Effects of echinocandin preparations on adult rat ventricular cardiomyocytes. Preliminary results of an in vitro study

Caspofungin-Induced Cardiotoxicity in Patients Treating for Candidemia

Echinocandins selectively inhibit fungal cell wall synthesis and, therefore, have few side effects. However, there are reports of hemodynamic and cardiac complications. We conducted this study to investigate the effects of caspofungin both on the noninvasive echocardiographic indices of myocardial function and myocardial injury based on serum high-sensitivity cardiac troponin I (hs-cTnI) levels. This study was conducted on patients treated for candidemia. The hs-cTnI level and echocardiographic parameters were measured before and 1 h after the infusion of the induction dose of caspofungin. Data were compared between central and peripheral venous drug administration routes. Fifteen patients were enrolled in the study. There were no significant differences in the echocardiographic parameters between the baseline and post-treatment period. The mean hs-cTnI level exhibited a significant rise following drug administration (0.24 ± 0.2 ng/mL vs 0.32 ± 0.3 ng/mL; p = 0.006). There was also a significant difference concerning the hs-cTnI level between central and peripheral venous drug administration routes (p = 0.034). Due to differences in the hs-cTnI level, it appears that the administration of caspofungin may be associated with myocardial injury. Our findings also showed a higher possibility of cardiotoxicity via the central venous administration route.

High Throughput Screen Identifies Small Molecule Effectors That Modulate Thin Filament Activation in Cardiac Muscle

Current therapeutic interventions for both heart disease and heart failure are largely insufficient and associated with undesired side effects. Biomedical research has emphasized the role of sarcomeric protein function for the normal performance and energy efficiency of the heart, suggesting that directly targeting the contractile myofilaments themselves using small molecule effectors has therapeutic potential and will likely result in greater drug efficacy and selectivity. In this study, we developed a robust and highly reproducible fluorescence polarization-based high throughput screening (HTS) assay that directly targets the calcium-dependent interaction between cardiac troponin C (cTnC) and the switch region of cardiac troponin I (cTnI_SP), with the aim of identifying small molecule effectors of the cardiac thin filament activation pathway. We screened a commercially available small molecule library and identified several hit compounds with both inhibitory and activating effects. We used a range of biophysical and biochemical methods to characterize hit compounds and identified fingolimod, a sphingosin-1-phosphate receptor modulator, as a new troponin-based small molecule effector. Fingolimod decreased the ATPase activity and calcium sensitivity of demembranated cardiac muscle fibers in a dose-dependent manner, suggesting that the compound acts as a calcium desensitizer. We investigated fingolimod's mechanism of action using a combination of computational studies, biophysical methods, and synthetic chemistry, showing that fingolimod bound to cTnC repels cTnI_SP via mainly electrostatic repulsion of its positively charged tail. These results suggest that fingolimod is a potential new lead compound/scaffold for the development of troponin-directed heart failure therapeutics.

Caspofungin Effects on Electrocardiogram of Mice: An Evaluation of Cardiac Safety

Caspofungin is an echinocandin, exhibiting efficacy against most Candida species invasive infection. Its cardiotoxicity was reported in isolated rat heart and ventricular myocytes, but in vivo and clinical studies are insufficient. Our objective was to evaluate caspofungin in vivo cardiac effects using an efficacious dose against Candida albicans. Female Swiss mice were infected with C. albicans, and treated with caspofungin, 5 or 10 mg/kg, intraperitoneal along 5 days. Survival rate and colony-forming units (CFU) into vital organs were determined. For cardiac effects study, mice were treated with caspofungin 10 mg/kg, and electrocardiogram (ECG) signal was obtained on C. albicans-infected mice, single dose-treated, and uninfected mice treated along 5 days, both groups to measure ECG intervals. Besides, ECG was also obtained by telemetry on uninfected mice to evaluate heart rate variability (HRV) parameters. The MIC for caspofungin on the wild-type C. albicans SC5314 strain was 0.3 μg/ml, indicating the susceptible. Survival rate increased significantly in infected mice treated with caspofungin compared to mice treated with vehicle. None of the survived infected mice presented positive CFU after treatment with 10 mg/kg. C. albicans infection induced prolongation of QRS, QT, and QTc intervals; caspofungin did not alter this effect. Caspofungin induced increase of PR and an additional increase of QRS after 24 h of a single dose in infected mice. No significant alterations occurred in ECG intervals and HRV parameters of uninfected mice, after caspofungin treatment. Caspofungin showed in vivo cardiac relative safety maintaining its antifungal efficacy against C. albicans.

Caspofungin induces the release of Ca2+ ions from internal stores by activating ryanodine receptor-dependent pathways in human tracheal epithelial cells

The antimycotic drug caspofungin is known to alter the cell function of cardiomyocytes and the cilia-bearing cells of the tracheal epithelium. The objective of this study was to investigate the homeostasis of intracellular Ca²⁺ concentration ([Ca²⁺]_i) after exposure to caspofungin in isolated human tracheal epithelial cells. The [Ca²⁺]_i was measured using the ratiometric fluoroprobe FURA-2 AM. We recorded two groups of epithelial cells with distinct responses to caspofungin exposure, which demonstrated either a rapid transient rise in [Ca²⁺]_i or a sustained elevation of [Ca²⁺]_i. Both patterns of Ca²⁺ kinetics were still observed when an influx of transmembraneous Ca²⁺ ions was pharmacologically inhibited. Furthermore, in extracellular buffer solutions without Ca²⁺ ions, caspofungin exposure still evoked this characteristic rise in [Ca²⁺]_i. To shed light on the origin of the Ca²⁺ ions responsible for the elevation in [Ca²⁺]_i we investigated the possible intracellular storage of Ca²⁺ ions. The depletion of mitochondrial Ca²⁺ stores using 25 µM 2,4-dinitrophenol (DNP) did not prevent the caspofungin-induced rise in [Ca²⁺]_i, which was rapid and transient. However, the application of caffeine (30 mM) to discharge Ca²⁺ ions that were presumably stored in the endoplasmic reticulum (ER) prior to caspofungin exposure completely inhibited the caspofungin-induced changes in [Ca²⁺]_i levels. When the ER-bound IP₃ receptors were blocked by 2-APB (40 µM), we observed a delayed transient rise in [Ca²⁺]_i as a response to the caspofungin. Inhibition of the ryanodine receptors (RyR) using 40 µM ryanodine completely prevented the caspofungin-induced elevation of [Ca²⁺]_i. In summary, caspofungin has been shown to trigger an increase in [Ca²⁺]_i independent from extracellular Ca²⁺ ions by liberating the Ca²⁺ ions stored in the ER, mainly via a RyR pathway.

Caspofungin Modulates Ryanodine Receptor-Mediated Calcium Release in Human Cardiac Myocytes

Recent studies showed that critically ill patients might be at risk for hemodynamic impairment during caspofungin (CAS) therapy. The aim of our present study was to examine the mechanisms behind CAS-induced cardiac alterations. We revealed a dose-dependent increase in intracellular Ca²⁺ concentration ([Ca²⁺]_i) after CAS treatment. Ca²⁺ ions were found to be released from intracellular caffeine-sensitive stores, most probably via the activation of ryanodine receptors.

[Strategies for antifungal treatment failure in intensive care units]

Recent epidemiologic studies reveal both an increasing incidence and an escalation in resistance of invasive fungal infections in intensive care units. Primary therapy fails in 70 % of cases, depending on the underlying pathogens and diseases. The purpose of this review is to raise awareness for the topic of antifungal therapy failure, describe the clinical conditions in which it occurs, and suggest a possible algorithm for handling the situation of suspected primary therapy failure.

Cardiac Effects of Echinocandins in Endotoxemic Rats

Echinocandins are known as effective and safe agents for the prophylaxis and treatment of different cohorts of patients with fungal infections. Recent studies revealed that certain pharmacokinetics of echinocandin antifungals might impact clinical efficacy and safety in special patient populations. The aim of our study was to evaluate echinocandin-induced aggravation of cardiac impairment in septic shock. Using an in vivo endotoxemic shock model in rats, we assessed hemodynamic parameters and time to hemodynamic failure (THF) after additional central-venous application of anidulafungin (2.5 mg/kg of body weight [BW]), caspofungin (0.875 mg/kg BW), micafungin (3 mg/kg BW), and control (0.9% sodium chloride). In addition, echinocandin-induced cytotoxicity was evaluated in isolated rat cardiac myocytes. THF of the animals in the caspofungin group (n = 7) was significantly reduced compared to that in the control (n = 6) (136 min versus 180 min; P = 0.0209). The anidulafungin group (n = 7) also showed a trend of reduced THF (136 min versus 180 min; log-rank test P = 0.0578). Animals in the micafungin group (n = 7) did not show significant differences in THF compared to those in the control. Control group animals and also micafungin group animals did not show altered cardiac output (CO) during our experiments. In contrast, administration of anidulafungin or caspofungin induced a decrease in CO. We also revealed a dose-dependent increase of cytotoxicity in anidulafungin- and caspofungin-treated cardiac myocytes. Treatment with micafungin did not cause significantly increased cytotoxicity. Further studies are needed to explore the underlying mechanism.

Cardiac effects of echinocandins after central venous administration in adult rats

Echinocandins have become the agents of choice for early and specific antifungal treatment in critically ill patients. In vitro studies and clinical case reports revealed a possible impact of echinocandin treatment on cardiac function. The aim of our study was to evaluate echinocandin-induced cardiac failure. Using an in vivo rat model, we assessed hemodynamic parameters and time to hemodynamic failure after central venous application (vena jugularis interna) of anidulafungin (low-dose group, 2.5 mg/kg body weight [BW]; high-dose group, 25 mg/kg BW), caspofungin (low-dose group, 0.875 mg/kg BW; high-dose group, 8.75 mg/kg BW), micafungin (low-dose group, 3 mg/kg BW; high-dose group, 30 mg/kg BW), and placebo (0.9% sodium chloride). Left ventricular heart tissue was collected to determine mitochondrial enzyme activity via spectrophotometric measurements. mRNA expression of transcriptional regulators and primary mitochondrial transcripts, mitochondrial DNA (mtDNA) content, and citrate synthase activity were also explored. Animals receiving high-dose anidulafungin or caspofungin showed an immediate decrease in hemodynamic function. All of the subjects in these groups died during the observation period. Every animal in the untreated control group survived (P < 0.001). Hemodynamic failure was not noticed in the anidulafungin and caspofungin low-dose groups. Micafungin had no impact on cardiac function. In analyzing mitochondrial enzyme activity and mitochondrial transcripts, we found no association between echinocandin administration and the risk for hemodynamic failure. Further experimental studies are needed to elucidate the underlying mechanisms involved in cardiotoxic echinocandin effects. In addition, randomized controlled clinical trials are needed to explore the clinical impact of echinocandin treatment in critically ill patients.