Muscle-Specific Calpastatin Overexpression Prevents Diaphragm Weakness in Cecal Ligation Puncture-Induced Sepsis
Recent work indicates that infections are a major contributor to diaphragm weakness in patients who are critically ill and mechanically ventilated, and that diaphragm weakness is a risk factor for death and prolonged mechanical ventilation. Infections activate muscle calpain, but many believe this is an epiphenomenon and that other proteolytic processes are responsible for infection-induced muscle weakness. We tested the hypothesis that muscle-specific overexpression of calpastatin (CalpOX; an endogenous calpain inhibitor) would attenuate diaphragm dysfunction in cecal ligation puncture (CLP)-induced sepsis. We studied 1) wild-type (WT) sham-operated mice, 2) WT CLP-operated mice, 3) CalpOX sham-operated mice, and 4) CalpOX CLP-operated mice (n = 9-10/group). Twenty-four hours after surgery, we assessed the diaphragm force-frequency relationship, diaphragm mass, and total protein content and diaphragm levels of talin and myosin heavy chain (MHC). CLP markedly reduced diaphragm-specific force generation (force/cross-sectional area), which was prevented by calpastatin overexpression (force averaged 21.4 ± 0.5, 6.9 ± 0.8, 22.4 ± 1.0, and 18.3 ± 1.3 N/cm2, respectively, for WT sham, WT CLP, CalpOX sham, and CalpOX CLP groups, P < 0.001). Diaphragm mass and total protein content were similar in all groups. CLP induced talin cleavage and reduced MHC levels; CalpOX prevented these alterations. CLP-induced sepsis rapidly reduces diaphragm-specific force generation and is associated with cleavage and/or depletion of key muscle proteins (talin, MHC), effects prevented by muscle-specific calpastatin overexpression. These data indicate that calpain activation is a major cause of diaphragm weakness in response to CLP-induced sepsis.
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This work was supported by National Heart, Lung, and Blood Institute Grants R01 HL-113494, R01 HL-080429, and R01 HL-081525 to G.S.S., and R01 HL-112085 to L.A.C.
Supinski, Gerald S.; Wang, Lin; Song, Xiao-Hong; Moylan, Jennifer S.; and Callahan, Leigh Ann, "Muscle-Specific Calpastatin Overexpression Prevents Diaphragm Weakness in Cecal Ligation Puncture-Induced Sepsis" (2014). Internal Medicine Faculty Publications. 62.