Effects of soluble guanylyl cyclase stimulation on muscle oxygenation and exercise capacity in heart failure with mildly reduced ejection fraction

Figures

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  FIGURE 1. Experimental protocol for exercise measurements, dosing regimen and echocardiography (a) and phosphorescence quenching measurements (b). Created in BioRender. https://BioRender.com/vynpu76. Abbreviations: echo, echocardiogram; BAY 41, BAY 41‐2272.

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  FIGURE 2. Average and individually plotted time to exhaustion. Data are means ± SD. Healthy rats (n = 6), Healthy + BAY41 (n = 7), HFmrEF (n = 7) and HFmrEF + BAY41 (n = 9). Data were analysed via two‐way ANOVA with Tukey's post hoc analyses. # p < 0.001 versus Healthy; *p = 0.006 versus HFmrEF Vehicle. Abbreviations: BAY41, BAY 41‐2272; HFmrEF, heart failure with mildly reduced ejection fraction.

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  FIGURE 3. Spinotrapezius muscle interstitial PO2 response at rest (from −30 to 0 s) and during twitch contractions (0–180 s) for Healthy rats (n = 8), Healthy + BAY41 (n = 8), HFmrEF (n = 7) and HFmrEF + BAY41 (n = 10). Data are means ± SD. The dashed line represents the onset of twitch contractions. (a) HFmrEF + BAY41 rats had a significantly higher PO2is during steady‐state contractions and from 140 to 180 s (blue area) versus HFmrEF vehicle control rats. (b) Healthy + BAY41 rats had a significantly greater PO2is at rest (from −30 to 0 s) and during twitch contractions (30–60 and 90–180 s) (blue areas). The PO2is was compared across time via two‐way repeated‐measures ANOVA with Tukey's post hoc analyses. *p < 0.05 for each 2 s increment versus Vehicle within group. Abbreviations: BAY41, BAY 41‐2272; HFmrEF, heart failure with mildly reduced ejection fraction; PO2is, interstitial PO2.

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  FIGURE 4. Spinotrapezius muscle interstitial PO2 response during SNP superfusion. Data are means ± SD for Healthy rats (n = 8), Healthy + BAY41 (n = 6), HFmrEF (n = 7) and HFmrEF + BAY41 (n = 10). At 0 s (dashed line) SNP was continuously superfused onto the muscle. The incubation period reflects a time for the PO2is response to reach a steady state. (a) HFmrEF + BAY41 rats had a significantly higher PO2is during 78–262 s (blue area) versus HFmrEF vehicle control rats. There was a significant drug × time interaction for the HFmrEF groups (p = 0.013). (b) Healthy + BAY41 rats had a significantly greater PO2is throughout the entire response. The PO2is was compared across time via two‐way repeated‐measures ANOVA with Tukey's post hoc analyses. *p < 0.05 for each 2 s increment versus Vehicle within group. Abbreviations: BAY41, BAY 41‐2272; HFmrEF, heart failure with mildly reduced ejection fraction; PO2is, interstitial PO2 ; SNP, sodium nitroprusside.

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  FIGURE 5. Spinotrapezius muscle interstitial PO2 during contractions after SNP superfusion. Data are means ± SD. The dashed line represents the onset of twitch contractions for Healthy rats (n = 8), Healthy + BAY41 (n = 6), HFmrEF (n = 7) and HFmrEF + BAY41 (n = 10). (a) HFmrEF + BAY41 rats had a significantly higher PO2is during 46–180 s (blue area) versus HFmrEF vehicle control rats. (b) Healthy + BAY41 rats had a significantly greater PO2is throughout the entire response. The PO2is was compared across time via two‐way repeated‐measures ANOVA with Tukey's post hoc analyses. *p < 0.05 for each 2 s increment versus Vehicle within group. Abbreviations: BAY41, BAY 41‐2272; HFmrEF, heart failure with mildly reduced ejection fraction; PO2is, interstitial PO2; SNP, sodium nitroprusside.

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  FIGURE 6. Normalized spinotrapezius muscle interstitial PO2 during twitch contractions in both control (CON, no superfusion; a) and SNP superfusion (b) conditions. The onset of contractions is at 0 s. Data are averaged across animals. Control: Healthy (n = 8), Healthy + BAY41 (n = 8), HFmrEF (n = 7) and HFmrEF + BAY41 (n = 10); and SNP: Healthy (n = 8); Healthy + BAY41 (n = 6); HFmrEF (n = 7) and HFmrEF + BAY41 (n = 10). Error bars are omitted for clarity. (a) There was no significant difference in percentage change within groups during control contraction. (b) SNP slows the kinetic response to contractions in all groups versus control conditions, but to the greatest extent in the BAY41‐treated rats. There was a statistically lower PO2is percentage change in HFmrEF + BAY41 rats during 60–180 s (blue area) and in Healthy + BAY41 rats from 86 to 142 s (blue line). The PO2is was compared across time via two‐way repeated‐measures ANOVA with Tukey's post hoc analyses. *p < 0.05 for each 2 s increment versus Vehicle within group. Abbreviations: BAY41, BAY 41‐2272; HFmrEF, heart failure with mildly reduced ejection fraction; PO2is, interstitial PO2; SNP, sodium nitroprusside.

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  FIGURE 7. Spinotrapezius muscle sGCβ1 (a) and SOD1 (b) protein expression. Data are means ± SD. Twenty‐one samples of spinotrapezius muscle (Healthy, n = 4; Healthy + BAY41, n = 4; HFmrEF, n = 6; HFmrEF + BAY41, n = 7) were used to measure sGCβ1 and SOD1 expression via western immunoblotting. Representative western blot images are presented below each graph. (a) There was a significantly greater expression of sGCβ1 in the spinotrapezius muscle of HFmrEF + BAY41 rats (*p = 0.045). (b) No statistical difference was detected in spinotrapezius muscle SOD1 expression (Healthy, p = 0.932; HFmrEF, p = 0.897). Data were analysed via two‐way mixed‐effects ANOVA and Fisher's least significant difference test without correction for multiple comparisons. Abbreviations: a.u., arbitrary units; BAY41, BAY 41‐2272; HFmrEF, heart failure with mildly reduced ejection fraction; sGCβ1, soluble guanylyl cyclase beta 1 subunit; SOD1, superoxide dismutase 1.