Caspase‐3 Knockdown Maintained norepinephrine‐mediated Contractility of Adult Rat Ventricular Myocyte during Sepsis

Abstract

We hypothesized that norepinephrine (NE)‐induced upregulation of caspase‐3 is responsible for limiting its efficacy as a positive inotrope during sepsis. Therefore, we determined the effect of NE on the contractile function of adult rat ventricular myocytes (ARVM) transfected with caspase‐3 small interfering RNA (caspase‐3 siRNA). Single ARVMs were isolated from septic/sham hearts obtained from male Sprague‐Dawley rats (350‐400g). The effect of NE was determined in caspase‐3 siRNA‐, non‐silencing RNA‐ transfected sham and septic ARVMs. NE produced a significant but less pronounced increase in peak shortening (PS) in septic ARVMs compared to the sham ARVMs. NE exacerbated the sepsis‐induced upregulated expression of caspase‐3 in ARVMs. NE downregulated caspase‐3 fluorescence and increased PS in caspase‐3 siRNA‐transfected septic ARVMs. Caspase‐3 knockdown in the septic ARVMs increased the expression of the contractile proteins, decreased the release of cytochrome c and number of TUNEL‐positive ARVMs. The data suggest that caspase‐3 knockdown ameliorated decreased contractile response of NE during sepsis and demonstrated the regulatory role of caspase‐3 in ARVM contractile dysfunction.