Alterations in nitric oxide-dependent sympathetic neurotransmission of peripheral vascular beds of rats with chronic heart failure

Introduction and Hypothesis: Expression of neuronal nitric oxide synthase (nNOS) is decreased in the paraventricular nucleus (PVN) of rats with chronic heart failure (CHF), however the underlying molecular mechanism/s remain unclear. Recently, we demonstrated, Angiotensin II (Ang II) mediated increase in PIN: protein inhibitor of nNOS (0.76±0.10 Sham vs 1.12±0.09* CHF) which is known to down-regulate nNOS through disruption of active dimers (~60% decrease in dimer/monomer ratio) in the PVN of rats with CHF. Functionally impeded monomeric enzyme is degraded by ubiquitin proteasome system. Interestingly, PIN transcript levels remain unchanged in the PVN in CHF (1.00±0.23 Sham vs. 1.1±0.28 CHF). This observation prompted us to elucidate the molecular mechanism for the accumulation of PIN post-transcriptionally in the PVN in CHF Methods and Results: We used coronary artery ligation model of CHF in rats (6-8 weeks past ligation) and neuronal NG108-15 hybrid cell line. PIN translation was inhibited using cyclohexamide (CHX) for 0-4h after 20h of pretreatment with Ang II in NG108 cells. CHX mediated decrease in PIN expression was ameliorated with Ang II (0.19±0.04 vs 0.41±0.06* 4h). Proteasome inhibitor lactacystin (LC) treatment dramatically elevates PIN level suggesting the involvement of proteasome system in PIN regulation. Immunoprecipitation with ubiquitin antibody showed decrease PIN-Ub conjugates in Ang II-treated cells (1.04 ± 0.05 LC vs. 0.62 ± 0.07* LC AngII). In vitro ubiquitination assay in cells transfected with pCMV-(HA-Ub)8 vector revealed reduction of HA-Ub-PIN conjugates after Ang II treatment (9.2 ± 2.2 LC vs. 4.5 ± 0.6* LC Ang II). Furthermore, there was decreased accumulation of PIN-Ub conjugates in the PVN of CHF rats compared to Sham as revealed by immunohistochemistry. Conclusions: Taken together, our studies revealed that PIN is targeted for rapid degradation by the ubiquitin-proteasome pathway and Ang II delays the rate of degradation resulting in accumulation of PIN. We conclude that post-translational accumulation of PIN, mediated by Ang II, leads to a decrease in the dimeric active form of nNOS as well as protein levels of nNOS, which may lead to reduced nitric oxide resulting in over-activation of sympathetic drive during CHF.

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Serum uric acid (UA) in cachectic and non-cachectic chronic heart failure (CHF) patients - Relation to peripheral vascular resistance (PVR)

European Journal of Heart Failure ◽

10.1016/s1388-9842(00)80234-2 ◽

2000 ◽

Vol 2 ◽

pp. 65-65

Author(s):

W. Doehner ◽

C.H. Davos ◽

M. Rauchhaus ◽

R. Sharma ◽

A. Bolger ◽

...

Keyword(s):

Heart Failure ◽

Uric Acid ◽

Chronic Heart Failure ◽

Serum Uric Acid ◽

Vascular Resistance ◽

Peripheral Vascular Resistance ◽

Peripheral Vascular

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Increased l-arginine Transport in Human Erythrocytes in Chronic Heart Failure

Clinical Science ◽

10.1042/cs0940043 ◽

1998 ◽

Vol 94 (1) ◽

pp. 43-48 ◽

Cited By ~ 20

Author(s):

H. Hanssen ◽

T. M. C. Brunini ◽

M. Conway ◽

A. P. Banning ◽

N. B. Roberts ◽

...

Keyword(s):

Nitric Oxide ◽

Heart Failure ◽

Chronic Heart Failure ◽

Human Erythrocytes ◽

Transport Systems ◽

Acid Transport ◽

Cationic Amino Acid ◽

Arginine Transport ◽

Healthy Donors ◽

Patients With Heart Failure

1. Transport of l-arginine was investigated under zero-trans conditions in human erythrocytes from healthy donors and patients with heart failure. 2. Saturable influx of l-arginine was mediated by the classical cationic amino acid transport systems y+ and y+L. 3. The Vmax for l-arginine transport via system y+ increased from 292 to 490 μmol h−-1 l−-1 of cells in heart failure. 4. With system y+ inhibited by N-ethylmaleimide (0.2 mmol/l), the Vmax for the transport of l-arginine via system y+L was unaffected in erythrocytes from patients with heart failure. 5. The inhibition of l-arginine and l-leucine influx by NG-monomethyl-l-arginine was similar in erythrocytes from control and heart failure patients. 6. Plasma l-arginine levels were reduced in patients with heart failure (59 μmol/l) compared with controls (125 μmol/l). Plasma from patients with heart failure also contained the endogenous l-arginine analogue NG-monomethyl-l-arginine, which was undetectable in plasma from controls. 7. Intracellular concentrations of l-arginine and NG-monomethyl-l-arginine were significantly elevated in erythrocytes from patients with heart failure compared with controls, consistent with an increased transport capacity for l-arginine and NG-monomethyl-l-arginine. 8. The present study provides the first evidence that system y+ mediates the increased transport of l-arginine in human erythrocytes from patients with chronic heart failure. These findings are similar to our previous results obtained in patients with chronic renal failure. Since both pathologies seem to present with an increased synthesis of nitric oxide, studies of l-arginine transport in erythrocytes may provide a valuable paradigm to study abnormalities of the l-arginine-nitric oxide signalling pathway.

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