Telemetric long-term assessment of autonomic function in experimental heart failure.

Despite medical advances in the treatment of heart failure (HF), mortality remains high. It has been shown that alterations of the autonomic-nervous-system (ANS) are associated with HF progression and increased mortality. Preclinical models are required to evaluate the effectiveness of novel treatments modulating the autonomic imbalance. However, there are neither standard models nor diagnostic methods established to measure sympathetic and parasympathetic outflow continuously. Digital technologies might be a reliable tool for continuous assessment of autonomic function within experimental HF models. Telemetry devices and pacemakers were implanted in beagle dogs (n = 6). HF was induced by ventricular pacing. Cardiac hemodynamics, plasma catecholamines and parameter describing the ANS ((heart rate variability (HRV), deceleration capacity (DC), and baroreflex sensitivity (BRS)) were continuously measured at baseline, during HF conditions and during recovery phase. The pacing regime led to the expected depression in cardiac hemodynamics. Telemetric assessment of the ANS function showed a significant decrease in Total power, DC, and Heart rate recovery, whereas BRS was not significantly affected. In contrast, plasma catecholamines, revealing sympathetic activity, showed only a significant increase in the recovery phase. A precise diagnostic of the ANS in the context of HF is becoming increasingly important in experimental models. Up to now, these models have shown many limitations. Here we present the continuous assessment of the autonomic function in the progression of HF. We could demonstrate the advantage of highly resolved ANS measurement by HR and BP derived parameters due to early detection of an autonomic imbalance in the progression of HF.

Rational design of highly stabilized and selective adrenomedullin analogs.

The peptide hormone adrenomedullin (ADM) consists of 52 amino acids with a disulfide bond and an amidated C-terminus. Due to the vasodilatory and cardioprotective effects, the agonistic activity of the peptide on the adrenomedullin 1 receptor (AM1 R) is of high pharmacological interest. However, the wild-type peptide shows low metabolic stability leading to rapid degradation in the cardiovascular system. Previous work by our group has identified proteolytic cleavage sites and demonstrated stabilization of ADM by lipidation, cyclization, and N-methylation. Nevertheless, these ADM analogs showed reduced activity and subtype selectivity toward the closely related calcitonin gene-related peptide receptor (CGRPR). Here, we report on the rational development of ADM derivatives with increased proteolytic stability and high receptor selectivity. Stabilizing motifs, including lactamization and lipidation, were evaluated regarding AM1 R and CGRPR activation. Furthermore, the central DKDK motif of the peptide was replaced by oligoethylene glycol linkers. The modified peptides were synthesized by Fmoc/t-Bu solid-phase peptide synthesis and receptor activation of AM1 R and CGRPR was measured by cAMP reporter gene assay. Peptide stability was tested in human blood plasma and porcine liver homogenate and analyzed by RP-HPLC and MALDI-ToF mass spectrometry. Combination of the favorable lactam, lipidation, ethylene glycol linker, and previously described disulfide mimetic resulted in highly stabilized analogs with a plasma half-life of more than 144 h. The compounds display excellent AM1 R activity and wild-type-like selectivity toward CGRPR. Additionally, dose-dependent vasodilatory effects of the ADM derivatives lasted for several hours in rodents. Thus, we successfully developed an ADM analog with long-term in vivo activity.

Cellular interaction of a layer-by-layer based drug delivery system depending on material properties and cell types.

BACKGROUND: Drug delivery systems (DDS) and their interaction with cells are a controversial topic in the development of therapeutic concepts and approaches. On one hand, DDS are very useful for protected and targeted transport of defined dosages of active agents. On the other hand, their physicochemical properties such as material, size, shape, charge, or stiffness have a huge impact on cellular uptake and intracellular processing. Additionally, even identical DDS can undergo a completely diverse interaction with different cell types. However, quite often in in vitro DDS/cell interaction experiments, those aspects are not considered and DDS and cells are randomly chosen. METHODS AND RESULTS: Hence, our investigations provide an insight into layer-by-layer designed microcarriers with modifications of only some of the most important parameters (surface charge, stiffness, and applied microcarrier/cell ratio) and their influence on cellular uptake and viability. We also considered the interaction of these differently equipped DDS with several cell types and investigated professional phagocytes (neutrophil granulocytes; macrophages) as well as non-professional phagocytes (epithelial cells) under comparable conditions. We found that even small modifications such as layer-by-layer (LbL)-microcarriers with positive or negative surface charge, or LbL-microcarriers with solid core or as hollow capsules but equipped with the same surface properties, show significant differences in interaction and viability, and several cell types react very differently to the offered DDS. CONCLUSION: As a consequence, the properties of the DDS have to be carefully chosen with respect to the addressed cell type with the aim to efficiently transport a desired agent.