Introduction Remote ischaemic preconditioning (rIPC) is postulated to involve the generation of a humoral signal possibly involving an endothelial signalling pathway. Our lab and others have demonstrated the cardioprotective effects of serum collected from healthy volunteers subjected to rIPC of an arm. This study aims to determine whether cardioprotection from rIPC is preserved in menopause given its association with endothelial and vascular dysfunction, and whether cardioprotection can be restored with oestrogen replacement therapy (ORT).
Methods Blood was taken from healthy male and female volunteers and menopausal women before and after 3 months ORT, after 4 cycles of 5 min of upper arm cuff inflation/deflation and the isolated rIPC-serum applied to adult ventricular myocytes (AVM) for 30 mins to simulate rIPC. Ischaemia/reperfusion injury was induced in AVM by incubating cells in a hypoxic chamber (99.5% N2; 0.5% O2), removal of metabolic substrates and the addition of 2-deoxyglucose (10 mM), for 150 mins. Reperfusion was achieved by the addition of pyruvate (5 mM) and reoxygenation for 60 mins. Cell injury was assessed using calcein and propidium iodide staining and fluorescence microscopy. All serum samples were repeated 3–4 × . Data are mean ± s.e.m. Statistical analysis performed using one-way ANOVA, with Tukey’s test; significance taken at p < 0.05.
Results Hypoxia/reoxygenation resulted in necrotic injury in control AVM of 58.7 ± 2.3% (n = 36) and this was significantly reduced to 35.1 ± 3.3% (n = 20; p < 0.0001) by male and to 36.1 ± 2.4% (n = 24; p < 0.0001) by female rIC-serum. Protection was also seen in AVM treated with serum collected prior to the 4 cycles of conditioning in females at 38.4 ± 3.1% (n = 24; p < 0.0001), but this was less effective in males at 43.5 ± 3.1% (n = 20; p < 0.05). rIC-serum from menopausal women had no significant effect on necrotic injury either before 55.8 ± 3.3% or after 55.1 ± 3.0% (n = 30; NS) conditioning of the arm. There was a small but insignificant improvement following ORT at 51.8 ± 3.4% and 51.2 ± 3.1% respectively (n = 30; NS).
Conclusions Our data show significant cardioprotection by rIC-serum from healthy male and female volunteers. This cardioprotection is absent in women with long standing menopause (>1 yr). ORT over 3 months results in some recovery of cardioprotection but this was not significant. This suggests that although ORT improves endothelium-dependent vasodilatory function,1 it may not improve other endothelial or vascular functions important for rIPC. It is possible that baseline oestrogen levels are responsible for greater cardioprotection seen in healthy female serum collected before rIPC.
Reference 1 Lieberman EH, Gerhard MD, Uehata A, Walsh BW, Selwyn AP, Ganz P, et al. Estrogen Improves Endothelium-Dependent, Flow-Mediated Vasodilation in Postmenopausal Women. Annals of Internal Medicine 1994 December 15;121(12):936–941
- remote ischaemic preconditioning