 5 days, but in contrast, body weight remained markedly below that of vehicle-treated group throughout the entire treatment period. Interestingly, despite development of tolerance to its hypophagic effect, SR141716 was capable to suppress the orexigenic effect of repeated hexarelin challenge tests performed throughout the chronic experiments. In conclusion, the results of the present study confirm and broaden the existence of a functional relationship between ghrelin and endocannabinoids in the control of food intake, and bespeak the ability of a CB1 receptor antagonist to suppress orexia caused by stimuli alien to direct stimulation of the cannabinoid system.

Orexigenic effects of a growth hormone secretagogue and nitric oxide in aged rats and dogs: correlation with the hypothalamic expression of some neuropeptidergic/receptorial effectors mediating food intake.

Hypothalamic neurochemical alterations in mammals underlie disturbances of food intake. There is scarce information on these topics in elderly persons; therefore, the aims of the present study were: (i) to evaluate the orexigenic effects of a growth hormone secretagogue, administered to young and old rats and dogs, alone or in combination with molsidomine, a donor of nitric oxide and (ii) to evaluate by reverse transcription-polymerase chain reaction in the whole hypothalamus of young and old rats messenger RNA levels of a wide number of anabolic and catabolic peptides, receptors, and enzymes involved in the control of feeding behavior, relating the detected titers, whenever possible, to the feeding responses to growth hormone secretagogue. In all, the results obtained strengthen the proposition that, in the hypothalamus of old rats, anti-anorexigenic compensatory mechanisms are operative, aimed at maintaining a "normal" feeding pattern. Thus, the occurrence of a primary, age-related alteration in the feeding mechanisms is unlikely.

Angiotensin II type 1 receptor antagonism improves endothelial vasodilator function in L-NAME-induced hypertensive rats by a kinin-dependent mechanism.

OBJECTIVE: This study was designed to investigate the ability of a chronic blockade of angiotensin II type 1 receptors with losartan to reverse the endothelial dysfunction present in N-nitro-L-arginine methyl ester (L-NAME)-treated hypertensive rats and the possible dependence of this effect on bradykinin B2-receptor activation. METHODS: Rats treated with L-NAME alone (60 mg/kg per day for 8 weeks) or with L-NAME + losartan, L-NAME + icatibant (a bradykinin B2-receptor antagonist) and L-NAME + losartan + icatibant were studied. Losartan, icatibant or losartan + icatibant were co-administered with L-NAME during the last 4 weeks of the experiment. Endothelial nitric oxide synthase gene expression in aortic tissues, plasma nitrite/nitrate concentrations, the relaxant effect of acetylcholine on norepinephrine-precontracted aortic rings and 6-keto-PGF1alpha release from aortic rings were used as markers of the endothelial function. RESULTS: Rats treated with L-NAME alone and L-NAME + icatibant showed, as compared with untreated animals, a clear-cut increase in systolic blood pressure and a decrease of all the markers of endothelial function evaluated. In L-NAME-rats, administration of losartan reduced the systolic blood pressure and restored endothelial nitric oxide synthase gene expression, plasma nitrite/nitrate levels, the relaxant activity of acetylcholine on aortic rings and the generation of 6-keto-PGF1alpha from the aortic tissues. Co-administration of icatibant with losartan blunted the stimulatory effect of losartan on the markers of endothelial function evaluated. CONCLUSION: These results demonstrated that losartan is capable of reversing the endothelial vasodilator dysfunction in L-NAME-induced hypertensive rats, and that the beneficial effect of losartan is mediated by bradykinin B2-receptor activation.

Angiotensin-converting enzyme inhibition and angiotensin AT1-receptor antagonism equally improve endothelial vasodilator function in L-NAME-induced hypertensive rats.

Male Sprague-Dawley rats given N(omega)-nitro-L-arginine methyl ester (L-NAME) in drinking water for 8 weeks showed: (1) a clear-cut increase in systolic blood pressure; (2) a consistent decrease of endothelial-cell nitric oxide synthase (eNOS) gene expression in aortic tissue; (3) a marked reduction of plasma nitrite/nitrate concentrations; (4) a reduction of the relaxant activity of acetylcholine (ACh, from 10(-10) to 10(-4) M) on norepinephrine-precontracted aortic rings (reduction by 48+/-5%); (5) a marked decrease (-58%) of the basal release of 6-keto-prostaglandin F1alpha (6-keto-PGF1alpha) from aortic rings. In L-NAME-treated rats, administration in the last 4 weeks of either the angiotensin-converting enzyme (ACE) inhibitor enalapril (10 mg/kg/day in tap water) or the angiotensin AT(1)-receptor antagonist losartan (10 mg/kg/day in tap water) decreased systolic blood pressure levels, completely restored eNOS mRNA levels in aortic tissue and plasma nitrite/nitrate levels, and allowed a consistent recovery of both the relaxant activity of acetylcholine and the generation of 6-keto-PGF1alpha. Coadministration of icatibant, a bradykinin B(2)-receptor antagonist (200 microg/kg/day), with enalapril blunted the stimulatory effect of the ACE inhibitor on eNOS mRNA expression, circulating levels of nitrite/nitrate, the relaxant activity of ACh and the release of 6-keto-PGF1alpha in L-NAME-treated rats. The generation of 6-keto-PGF1alpha from aortic rings was also decreased in rats coadministered icatibant with losartan. These findings indicate that (1) the ACE inhibitor enalapril and the angiotensin AT(1)-receptor blocker losartan are equally effective to reverse NAME-induced endothelial dysfunction; (2) the beneficial effect of enalapril on the endothelial vasodilator function in L-NAME-treated rats is mediated by bradykinin B(2)-receptor activation; and (3) the enhanced endothelial generation of prostacyclin induced by losartan in L-NAME rats is also mediated by bradykinin B(2)-receptor activation.

Molsidomine antagonizes L-NAME-induced acquisition deficits in a recognition memory task in the rat.

The present study was designed to investigate the role of nitric oxide (NO) on the acquisition of a recognition memory task in the rat. For this purpose, the effects on memory exerted by pre-training administration of the NO synthase inhibitor L-NAME (N(omega)-nitro-L-arginine methyl ester) and the NO donor molsidomine (N-[ethoxycarbonyl]-3-[4-morpholinosydnomine]) were assessed by using the object recognition task, a working memory paradigm based on the differential exploration of a new and familiar object. In a first dose-response study, it was found that L-NAME (10, 30, and 60 mg kg(-1), i.p.) at 30 but not at 10 mg kg(-1) disrupted animals performance, whereas the dose of 60 mg kg(-1) induced side effects. Molsidomine (2 and 4 mg kg(-1), i.p.) at 4 but not at 2 mg kg(-1), antagonized the L-NAME-induced performance deficits. These results indicate that NO is involved in the acquisition of a recognition memory task.

Enalapril and quinapril improve endothelial vasodilator function and aortic eNOS gene expression in L-NAME-treated rats.

Endothelial dysfunction ensuing inhibition of nitric oxide synthase (NOS) was investigated in male Sprague-Dawley rats given N(omega)-nitro-L-arginine methyl ester (L-NAME) in drinking water for 8 weeks. Age-matched rats served as controls. L-NAME-treated rats, as compared to control animals, showed: (1) a clear-cut increase in systolic blood pressure; (2) a consistent decrease of endothelial-cell NOS (eNOS) gene expression in aortic tissue; (3) a reduction of the relaxant activity of acetylcholine (ACh, from 10(-10) to 10(-4) M) on norepinephrine-precontracted aortic rings (reduction by 52+/-5%); (4) a marked decrease (-50%) of the basal release of 6-keto-prostaglandin F(1 alpha) (6-keto-PGF(1 alpha)) from aortic rings. In L-NAME-treated rats, administration in the last 2 weeks of either the angiotensin-converting enzyme inhibitor enalapril (1 mg/kg/day) or the cognate drug quinapril (1 mg/kg/day) decreased systolic blood pressure levels, completely restored eNOS mRNA levels in aortic tissue, and allowed a consistent recovery of both the relaxant activity of ACh and the generation of 6-keto-PGF(1 alpha). No difference was present in the ability of the two angiotensin-converting enzyme inhibitors to reverse NAME-induced endothelial dysfunction. These findings indicate that L-NAME-induced hypertension in the rat relies on the marked impairment of the endothelial vasodilator function, with an ensuing contribution by a decreased production of prostacyclin by the endothelial cells. Angiotensin-converting enzyme inhibition by enalapril or quinapril was equally effective in improving endothelial vasodilator function, prostacyclin endothelial production and restoring aortic eNOS mRNA.