We have shown previously that acute,
in vitro
inhibition of protein tyrosine phosphatase 1B (PTP1B) improved endothelial function of peripheral resistance arteries in mice with chronic heart failure (CHF), as demonstrated by the restored flow-mediated, NO-dependent vasodila-tation (FMD). This is most likely due to increased tyrosine phosphorylation pathways involved in shear stress-induced activation of eNOS. The present study evaluates the impact of
chronic
pharmacological inhibition or genetic disruption of PTP1B, on cardiac and endothelial dysfunction in CHF mice. CHF was induced by coronary ligation, either in C57BL/6 mice, or in wild type (WT) or PTP1B-deficient (PTP1B−/−) BALB/c mice. CHF mice (either C57BL/6 or BALB/c WT) were untreated or treated with the PTP1B inhibitor AS279 (60 mg/kg/day) for 2 months. Mice were then anesthetized with isoflurane for echocardiographic evaluation of left ventricular (LV) function and remodeling. After euthanasia, small mesenteric artery segments were isolated and mounted in an arteriograph for the evaluation of FMD. Echocardiographic results are shown in the Table
. In parallel,
in vitro
vascular studies showed that chronic AS279 restored FMD both in C57BL/6 (max FMD: control: 17±2, n=9; CHF untreated: -1±1, n=9; CHF + AS279: 14±2%, n=19; p<0.01 vs. CHF untreated) and BALB/c CHF mice (Control: 29±4, n=16; CHF untreated: 7±1, n=5; CHF + AS279: 24±6%, n=7; p<0.01 vs. CHF untreated). Compared to CHF WT, FMD was also increased in PTP1B−/− CHF mice (WT: 7±1, n=5, PTP1B−/−: 16±6%, n=6, p<0.05). Additionally,
in vitro
downregulation of PTP1B (by a 3 day incubation with shRNA) also increased FMD in arteries isolated from CHF mice (max FMD: untreated: 6±2; scrambled shRNA: 7±2; shRNA PTP1B: 27±2%, p<0.01). Thus, chronic pharmacological inhibition or genetic disruption of PTP1B both restores endothelial function and improves cardiac dysfunction and remodeling, suggesting that this enzyme may be a new target for the treatment of CHF.
Echocardiographic results in mice with 2 months CHF
Comment on ‘Pharmacological inhibition of protein tyrosine phosphatase 1B protects against atherosclerotic plaque formation in the LDLR−/− mouse model of atherosclerosis’
