Role of protein tyrosine phosphatase 1B in cardiovascular diseases.

Protein Tyrosine Phosphatase 1B (PTP1B) is mostly involved in negative regulation of signaling mediated by Tyrosine Kinase Receptors, especially the insulin and leptin receptors. This enzyme thus plays a major role in the development of diseases associated with insulin resistance, such as obesity and diabetes. PTP1B inhibition is currently considered as an attractive treatment of insulin resistance and associated metabolic disorders. In parallel, emerging evidence also suggests that PTP1B is widely expressed in cardiovascular tissues, notably in the heart and the endothelium, and that it could also be a potential treatment of several cardiovascular diseases. PTP1B is especially present in endothelial cells, and appears to contribute to endothelial dysfunction. Indeed, preclinical evidence shows that pharmacological inhibition of gene deletion of PTP1B reduces endothelial dysfunction in various cardiovascular diseases associated or not with insulin resistance. In parallel, because PTP1B also negatively modulates VEGF signaling, inhibition of this enzyme also tends to favor cardiac angiogenesis. Importantly, blocking PTP1B also results in beneficial effects on cardiac dysfunction and remodeling not only in metabolic diseases but also in the context of heart failure, thus this enzyme represents an attractive new target for the treatment of this disease. This beneficial effect in heart failure may to a large extent result from the endothelial protective and/or proangiogenic effects of PTP1B blockade. Finally, PTP1B inhibition also reduces cardiac dysfunction, but also systemic inflammation and mortality in experimental models of septic shock, and thus may also constitute a new treatment of this disease. Altogether, accumulating preclinical evidence suggests that PTP1B represents an interesting molecular target to treat both cardiovascular and metabolic diseases, which often share the same risk factors. This concept now deserves to be tested in clinical studies that should soon be possible with the current development of selective PTP1B inhibitors.

Gene deletion of protein tyrosine phosphatase 1B protects against sepsis-induced cardiovascular dysfunction and mortality.

OBJECTIVE: Cardiovascular dysfunction is a major cause of mortality in patients with sepsis. Recently, we showed that gene deletion or pharmacological inhibition of protein tyrosine phosphatase 1B (PTP1B) improves endothelial dysfunction and reduces the severity of experimental heart failure. However, the cardiovascular effect of PTP1B invalidation in sepsis is unknown. Thus, we explored the beneficial therapeutic effect of PTP1B gene deletion on lipopolysaccharide (LPS)-induced cardiovascular dysfunction, inflammation, and mortality. APPROACH AND RESULTS: PTP1B(-/-) or wild-type mice received LPS (15 mg/kg) or vehicle followed by subcutaneous fluid resuscitation (saline, 30 mL/kg). α-1-dependent constriction and endothelium-dependent dilatation, assessed on isolated perfused mesenteric arteries, were impaired 8 hours after LPS and significantly improved in PTP1B(-/-) mice. This was associated with reduced vascular expression of interleukin1-ß, intercellular adhesion molecule-1, vascular cell adhesion molecule-1, cyclooxygenase-2, and inducible nitric oxide synthase mRNA. PTP1B gene deletion also limited LPS-induced cardiac dysfunction assessed by echocardiography, left ventricular pressure-volume curves, and in isolated perfused hearts. PTP1B(-/-) mice also displayed reduced LPS-induced cardiac expression of tumor necrosis factor-α, interleukin1-ß, intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and Gp91phox, as well as of several markers of cellular infiltration. PTP1B deficiency also reduced cardiac P38 and extracellular signal-regulated protein kinase 1 and 2 phosphorylation and increased phospholamban phosphorylation. Finally, PTP1B(-/-) mice displayed a markedly reduced LPS-induced mortality, an effect also observed using a pharmacological PTP1B inhibitor. PTP1B deletion also improved survival in a cecal ligation puncture model of sepsis. CONCLUSIONS: PTP1B gene deletion protects against septic shock-induced cardiovascular dysfunction and mortality, and this may be the result of the profound reduction of cardiovascular inflammation. PTP1B is an attractive target for the treatment of sepsis.

Reduction of heart failure by pharmacological inhibition or gene deletion of protein tyrosine phosphatase 1B.

Protein tyrosine phosphatase 1B (PTP1B) regulates tyrosine kinase receptor-mediated responses, and especially negatively influences insulin sensitivity, thus PTP1B inhibitors (PTP1Bi) are currently evaluated in the context of diabetes. We recently revealed another important target for PTP1Bi, consisting in endothelial protection. The present study was designed to test whether reduction of PTP1B activity may be beneficial in chronic heart failure (CHF). We evaluated the impact of either a 2 month pharmacological inhibition, or a gene deletion of PTP1B (PTP1B(-/-)) in CHF mice (2 months post-myocardial infarction). PTP1Bi and PTP1B deficiency reduced adverse LV remodeling, and improved LV function, as shown by the increased LV fractional shortening and cardiac output (measured by echocardiography), the increased LV end systolic pressure, and the decreased LV end diastolic pressure, at identical infarct sizes. This was accompanied by reduced cardiac fibrosis, myocyte hypertrophy and cardiac expression of ANP. In vitro vascular studies performed in small mesenteric artery segments showed a restored endothelial function (i.e. improved NO-dependent, flow-mediated dilatation, increased eNOS phosphorylation) after either pharmacological inhibition or gene deletion. PTP1B(-/-) CHF also displayed an improved insulin sensitivity (assessed by euglycemic-hyperinsulinemic clamp studies), when compared to wild-type CHF associated with an increased insulin mediated mesenteric artery dilation. Thus, chronic pharmacological inhibition or gene deletion of PTP1B improves cardiac dysfunction and cardiac remodeling in the absence of changes in infarct size. Thus this enzyme may be a new therapeutic target in CHF. Diabetic patients with cardiac complications may potentially benefit from PTP1B inhibition via two different mechanisms, reduced diabetic complications, and reduced heart failure.

Arteriogenic therapy by intramyocardial sustained delivery of a novel growth factor combination prevents chronic heart failure.

BACKGROUND: Therapeutic angiogenesis is a promising approach for the treatment of cardiovascular diseases, including myocardial infarction and chronic heart failure. We aimed to improve proangiogenic therapies by identifying novel arteriogenic growth factor combinations, developing injectable delivery systems for spatiotemporally controlled growth factor release, and evaluating functional consequences of targeted intramyocardial growth factor delivery in chronic heart failure. METHODS AND RESULTS: First, we observed that fibroblast growth factor and hepatocyte growth factor synergistically stimulate vascular cell migration and proliferation in vitro. Using 2 in vivo angiogenesis assays (n=5 mice per group), we found that the growth factor combination results in a more potent and durable angiogenic response than either growth factor used alone. Furthermore, we determined that the molecular mechanisms involve potentiation of Akt and mitogen-activated protein kinase signal transduction pathways, as well as upregulation of angiogenic growth factor receptors. Next, we developed crosslinked albumin-alginate microcapsules that sequentially release fibroblast growth factor-2 and hepatocyte growth factor. Finally, in a rat model of chronic heart failure induced by coronary ligation (n=14 to 15 rats per group), we found that intramyocardial slow release of fibroblast growth factor-2 with hepatocyte growth factor potently stimulates angiogenesis and arteriogenesis and prevents cardiac hypertrophy and fibrosis, as determined by immunohistochemistry, leading to improved cardiac perfusion after 3 months, as shown by magnetic resonance imaging. These multiple beneficial effects resulted in reduced adverse cardiac remodeling and improved left ventricular function, as revealed by echocardiography. CONCLUSION: Our data showing the selective advantage of using fibroblast growth factor-2 together with hepatocyte growth factor suggest that this growth factor combination may constitute an efficient novel treatment for chronic heart failure.

Characterization of the initial complaint and care pathways prior to diagnosis in very young sporadic Alzheimer's disease.

BACKGROUND: Very-early-onset Alzheimer's disease (young-AD) differentiates from late-onset AD (old-AD) by a predominant involvement of the parietal neocortex leading to atypical presentations. The diagnosis of AD is often not the first to be mentioned in such young patients. METHODS: We retrospectively reviewed the initial complaint and care pathways of 66 sporadic young-AD (age < 62) and 30 old-AD patients (age > 65) and compared their neuropsychological profiles at the time of diagnosis (based on clinical-biological criteria) with 44 amyloid-negative controls. RESULTS: The initial complaint of young-AD was non-cognitive and mimicked a burnout in 32% of cases. Their main cognitive complaints were memory (38% vs 87% in old-AD) and language (17% vs 13%) impairment. The referral to a psychiatrist prior to AD diagnosis was more frequent in young-AD than in old-AD (26% vs 0%). At the time of diagnosis, young-AD were at a more severe stage of dementia than old-AD (24% vs 10% with CDR ≥ 1) but had less anosognosia. CONCLUSIONS: Better identifying the initial signs of very-early-onset AD is crucial to improve the early diagnosis and develop new treatments.

[New pharmacological approaches in heart failure: should we treat the endothelium?]. / Nouvelles voies pharmacologiques dans l'insuffisance cardiaque: faut-il traiter l'endothélium?

Heart failure is associated with endothelial dysfunction, characterized especially by a decreased nitric oxide (NO) production. The main consequences of this dysfunction appear to be: 1) at the coronary level, an altered myocardial perfusion associated with increased cardiac metabolic demand and, 2) at the peripheral level, an increased arterial resistance leading to increased afterload and cardiac work. Such an endothelial dysfunction may thus contribute to aggravate heart failure and represents an important pharmacological target in this disease. Indeed, these endothelial alterations may be reduced by "classic" treatments of heart failure (e.g. inhibitors of the renin angiotensin aldosterone system), as well as more recent approaches (e.g. ivabradine). Moreover, new approaches have been recently developed to specifically target the endothelial NO production, for example via inhibition of protein tyrosine phosphatase 1B, that may ultimately lead to new treatment of heart failure based on endothelial protection.

Executive and social-cognitive determinants of environmental dependency syndrome in behavioral frontotemporal dementia.

OBJECTIVE: Environmental dependency syndrome (EDS), including utilization (UB) and imitation (IB) behaviors, is often reported in behavioral variant frontotemporal dementia (bvFTD). These behaviors are commonly attributed to executive dysfunction. However, inconsistent associations between EDS and poor executive performance has led to an alternative "social hypothesis," instead implicating patients' misinterpretation of the examiner's intention. We investigated the possible explanatory cognitive mechanisms of EDS in bvFTD by relating UB and IB to performance on tests of executive functioning and theory of mind (ToM). METHOD: This study analyzed retrospective data of 32 bvFTD patients. Data included scores of UB and IB, various executive measures, and ToM assessment using the faux pas test, from which we extracted a mental attribution score. RESULTS: Of the patients, 15.6% and 40.6% exhibited UB and IB, respectively. We conducted an automatic linear modeling analysis with executive and mental attribution measures as predictor variables, and UB and IB sequentially considered as target variables. ToM mental attribution score, visual abstraction and flexibility measures from the Wisconsin Card Sorting Test, and motor sequence performance significantly (corrected ps < .05) predicted IB. No executive or ToM measures significantly predicted UB. CONCLUSIONS: These findings reveal a complex interaction between executive dysfunction and mental attribution deficits influencing the prevalence of EDS in bvFTD. Further investigation is required to improve our understanding of the mechanisms underlying these behaviors. (PsycINFO Database Record

Selective Vascular Endothelial Protection Reduces Cardiac Dysfunction in Chronic Heart Failure.

BACKGROUND: Chronic heart failure (CHF) induces endothelial dysfunction in part because of decreased nitric oxide (NO(·)) production, but the direct link between endothelial dysfunction and aggravation of CHF is not directly established. We previously reported that increased NO production via inhibition of protein tyrosine phosphatase 1B (PTP1B) is associated with reduced cardiac dysfunction in CHF. Investigation of the role of endothelial PTP1B in these effects may provide direct evidence of the link between endothelial dysfunction and CHF. METHODS AND RESULTS: Endothelial deletion of PTP1B was obtained by crossing LoxP-PTP1B with Tie2-Cre mice. CHF was assessed 4 months after myocardial infarction. In some experiments, to exclude gene extinction in hematopoietic cells, Tie2-Cre/LoxP-PTP1B mice were lethally irradiated and reconstituted with bone marrow from wild-type mice, to obtain mouse with endothelial-specific deletion of PTP1B. Vascular function evaluated ex vivo in mesenteric arteries showed that in wild-type mice, CHF markedly impaired NO-dependent flow-mediated dilatation. CHF-induced endothelial dysfunction was less marked in endoPTP1B(-/-) mice, suggesting restored NO production. Echocardiographic, hemodynamic, and histological evaluations demonstrated that the selectively improved endothelial function was associated with reduced left ventricular dysfunction and remodeling, as well as increased survival, in the absence of signs of stimulated angiogenesis or increased cardiac perfusion. CONCLUSIONS: Prevention of endothelial dysfunction, by endothelial PTP1B deficiency, is sufficient to reduce cardiac dysfunction post myocardial infarction. Our results provide for the first time a direct demonstration that endothelial protection per se reduces CHF and further suggest a causal role for endothelial dysfunction in CHF development.

Effortless control: executive attention and conscious feeling of mental effort are dissociable.

Recruitment of executive attention is normally associated to a subjective feeling of mental effort. Here we investigate the nature of this coupling in a patient with a left mesio-frontal cortex lesion including the anterior cingulate cortex (ACC), and in a group of comparison subjects using a Stroop paradigm. We show that in normal subjects, subjective increases in effort associated with executive control correlate with higher skin-conductance responses (SCRs). However, our patient experienced no conscious feeling of mental effort and showed no SCR, in spite of exhibiting normal executive control, and residual right anterior cingulate activity measured with event-related potentials (ERPs). Finally, this patient demonstrated a pattern of impaired behavior and SCRs in the Iowa gambling task-elaborated by Damasio, Bechara and colleagues-replicating the findings reported by these authors for other patients with mesio-frontal lesions. Taken together, these results call for a theoretical refinement by revealing a decoupling between conscious cognitive control and consciously reportable feelings. Moreover, they reveal a fundamental distinction, observed here within the same patient, between the cognitive operations which are depending on normal somatic marker processing, and those which are withstanding to impairments of this system.

Subtle cognitive impairment but no dementia in patients with spastin mutations.

BACKGROUND: The most frequent form of autosomal dominant hereditary spastic paraparesis is associated with the SPG4 locus, described originally as a pure form of the disease. Mutations of the SPG4 gene have been increasingly associated with reports of cognitive impairment. OBJECTIVE: To investigate cognitive function in 10 families with hereditary spastic paraparesis due to mutations in the SPG4 gene, using intrafamilial control subjects. PATIENTS AND METHODS: Neuropsychological examinations, including the Cambridge Cognitive Evaluation, were conducted in 29 carriers with identified SPG4 mutations and 29 intrafamilial controls. RESULTS: Carriers were not demented but had a subclinical cognitive impairment primarily affecting executive functions. The dysfunction was more severe in those carriers older than 50 years, but was correlated with the progression of the disease, not with age. Disease progression and cognitive impairment appeared to be more severe in the carriers of missense mutations than in those with truncating mutations. CONCLUSION: Asymptomatic cognitive impairment mostly affecting executive functions is present in SPG4 mutation carriers and is more frequent in those with missense mutations.

Soluble epoxide hydrolase inhibition prevents coronary endothelial dysfunction in mice with renovascular hypertension.

OBJECTIVES: The study addresses the hypothesis that endothelial dysfunction in experimental arterial hypertension can be related to an alteration in epoxyeicosatrienoic acids (EETs) pathway and can be prevented by the inhibition of EETs degradation by soluble epoxide hydrolase (sEH). METHODS AND RESULTS: Arterial hypertension was induced in FVB/N mice by renal artery stenosis ('two-kidney-one-clip', 2K1C). Seven weeks after surgery, increased aortic pressures (Millar tonometer; Millar Instruments, Houston, Texas, USA) and cardiac hypertrophy (echocardiography) were present in 2K1C mice as compared with control mice. Left coronary artery endothelium-dependent relaxations to acetylcholine were decreased in 2K1C mice without modification in the relaxing responses to NS309 and NS1619, the openers of calcium-activated potassium channels mediating the hyperpolarizing effect of EETs. The inhibitors of the EET-synthesizing enzymes cytochrome P450 epoxygenases, fluconazole and N-methylsulfonyl-6-(2-propargyloxyphenyl)-hexanamide (MSPPOH), reduced the coronary relaxations to acetylcholine in control but not in 2K1C mice. The sEH expression was increased in 2K1C mice. The sEH inhibitor 12-(3-adamantan-1-yl-ureido)dodecanoic acid administered for 2 weeks starting 5 weeks after surgery in 2K1C mice (25 mg/l in drinking water) reduced aortic pressures and cardiac hypertrophy, improved the coronary relaxations to acetylcholine and restored the inhibitory effect of fluconazole and MSPPOH on acetylcholine-induced relaxations, without modifying the relaxations to NS309 and NS1619. CONCLUSION: These results demonstrate that a reduced EET-mediated relaxations related to an increased degradation by sEH contributes to coronary endothelial dysfunction in 2K1C hypertensive mice. Inhibiting sEH prevents endothelial dysfunction by restoring EET-mediated relaxations and thus, could represent a promising pharmacological intervention to limit cardiovascular morbidity and mortality in arterial hypertension.

Aging and prostacyclin responses in aorta and platelets from WKY and SHR rats.

In spontaneously hypertensive rat (SHR) aorta, prostacyclin is an endothelium-derived contracting factor contributing to the endothelial dysfunction. This study was designed to determine whether the impairment of the prostacyclin response is influenced by aging and whether such a dysfunction is observed in platelets. Isometric tension was measured in aortic rings, and aggregation was studied in platelet-rich plasma taken from 3-, 6-, and 15-mo-old Wistar-Kyoto rats (WKY) and SHR. In aorta from 3- and 6-mo-old WKY, prostacyclin and beraprost [prostacyclin receptor (IP) agonists] produced relaxations that were enhanced by Triplion (thromboxane-prostanoid receptor antagonist). In 15-mo-old WKY, the relaxations to beraprost were maintained, but not those to prostacyclin. In SHR aorta, prostacyclin or beraprost produced no or minor relaxations, which, in younger SHR, were enhanced by Triplion. In both strains, the relaxations were inhibited by CAY-10441 (IP receptor antagonist). The relaxations to forskolin and isoproterenol were reduced with aging. When compared with those of WKY, the relaxations to isoproterenol were reduced in 3- but not in 6- or 15-mo-old SHR, whereas those to forskolin were consistently diminished at any given age. Whatever the age, prostacyclin and beraprost produced CAY-10441-sensitive inhibitions of ADP-induced platelet aggregation. Both agonists were more potent in SHR than in WKY. Therefore, in platelets from WKY and SHR, the IP receptor-dependent antiaggregant response is functional and maintained during aging. In aorta from WKY those responses are reduced by aging and, in SHR, are already compromised at 3 mo. This dysfunction of the IP receptor is only partially explained by a general dysfunction of the adenylate cyclase pathway.