Abstract
BackgroundSickle cell disease patients display priapism that may progress to erectile dysfunction. However, little is known about the pathophysiological alterations of corpus cavernosum in sickle cell disease.ObjectiveThus, this study aimed to evaluate the functional and molecular alterations of sympathetic machinery and nitric oxide—cyclic guanosine monophosphate signaling pathway in Townes transgenic sickle cell disease mice.MethodsConcentration–response curves to contractile (phenylephrine) and relaxant agents (acetylcholine and sodium nitroprusside) were obtained in corpus cavernosum strips from sickle and C57BL/6 (control) mice. Neurogenic contractions and nitrergic relaxations were obtained using electrical-field stimulation. Measurements of endothelial nitric oxide synthase (eNOS), neuronal nitric oxide synthase (nNOS), phosphodiesterase-5 (PDE5) and α1A-, α1B- and α1D-adrenoceptor mRNA expressions and reactive-oxygen species were performed. Tyrosine hydroxylase phosphorylated at Ser-31 and total tyrosine hydroxylase protein expressions in cavernosal tissues were also measured.ResultsThe neurogenic contractions were higher in the sickle cell disease group, in association with elevated tyrosine hydroxylase phosphorylated at Ser-31 and total tyrosine hydroxylase protein expression, as well as increased tyrosine hydroxylase mRNA expression. Likewise, phenylephrine-induced contractions were greater in the sickle mice, whereas α1A-, α1B- and α1D-adrenoceptor mRNA expression remained unchanged. Cavernosal relaxations to acetylcholine, sodium nitroprusside and EFS were higher in sickle mice, accompanied by decreased eNOS and nNOS, along with lower PDE5 mRNA expression. An increase of about 40% in reactive-oxygen species generation in corpus cavernosum from sickle mice was also detected.ConclusionOur study shows that decreased nitric oxide bioavailability in erectile tissue due to increased oxidative stress leads to both sympathetic hyperactivity and dysregulation of nitric oxide signaling in corpus cavernosum from Townes sickle mice.
Highlights
Sickle cell disease (SCD), an inherited disorder of hemoglobin production, is a disorder of polymerization of hemoglobin S (HbS)
The neurogenic contractions were higher in the sickle cell disease group, in association with elevated tyrosine hydroxylase phosphorylated at Ser-31 and total tyrosine hydroxylase protein expression, as well as increased tyrosine hydroxylase mRNA expression
Cavernosal relaxations to acetylcholine, sodium nitroprusside and Electrical-field stimulation (EFS) were higher in sickle mice, accompanied by decreased endothelial nitric oxide synthase (eNOS) and neuronal nitric oxide synthase (nNOS), along with lower PDE5 mRNA expression
Summary
Sickle cell disease (SCD), an inherited disorder of hemoglobin production, is a disorder of polymerization of hemoglobin S (HbS). Polymerization HbS within erythrocytes causes stiffness of red blood cells, resulting in hemolysis, vaso-occlusive crisis, stroke, pulmonary hypertension, osteonecrosis and leg ulcers [1]. Transgenic sickle cell mice have been employed to better understand the complex pathophysiology of SCD. The homozygous Townes transgenic sickle cell mouse is another model for SCD that was developed by the replacement of the mouse α-globin genes by human α-globin genes, while the mouse β-globin genes are replaced by human Aγ and βS (sickle) globin genes [3]. Homozygous Townes SCD mice develop disease symptoms such as severe anemia due to erythrocyte sickling, splenic infarcts, renal damage, liver damage, vaso-occlusion and urine concentration defects [3]. Sickle cell disease patients display priapism that may progress to erectile dysfunction. Little is known about the pathophysiological alterations of corpus cavernosum in sickle cell disease.
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