Area under the curve analysis of blood pressure reveals increased spontaneous locomotor activity in SPAK knock-in mice: relevance for hypotension induced by SPAK inhibition?

Weak Hypotensive Effect of Chronic Administration of the Dual FAAH/MAGL Inhibitor JZL195 in Spontaneously Hypertensive Rats as Revealed by Area under the Curve Analysis

The enhancement of the endocannabinoid tone might have a beneficial influence on hypertension. Polypharmacology proposes multi-target-directed ligands (MTDLs) as potential therapeutic agents for the treatment of complex diseases. In the present paper, we studied JZL195, a dual inhibitor of the two major endocannabinoid-degrading enzymes, fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL), in spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY). Hemodynamic parameters were assessed in conscious animals via radiotelemetry and tail-cuff methods and then evaluated by the area under the curve (AUC). Single administration of JZL195 induced dose-dependent weak hypotensive and bradycardic responses in SHR but not in WKY. Similarly, its chronic application revealed only a slight hypotensive potential which, however, effectively prevented the progression of hypertension and did not undergo tolerance. In addition, multiple JZL195 administrations slightly decreased heart rate only in WKY and prevented the gradual weight gain in both groups. JZL195 did not affect organ weights, blood glucose level, rectal temperature and plasma oxidative stress markers. In conclusion, chronic dual FAAH/MAGL inhibition prevents the progression of hypertension in SHR without affecting some basal functions of the body. In addition, our study clearly proves the suitability of AUC for the evaluation of weak blood pressure changes.

A systematic review on reporting of refinement measures in mouse ECG telemetry implantation surgery

Telemetric monitoring is used in many scientific fields, such as cardiovascular research, neurology, endocrinology, as well as animal welfare research. Nowadays, implanted electrocardiogram (ECG) radiotelemetry units are the gold standard for monitoring ECG traces, heart rate and heart rate variability in freely moving mice. Telemetry technology can be a valuable tool when studies utilize it adequately, while prioritizing animal welfare. Recently, concerns have been raised in many research fields, including animal research, regarding the reproducibility of research findings, with insufficient reporting being one of the underlying causes.A systematic review was performed by making use of three literature databases, in order to include all publications until 31.12.2019, where the surgical placing of ECG recording telemetry devices in adult mice was involved. Data extracted from the publications included selected items recommended by the ARRIVE guidelines. We focused on aspects related to the refinement of the surgery and experimental conditions that aim to improve animal welfare. In general, the quality of reporting was low in the analyzed 234 publications. Based on our analyses, we assume there has been no improvement in this field's reporting quality since 2010 when the ARRIVE guidelines on reporting were introduced. Additionally, even though expert recommendations on telemetry surgery refinement have been available since many years now, no increase in uptake (or reporting) of these measures prior (e.g., acclimatization), during (e.g., asepsis) or after (e.g., social housing) the surgery could be observed.

Increase in cardioprotective SUR2A does not alter heart rate and heart rate regulation by physical activity and diurnal rhythm

OBJECTIVES

SUR2A is an ABC protein serving as a regulatory subunit of ATP-sensitive (K_ATP) channels. An increase in SUR2A levels is cardioprotective and it is a potential therapeutic strategy against ischaemic heart disease, heart failure and other diseases. However, whether overexpression of this protein has any adverse effects is yet to be fully understood. Here, we examined the heart rate and the heart rate diurnal variation in mice overexpressing SUR2A (SUR2A+) and their littermate controls (WT) using ECG telemetry that was continuously recorded for 14 days (days 8-23 post-radiotransmitter implantation).

METHODS

Using SigmaPlot 14.0 and Microsoft Excel, Area Under the Curve (AUC) for each parameter was calculated and plotted in a graph.

RESULTS

Both WT and SUR2A+ mice were more physically active during nights and there were no significant differences between two phenotypes. Physical activity was associated with increased heart rate in both phenotypes, but there were no differences in heart rate between phenotypes irrespective of physical activity or time of the day. A diurnal heart rate variation was preserved in the SUR2A+ mice. As area under the curve (AUC) analysis has the potential to reveal differences that are invisible with other statistical methods, we compared AUC of heart rate in SUR2A+ and WT mice. This analysis did not yield anything different from traditional analysis.

CONCLUSIONS

We conclude that increased SUR2A levels are not associated with changes in physical activity, heart rate and/or circadian rhythm influence on the heart rate. This lack of adverse effects supports a notion that manipulation with SUR2A levels is a promising cardioprotective strategy.

Regulatory control of the Na-Cl co-transporter NCC and its therapeutic potential for hypertension

Hypertension is the largest risk factor for cardiovascular disease, the leading cause of mortality worldwide. As blood pressure regulation is influenced by multiple physiological systems, hypertension cannot be attributed to a single identifiable etiology. Three decades of research into Mendelian forms of hypertension implicated alterations in the renal tubular sodium handling, particularly the distal convoluted tubule (DCT)-native, thiazide-sensitive Na-Cl cotransporter (NCC). Altered functions of the NCC have shown to have profound effects on blood pressure regulation as illustrated by the over activation and inactivation of the NCC in Gordon's and Gitelman syndromes respectively. Substantial progress has uncovered multiple factors that affect the expression and activity of the NCC. In particular, NCC activity is controlled by phosphorylation/dephosphorylation, and NCC expression is facilitated by glycosylation and negatively regulated by ubiquitination. Studies have even found parvalbumin to be an unexpected regulator of the NCC. In recent years, there have been considerable advances in our understanding of NCC control mechanisms, particularly via the pathway containing the with-no-lysine [K] (WNK) and its downstream target kinases, SPS/Ste20-related proline-alanine-rich kinase (SPAK) and oxidative stress responsive 1 (OSR1), which has led to the discovery of novel inhibitory molecules. This review summarizes the currently reported regulatory mechanisms of the NCC and discusses their potential as therapeutic targets for treating hypertension.

Simultaneous Three-Dimensional Vascular and Tubular Imaging of Whole Mouse Kidneys With X-ray μCT

Concurrent three-dimensional imaging of the renal vascular and tubular systems on the whole-kidney scale with capillary level resolution is labor-intensive and technically difficult. Approaches based on vascular corrosion casting and X-ray micro computed tomography (μCT), for example, suffer from vascular filling artifacts and necessitate imaging with an additional modality to acquire tubules. In this work, we report on a new sample preparation, image acquisition, and quantification protocol for simultaneous vascular and tubular μCT imaging of whole, uncorroded mouse kidneys. The protocol consists of vascular perfusion with the water-soluble, aldehyde-fixable, polymeric X-ray contrast agent XlinCA, followed by laboratory-source μCT imaging and structural analysis using the freely available Fiji/ImageJ software. We achieved consistent filling of the entire capillary bed and staining of the tubules in the cortex and outer medulla. After imaging at isotropic voxel sizes of 3.3 and 4.4 μm, we segmented vascular and tubular systems and quantified luminal volumes, surface areas, diffusion distances, and vessel path lengths. This protocol permits the analysis of vascular and tubular parameters with higher reliability than vascular corrosion casting, less labor than serial sectioning and leaves tissue intact for subsequent histological examination with light and electron microscopy.

Improved adaptation to physical stress in mice overexpressing SUR2A is associated with changes in the pattern of Q-T interval

The purpose of this study was to determine whether increased expression of SUR2A, a regulatory subunit of sarcolemmal ATP-sensitive K⁺ (K_ATP) channels, improves adaptation to physical stress and regulates cardiac electrophysiology in physical stress. All experiments have been done on transgenic mice in which SUR2A expression was controlled by cytomegalovirus immediate-early (CMV) promoter (SUR2A) and their littermate wild-type controls (WT). The levels of mRNA in heart tissue were measured by real-time RT-PCR. Electrocardiogram (ECG) was monitored with telemetry. The physical adaptation to stress was elucidated using treadmill. We have found that SUR2A mice express 8.34 ± 0.20 times more myocardial SUR2A mRNA than WT (n = 8–18). The tolerated workload on exercise stress test was more than twofold higher in SUR2A than in WT (n = 5–7; P = 0.01). The pattern of Q-T interval from the beginning of the exercise test until drop point was as follows in the wild type: (1) increase in Q-T interval, (2) decrease in Q-T interval, (3) steady stage with a further decrease in Q-T interval, and (4) a sharp increase in Q-T interval. The pattern of Q-T interval was different in transgenic mice and the following stages have been observed: (1) increase in Q-T interval, (2) decrease in Q-T interval, and (3) prolonged steady-state stage with a slight decrease in Q-T interval. In SUR2A mice, no stage 4 (a sharp increase in Q-T interval) was observed. Based on the obtained results, we conclude that an increase in the expression of SUR2A improves adaptation to physical stress and physical endurance by increasing the number of sarcolemmal K_ATP channels and, by virtue of their channel activity, improving Ca²⁺ homeostasis in the heart.