Essential role of hemoglobin beta-93-cysteine in posthypoxia facilitation of breathing in conscious mice

B Gaston, WJ May, S Sullivan… - Journal of Applied …, 2014 - journals.physiology.org
B Gaston, WJ May, S Sullivan, S Yemen, NV Marozkina, LA Palmer, JN Bates, SJ Lewis
Journal of Applied Physiology, 2014journals.physiology.org
When erythrocyte hemoglobin (Hb) is fully saturated with O2, nitric oxide (NO) covalently
binds to the cysteine 93 residue of the Hb β-chain (B93-CYS), forming S-nitrosohemoglobin.
Binding of NO is allosterically coupled to the O2 saturation of Hb. As saturation falls, the NO
group on B93-CYS is transferred to thiols in the erythrocyte, and in the plasma, forming
circulating S-nitrosothiols. Here, we studied whether the changes in ventilation during and
following exposure to a hypoxic challenge were dependent on erythrocytic B93-CYS …
When erythrocyte hemoglobin (Hb) is fully saturated with O2, nitric oxide (NO) covalently binds to the cysteine 93 residue of the Hb β-chain (B93-CYS), forming S-nitrosohemoglobin. Binding of NO is allosterically coupled to the O2 saturation of Hb. As saturation falls, the NO group on B93-CYS is transferred to thiols in the erythrocyte, and in the plasma, forming circulating S-nitrosothiols. Here, we studied whether the changes in ventilation during and following exposure to a hypoxic challenge were dependent on erythrocytic B93-CYS. Studies were performed in conscious mice in which native murine Hb was replaced with human Hb (hB93-CYS mice) and in mice in which murine Hb was replaced with human Hb containing an alanine rather than cysteine at position 93 on the Bchain (hB93-ALA). Both strains expressed human γ-chain Hb, likely allowing a residual element of S-nitrosothiol-dependent signaling. While resting parameters and initial hypoxic (10% O2, 90% N2) ventilatory responses were similar in hB93-CYS mice and hB93-ALA mice, the excitatory ventilatory responses (short-term potentiation) that occurred once the mice were returned to room air were markedly diminished in hB93-ALA mice. Further, short-term potentiation responses were virtually absent in mice with bilateral transection of the carotid sinus nerves. These data demonstrate that hB93-CYS plays an essential role in mediating carotid sinus nerve-dependent short-term potentiation, an important mechanism for recovery from acute hypoxia.
American Physiological Society