Transforming growth factor-beta1 blocks in vitro cardiac myocyte depression induced by tumor necrosis factor-alpha, interleukin-1beta, and human septic shock serum.

OBJECTIVE: Serum from patients with septic shock induces depression of myocyte contractility in vitro that is proportional the reduction of ejection fraction in vivo. This effect is mediated, in part, by tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta. Transforming growth factor (TGF)-beta is an immunomodulatory cytokine with a broad range of anti-inflammatory effects. Using an in vitro assay, this study sought to determine the effect of TGF-beta1 on myocyte depression induced by TNF-alpha, IL-1beta, and serum with known depressant activity from patients with septic shock. DESIGN: The maximum extent of shortening of electrically paced rat cardiac myocytes in tissue culture was quantified by a closed-loop video tracking system. Myocytes were exposed to different combinations of TNF-alpha, IL-1beta, septic serum, and TGF-beta1. SETTING: Basic research laboratory. MEASUREMENTS AND MAIN RESULTS: Increasing concentrations of TNF-alpha and IL-1beta each caused significant depression of maximum extent of myocyte shortening in vitro over 30 mins (p<.0001). Similarly, a synergistic combination of TNF-alpha and IL-1beta as well as serum with known depressant activity from five patients with acute septic shock induced significant depression of cardiac myocyte contraction (p<.01). Increasing concentrations of TGF-beta1 alone had no effect on maximum extent of cardiac myocyte contraction. However, myocytes that were co-incubated with increasing concentrations of TGF-beta1 demonstrated dose-dependent reversal of depression induced by TNF-alpha or IL-1beta (p<.0001). Similarly, depressant effects caused by synergistic concentrations of TNF-alpha and IL-1beta and serum from all five patients with septic shock were prevented by co-incubation with TGF-beta1. CONCLUSIONS: These data demonstrate that depression of in vitro cardiac myocyte contraction induced by proinflammatory cytokines and septic serum can be blocked by TGF-beta1. TGF-beta1 may have potential as therapy for sepsis-associated myocardial depression in humans.

Nitric oxide-dependent and -independent mechanisms are involved in TNF-alpha -induced depression of cardiac myocyte contractility.

Previous studies have demonstrated the presence of myocardial depression in clinical and experimental septic shock. This response is mediated, in part, through circulating TNF-alpha-induced, nitric oxide-dependent, depression of basal myocyte contractility. Other mechanisms of early myocardial dysfunction involving decreased response to adrenergic stimulation may exist. This study evaluated the presence and nitric oxide dependence of impaired adrenergic response to TNF-alpha in in vitro cardiac myocytes. The contraction of electrically paced neonatal rat cardiac myocytes in tissue culture was quantified using a closed-loop video tracking system. TNF-alpha induced depression of baseline contractility over the first 20 min of cardiac myocyte exposure. This effect was blocked by N-methyl-arginine (NMA), a nitric oxide synthase inhibitor, in all studies. Contractile and cAMP response to increasing concentrations of isoproterenol was deficient in cardiac myocytes exposed to TNF-alpha regardless of the presence of NMA. In contrast, increasing concentrations of forskolin (a direct stimulant of adenylate cyclase) and dibutyryl cAMP (a metabolically active membrane-soluble analog of cAMP) completely reversed TNF-alpha-mediated depression, though only in the presence of NMA. Forskolin-stimulated cAMP generation remained intact regardless of NMA. Increasing concentrations of exogenous calcium chloride, unlike other inotropic agents, corrected TNF-alpha-mediated defects of contractility independent of the presence of NMA. These data suggest that TNF-alpha exposure is associated with a second nitric oxide-independent but calcium-dependent early depressant mechanism that is manifested by reduced contractile and cAMP response to beta-adrenergic stimulation.

The duration of hypotension before the initiation of antibiotic treatment is a critical determinant of survival in a murine model of Escherichia coli septic shock: association with serum lactate and inflammatory cytokine levels.

BACKGROUND: This study was designed to examine the relationship between the timing of antibiotic treatment and both survival rates and hemodynamic/inflammatory correlates of survival in a murine model of Escherichia coli septic shock. METHODS: Surgical implantation of an E. coli (O18:K1:H7)-laced, gelatin capsule-encased fibrinogen clot was used to generate a bacteremic model of murine septic shock. Survival duration, hemodynamic responses, and circulating serum tumor necrosis factor (TNF)-alpha , interleukin (IL)-6, and lactate levels were assessed in relation to increasing delays in or absence of antibiotic treatment. RESULTS: A critical inflection point with respect to survival occurred between 12 and 15 h after implantation. When initiated at or before 12 h, antibiotic treatment resulted in < or = 20% mortality, but, when initiated at or after 15 h, it resulted in >85% mortality. Physiologically relevant hypotension developed in untreated septic mice by 12 h after implantation. Values for heart rate differed between untreated septic mice and sham-infected control mice by 6 h after implantation, whereas values for cardiac output and stroke volume did not differ until at least 18-24 h after implantation. Antibiotic treatment initiated > or = 12 h after implantation was associated with persistence of increased circulating serum lactate, TNF- alpha , and IL-6 levels. CONCLUSIONS: The timing of antibiotic treatment relative to hypotension is closely associated with survival in this murine model of septic shock. Delay in antibiotic treatment results in the persistence of inflammatory/stress markers even after antibiotic treatment is initiated.

Bacterial DNA and RNA induce rat cardiac myocyte contraction depression in vitro.

Sepsis and septic shock, the systemic immunologic and pathophysiologic response to overwhelming infection, are associated with perturbation of a variety of metabolic cell pathways and with multiple organ failure (MOF) including cardiac depression. This depression has been attributed to the effect of several circulating and locally produced proinflammatory mediators. Recent data suggest that bacterial nucleic acids can produce profound systemic inflammatory responses characterized by circulatory shock in intact animals. In this study, bacterial DNA and RNA derived from pathogenic clinical S. aureus and E. coli isolates are shown to induce early concentration-dependent depression of maximum extent and peak velocity of contraction of electrically paced neonatal rat ventricular myocytes in culture. Significant but more modest depression was generated by a nonpathogenic E. coli isolate. Pretreatment with a DNase or RNase abrogated this effect. Further, synthetic, double-stranded RNA (dsRNA) also induced concentration-dependent depression of myocyte contraction, with the effect also being prevented by pretreatment with RNase. These data suggest that bacterial DNA and RNA may contribute to myocardial depression during bacterial sepsis and septic shock.