Introduction: A component of multiorgan dysfunction in burned patients is heart failure. Burn trauma has been shown to induce cytokine synthesis of IL-6, IL-1-beta, and TNF-alpha which can negatively impact cardiac function. We examined the effect of burn injury and lipopolysaccharide (LPS) exposure on cardiomyocyte contraction and cytokine secretion.

Methods: Rats underwent a full-thickness 30%TBSA scald or sham burn. At 1,6,12 and 24 hours post-burn cardiomyocytes were isolated, plated at 50,000 cells/well, and incubated with 0, 1, 10, 25, and 50 micrograms/ml LPS for 18 hours. Supernatants were assayed by ELISA for IL-6, IL-1-beta, and TNF-alpha. Sarcomere length during contraction was recorded using a variable rate video camera with length detection software.

Results: Peak relative sarcomere shortening was decreased in the burn vs. sham group at 1, 6, 12, and 24 hours post-burn (p < 0.003, ANOVA). Exposure of cardiomyocytes to LPS resulted in a decrease in sarcomere shortening at 1, 6, 12, and 24 hours independent of burn status (p < 0.03, ANOVA). Cytokine secretion was not increased by exposure to LPS. IL-6, IL-1-beta, and TNF-alpha levels were increased in cardiomyocytes harvested 1 hour post-burn compared to sham controls (p < 0.05, t-test). There was no difference in cytokine levels between the burn and sham group at 6, 12, and 24 hours post-burn regardless of LPS dose.

-

Hr  LPS ug/ml  IL-6 pg/ml  IL-1 pg/ml  TNF alpha pg/ml  Sham  Burn  Sham  Burn  Sham  Burn  1  0  389 ± 32  942 ± 209  46 ± 13  111 ± 9  32 ± 5  53 ± 2  1  389 ± 44  988 ± 195  47 ± 14  105 ± 12  33 ± 5  55 ± 4  10  349 ± 43  937 ± 172  45 ± 9  104 ± 10  32 ± 5  50 ± 3  25  365 ± 49  979 ± 207  51 ± 12  109 ± 13  32 ± 5  53 ± 4  50  351 ± 39  1070 ± 253  46 ± 7  114 ± 16  32 ± 5  53 ± 5  6  0  523 ± 81  453 ± 44  41 ± 8  47 ± 7  27 ± 1  28 ± 4  1  492 ± 78  420 ± 54  43 ± 11  48 ± 8  25 ± 0  28 ± 4  10  543 ± 98  483 ± 48  31 ± 3  44 ± 7  26 ± 1  28 ± 4  25  577 ± 101  466 ± 67  45 ± 10  65 ± 11  26 ± 1  28 ± 4  50  526 ± 97  448 ± 44  39 ± 7  56 ± 10  25 ± 1  28 ± 4  12  0  743 ± 161  882 ± 167  50 ± 11  29 ± 4  24 ± 0  24 ± 0  1  765 ± 170  884 ± 164  49 ± 10  26 ± 1  24 ± 0  24 ± 0  10  757 ± 172  917 ± 161  50 ± 10  29 ± 4  24 ± 0  24 ± 0  25  788 ± 179  945 ± 192  52 ± 11  36 ± 6  24 ± 0  24 ± 0  50  752 ± 169  818 ± 131  41 ± 6  39 ± 7  24 ± 0  24 ± 0  24  0  119 ± 43  259 ± 66  25 ± 0  34 ± 9  37 ± 8  38 ± 6  1  80 ± 26  312 ± 56  27 ± 2  25 ± 0  36 ± 7  38 ± 6  10  129 ± 73  304 ± 62  27 ± 2  34 ± 6  35 ± 6  38 ± 6  25  143 ± 70  246 ± 80  28 ± 3  35 ± 9  35 ± 6  38 ± 6  50  113 ± 51  200 ± 46  25 ± 0  34 ± 9  35 ± 6  38 ± 6

[]

Conclusions: Burn injury diminished peak sarcomere shortening. LPS inhibits sarcomere shortening in a dose-dependent fashion where cytokine levels are increased in cardiomyocytes 1 hour post-burn, this difference is abolished at 6, 12, and 24 hours. Exposure of cardiomyocytes to LPS does not have an effect on cytokine synthesis.