Comparative evaluation of the usability of 2 different methods to perform mild hypothermia in patients with out-of-hospital cardiac arrest.

BACKGROUND: Several studies have shown that mild hypothermia (32-34°C) markedly mitigates brain damage after cardiac arrest (CA). This study aimed to compare the efficacy of the non-invasive cooling device Hilotherm Clinic (Hilotherm GmbH, Germany) with conventional cooling to induce and maintain mild hypothermia in patients after out-of-hospital CA. METHODS: 50 adult patients with an indication for controlled mild hypothermia were prospectively assigned to conventional cooling (n=20) or cooling with the Hilotherm system (n=30). Patients receiving a cooling therapy by Hilotherm were treated either with 0.35 m(2) (n=20) or with 0.7 m(2) (n=10) surface area of cooling sleeves. RESULTS: The speed of cooling was significantly higher in both Hilotherm groups compared to conventional cooling (Hilotherm 0.7 m(2): 0.91 ± 0.08°C/h, Hilotherm 0.35 m(2): 0.47 ± 0.04°C/h, and conventional: 0.3 ± 0.04°C/h, p ≤ 0.003). Temperature deviation from the target temperature of 33°C was significantly higher in the conventional group compared to both Hilotherm groups. During induction of mild hypothermia a significant reduction of the mean arterial blood pressure and the heart rate was observed without significant differences between the groups. However, the speed of cooling (range 0.3-0.91°C/h) did not correlate to the decrease of blood pressure and heart rate. Norepinephrine dosing during induction of mild hypothermia and re-warming (1st-2nd day) was significantly increased compared to the 3rd day after admission in all groups. Dobutamine dosing and 30 days in-hospital mortality did not differ significantly between the groups. CONCLUSIONS: Rapid and reliable mild hypothermia can be better achieved by the non-invasive cooling system Hilotherm compared to conventional cooling with ice packs and cold infusion.

Survival and quality of life in patients with cardiac resynchronization therapy for severe heart failure and in heart transplant recipients within a contemporary heart failure management program.

BACKGROUND: Current treatment of advanced chronic heart failure comprises pharmacologic approaches, multidisciplinary management strategies and device therapy. We sought to compare the outcome after cardiac synchronization therapy (CRT) with the outcome after heart transplantation within a contemporary heart failure management program. METHODS: In a cohort study, survival and quality of life were assessed in 105 patients who had received CRT (53% with defibrillator) for severe heart failure and in 112 heart transplant recipients attending a heart failure clinic at a tertiary hospital. For assessment of health-related quality of life the Medical Outcome Short Form 36 (SF-36) was applied to the survivors. A propensity score for receiving transplantation vs CRT was developed using logistic regression and was incorporated into statistical models. RESULTS: Severity of heart failure before heart transplantation or CRT was similar. Survival was not different between device recipients and transplant recipients by Kaplan-Meier analysis. Cox regression analysis with time-dependent covariates revealed a significant interaction between treatment and time, which favored transplantation late after intervention. There were no significant differences in 7 of 8 subjective measures of health-related quality of life. The score for physical functioning was higher in the transplantation group; this difference remained of borderline significance after multivariate adjustment. CONCLUSIONS: Contemporary management of patients with advanced heart failure including CRT leads to improved survival and quality of life and diminishes the difference in these outcomes between conservative management and heart transplantation within the time-frame studied. Patient selection for heart transplantation requires consideration of these results.

Inclusion of Brefeldin A during dendritic cell isolation allows in vitro detection of cross-presented self-antigens.

The mechanism of cross-presentation enables dendritic cells (DC) to induce immunity against intracellular pathogens and to tolerize autoreactive CD8 T cells. The antigen-presenting cells (APCs) responsible for cross-presentation of self-antigens have been identified as CD8alpha(+) CD11c(+) DC. Isolation of these cells has been notoriously difficult, and the resulting responses of T cell hybridomas were too low to permit further studies. Here, we demonstrate that inclusion of Brefeldin A (BfA), an agent reported to block MHC class I-peptide complex turnover on the cell surface, during DC isolation from transgenic RIP-mOVA mice facilitated activation and proliferation of naïve OVA-specific CD8(+) T cells in vitro. CD8alpha(+) DC were more efficient than CD8alpha(-) CD11c(+). BfA also reversibly preserved expression of costimulatory molecules by DC, as evidenced by their expression of costimulatory markers and by an increased stimulatory capacity of DC matured in vivo by LPS. We conclude that the use of BfA notably improves sensitivity of detection of cross-presented self-antigens.

Cutting edge: TLR ligands are not sufficient to break cross-tolerance to self-antigens.

Cross-presentation of peripheral self-Ags by dendritic cells (DC) can induce deletion of autoreactive CTL by a mechanism termed cross-tolerance. Activation of DC by microbial TLR ligands is thought to result in adaptive immunity. However, activation of tolerogenic DC may cause autoimmunity by stimulating instead of deleting autoreactive CTL. To investigate this scenario, we have monitored the response of autoreactive CTL in specific for the transgenic self Ag, OVA, expressed in pancreatic islets of RIP-mOVA mice injected with ligands of TLR2, 3, 4, and 9. This somewhat enhanced proliferation and cytokine production, and moderately reduced the CTL number able to induce autoimmunity. Nevertheless, physiological CTL numbers were deleted before disease ensued, unless specific CD4 T cell help was provided. In conclusion, DC activation by TLR ligands was insufficient to break peripheral cross-tolerance in the absence of specific CD4 T cell help, and triggered autoimmunity by stimulating the early effector phase of autoreactive CTL only when their precursor frequency was extremely high.

Heat shock protein 60 is released in immune-mediated glomerulonephritis and aggravates disease: in vivo evidence for an immunologic danger signal.

Heat shock proteins (Hsp) are ubiquitous intracellular proteins that can be released in various forms of cellular stress. Some Hsp, such as Hsp60, have been shown to stimulate directly T cell-mediated immune responses in vitro. Here, it is demonstrated that Hsp60 is released from the kidneys and excreted into the urine of mice with nephrotoxic nephritis (NTN), a model of rapidly progressive glomerulonephritis. For examining the functional relevance of Hsp60 release, this protein was injected into mice with subnephritogenic NTN, in which only transient proteinuria and minimal organ damage occur that do not progress to terminal kidney failure. Injection of Hsp60 strikingly aggravated disease, as evidenced by global glomerular necrosis, tubulointerstitial damage, and complete anuria after 10 to 12 d. This effect was mediated neither by endotoxin contaminations of Hsp60 nor by autologous antibodies. It was strictly T cell dependent but not associated with a systemic Th1/Th2 shift. Thus, Hsp60 is an endogenous mediator stimulating immune effector mechanisms that contribute to the progression of NTN. These findings demonstrate in vivo that Hsp60 fulfills criteria of immunologic danger signals and suggest that such signals may be involved in immune-mediated kidney disease.

Identification and functional characterization of dendritic cells in the healthy murine kidney and in experimental glomerulonephritis.

The kidney tubulointerstitium contains numerous bone marrow-derived antigen-presenting cells, which are often referred to as resident tissue macrophages, although several previous studies had demonstrated characteristics of dendritic cells (DC). In this study, we describe a subset of tubulointerstitial cells expressing the DC marker CD11c. A protocol was established to isolate these cells for in vitro analysis. Renal CD11c(+) cells resembled splenic DC, but not peritoneal macrophages, in morphology, lysosomal content, phagocytic activity, microbicidal effector functions, expression of T cell costimulatory molecules, and ability to activate T cells. Nevertheless, many CD11c(+) renal cells expressed low or intermediate levels of F4/80 and CD11b, indicating that both markers are not absolutely specific for macrophages in the kidney. Subpopulations of renal DC could be distinguished based on their expression of MHC class II and costimulatory molecules and may represent different maturation stages. In nephrotoxic glomerulonephritis, increased numbers of CD11c(+) cells showing DC functionality were found in the tubulointerstitium. Focal accumulation was seen within tubulointerstitial mononuclear infiltrates and adjacent to, but not within, inflamed glomeruli. These results are the first to identify and characterize renal CD11c(+) cells as DC and to demonstrate marked changes in experimental glomerulonephritis.

Cure of prediabetic mice by viral infections involves lymphocyte recruitment along an IP-10 gradient.

Viruses can cause but can also prevent autoimmune disease. This dualism has certainly hampered attempts to establish a causal relationship between viral infections and type 1 diabetes (T1D). To develop a better mechanistic understanding of how viruses can influence the development of autoimmune disease, we exposed prediabetic mice to various viral infections. We used the well-established NOD and transgenic RIP-LCMV models of autoimmune diabetes. In both cases, infection with the lymphocytic choriomeningitis virus (LCMV) completely abrogated the diabetic process. Interestingly, such therapeutic viral infections resulted in a rapid recruitment of T lymphocytes from the islet infiltrate to the pancreatic draining lymph node, where increased apoptosis was occurring. In both models this was associated with a selective and extensive expression of the chemokine IP-10 (CXCL10), which predominantly attracts activated T lymphocytes, in the pancreatic draining lymph node, and in RIP-LCMV mice it depended on the viral antigenic load. In RIP-LCMV mice, blockade of TNF-alpha or IFN-gamma in vivo abolished the prevention of T1D. Thus, virally induced proinflammatory cytokines and chemokines can influence the ongoing autoaggressive process beneficially at the preclinical stage, if produced at the correct location, time, and levels.

Atrial fibrillation-induced atrial contractile dysfunction: a tachycardiomyopathy of a different sort.

OBJECTIVE: Although AF-induced atrial contractile dysfunction has significant clinical implications the underlying intracellular mechanisms are poorly understood. METHODS: From the right atrial appendages of 59 consecutive patients undergoing mitral valve surgery (31 in SR, 28 in chronic AF) thin muscle preparations (diameter<0.7 mm) were isolated. Isometric force of contraction was measured in the presence of different concentrations of Ca(2+) and isoprenaline. To assess the function of the sarcoplasmic reticulum, the force-frequency relationship and the post-rest potentiation were studied. The myocardial density of the ryanodine-sensitive calcium release channel (CRC) of the sarcoplasmic reticulum was determined by [3H]ryanodine binding. Myocardial content of SR-Ca(2+)-ATPase (SERCA), phospholamban (Plb), calsequestrin (Cals) and the Na(+)/Ca(2+)-exchanger (NCX) were analyzed by Western blot analysis. Adenylyl cyclase activity was measured with a radiolabeled bioassay using [32P]ATP as a tracer. RESULTS: In 72 muscle preparations of SR patients contractile force was 10.9+/-1.8 mN/mm(2) compared to 3.3+/-0.9 mN/mm(2) (n=48, P<0.01) in AF patients. The positive inotropic effect of isoprenaline was diminished but the stimulatory effect on relaxation and the adenylyl cyclase were not altered in AF patients. The force-frequency relation and the post-rest potentiation were enhanced in atrial myocardium of AF patients. The protein levels of CRC, SERCA, Plb, and Cals were not different between the two groups. In contrast, the Na(+)/Ca(2+)-exchanger was upregulated by 67% in atria of AF patients. CONCLUSIONS: AF-induced atrial contractile dysfunction is not due to beta-adrenergic desensitization or dysfunction of the sarcoplasmic reticulum and thus is based on different cellular mechanisms than a ventricular tachycardia-induced cardiomyopathy. Instead, downregulation or altered function of the L-type Ca(2+)-channel and an increased Ca(2+) extrusion via the Na(+)/Ca(2+)-exchanger seem to be responsible for the depressed contractility in remodeled atria.