An analysis of DPV and DIVE registry patients with chronic kidney disease according to the finerenone phase III clinical trial selection criteria.

BACKGROUND: The FIDELIO-DKD and FIGARO-DKD randomized clinical trials (RCTs) showed finerenone, a novel non-steroidal mineralocorticoid receptor antagonist (MRA), reduced the risk of renal and cardiovascular events in patients with type 2 diabetes mellitus (T2DM) and chronic kidney disease (CKD). Using RCT inclusion and exclusion criteria, we analyzed the RCT coverage for patients with T2DM and CKD in routine clinical practice in Germany. METHODS: German patients from the DPV/DIVE registries who were ≥ 18 years, had T2DM and CKD (an estimated glomerular filtration rate [eGFR] < 60 mL/min/1.73 m2 OR eGFR ≥ 60 mL/min/1.73m2 and albuminuria [≥ 30 mg/g]) were included. RCT inclusion and exclusion criteria were then applied, and the characteristics of the two populations compared. RESULTS: Overall, 65,168 patients with T2DM and CKD were identified from DPV/DIVE. Key findings were (1) Registry patients with CKD were older, less often male, and had a lower eGFR, but more were normoalbuminuric vs the RCTs. Cardiovascular disease burden was higher in the RCTs; diabetic neuropathy, lipid metabolism disorders, and peripheral arterial disease were more frequent in the registry. CKD-specific drugs (e.g., angiotensin-converting enzyme inhibitors [ACEi] and angiotensin receptor blocker [ARBs]) were used less often in clinical practice; (2) Due to the RCT's albuminuric G1/2 to G4 CKD focus, they did not cover 28,147 (43.2%) normoalbuminuric registry patients, 4,519 (6.9%) albuminuric patients with eGFR < 25, and 6,565 (10.1%) patients with microalbuminuria but normal GFR (≥ 90 ml/min); 3) As RCTs required baseline ACEi or ARB treatment, the number of comparable registry patients was reduced to 28,359. Of these, only 12,322 (43.5%) registry patients fulfilled all trial inclusion and exclusion criteria. Registry patients that would have been eligible for the RCTs were more often male, had higher eGFR values, higher rates of albuminuria, more received metformin, and more SGLT-2 inhibitors than patients that would not be eligible. CONCLUSIONS: Certain patient subgroups, especially non-albuminuric CKD-patients, were not included in the RCTs. Although recommended by guidelines, there was an undertreatment of CKD-patients with renin-angiotensin system (RAS) blockers. Further research into patients with normoalbuminuric CKD and a wider prescription of RAS blocking agents for CKD patients in clinical practice appears warranted.

Distant positioning of proteasomal proteolysis relative to actively transcribed genes.

While it is widely acknowledged that the ubiquitin-proteasome system plays an important role in transcription, little is known concerning the mechanistic basis, in particular the spatial organization of proteasome-dependent proteolysis at the transcription site. Here, we show that proteasomal activity and tetraubiquitinated proteins concentrate to nucleoplasmic microenvironments in the euchromatin. Such proteolytic domains are immobile and distinctly positioned in relation to transcriptional processes. Analysis of gene arrays and early genes in Caenorhabditis elegans embryos reveals that proteasomes and proteasomal activity are distantly located relative to transcriptionally active genes. In contrast, transcriptional inhibition generally induces local overlap of proteolytic microdomains with components of the transcription machinery and degradation of RNA polymerase II. The results establish that spatial organization of proteasomal activity differs with respect to distinct phases of the transcription cycle in at least some genes, and thus might contribute to the plasticity of gene expression in response to environmental stimuli.

Activated STAT1 transcription factors conduct distinct saltatory movements in the cell nucleus.

The activation of STAT transcription factors is a critical determinant of their subcellular distribution and their ability to regulate gene expression. Yet, it is not known how activation affects the behavior of individual STAT molecules in the cytoplasm and nucleus. To investigate this issue, we injected fluorescently labeled STAT1 in living HeLa cells and traced them by single-molecule microscopy. We determined that STAT1 moved stochastically in the cytoplasm and nucleus with very short residence times (<0.03 s) before activation. Upon activation, STAT1 mobility in the cytoplasm decreased ∼2.5-fold, indicating reduced movement of STAT1/importinα/ß complexes to the nucleus. In the nucleus, activated STAT1 displayed a distinct saltatory mobility, with residence times of up to 5 s and intermittent diffusive motion. In this manner, activated STAT1 factors can occupy their putative chromatin target sites within ∼2 s. These results provide a better understanding of the timescales on which cellular signaling and regulated gene transcription operate at the single-molecule level.

Discontinuous movement of mRNP particles in nucleoplasmic regions devoid of chromatin.

Messenger ribonucleoprotein particles (mRNPs) move randomly within nucleoplasm before they exit from the nucleus. To further understand mRNP trafficking, we have studied the intranuclear movement of a specific mRNP, the BR2 mRNP, in salivary gland cells in Chironomus tentans. Their polytene nuclei harbor giant chromosomes separated by vast regions of nucleoplasm, which allows us to study mRNP mobility without interference of chromatin. The particles were fluorescently labeled with microinjected oligonucleotides (DNA or RNA) complementary to BR2 mRNA or with the RNA-binding protein hrp36, the C. tentans homologue of hnRNP A1. Using high-speed laser microscopy, we followed the intranuclear trajectories of single mRNPs and characterized their motion within the nucleoplasm. The Balbiani ring (BR) mRNPs moved randomly, but unexpectedly, in a discontinuous manner. When mobile, they diffused with a diffusion coefficient corresponding to their size. Between mobile phases, the mRNPs were slowed down 10- to 250-fold but were never completely immobile. Earlier electron microscopy work has indicated that BR particles can attach to thin nonchromatin fibers, which are sometimes connected to discrete fibrogranular clusters. We propose that the observed discontinuous movement reflects transient interactions between freely diffusing BR particles and these submicroscopic structures.

Balbiani ring mRNPs diffuse through and bind to clusters of large intranuclear molecular structures.

A detailed conception of intranuclear messenger ribonucleoprotein particle (mRNP) dynamics is required for the understanding of mRNP processing and gene expression outcome. We used complementary state-of-the-art fluorescence techniques to quantify native mRNP mobility at the single particle level in living salivary gland cell nuclei. Molecular beacons and fluorescent oligonucleotides were used to specifically label BR2.1 mRNPs by an in vivo fluorescence in situ hybridization approach. We characterized two major mobility components of the BR2.1 mRNPs. These components with diffusion coefficients of 0.3 ± 0.02 µm²/s and 0.73 ± 0.03 µm²/s were observed independently of the staining method and measurement technique used. The mobility analysis of inert tracer molecules revealed that the gland cell nuclei contain large molecular nonchromatin structures, which hinder the mobility of large molecules and particles. The mRNPs are not only hindered by these mobility barriers, but in addition also interact presumably with these structures, what further reduces their mobility and effectively leads to the occurrence of the two diffusion coefficients. In addition, we provide evidence that the remarkably high mobility of the large, 50 nm-sized BR2.1 mRNPs was due to the absence of retarding chromatin.

High-contrast single-particle tracking by selective focal plane illumination microscopy.

Wide-field single molecule microscopy is a versatile tool for analyzing dynamics and molecular interactions in biological systems. In extended three-dimensional systems, however, the method suffers from intrinsic out-of-focus fluorescence. We constructed a high-resolution selective plane illumination microscope (SPIM) to efficiently solve this problem. The instrument is an optical sectioning microscope featuring the high speed and high sensitivity of a video microscope. We present theoretical calculations and quantitative measurements of the illumination light sheet thickness yielding 1.7 microm (FWHM) at 543 nm, 2.0 microm at 633 nm, and a FWHM of the axial point spread function of 1.13 microm. A direct comparison of selective plane and epi-illumination of model samples with intrinsic background fluorescence illustrated the clear advantage of SPIM for such samples. Single fluorescent quantum dots in aqueous solution are readily visualized and tracked proving the suitability of our setup for the study of fast and dynamic processes in spatially extended biological specimens.

Inverse response of leukocyte heat shock proteins and DNA damage to exercise and heat.

Elevated ambient temperature may exert an additional impact on the exercise-induced expression of heat shock proteins (HSP) and DNA damage in leukocytes. The protective functions of HSP include antioxidative and antiapoptotic effects and may prevent damage to DNA. Twelve athletes completed a continuous run (75% VO2max) on the treadmill, six at 28 degrees C and six at 18 degrees C room temperature. Leukocyte expression of HSP27 and inducible HSP70 was analyzed on mRNA- (RT-PCR) and protein-level (flow cytometry), while DNA damage was quantified by the comet assay. High ambient temperature induced an additional accumulation of HSP-mRNA and -protein in leukocytes compared with the exercise-induced expression at 18 degrees C. HSP27 showed a special heat sensitivity. Surprisingly, the increase of DNA damage was less pronounced after exercise at 28 degrees C compared to 18 degrees C although heat shock in vitro clearly induced DNA damage. The inverse relation between HSP and DNA damage may indicate functions of HSP which protect against exercise-induced DNA-damage in terms of thermotolerance or apoptosis.

Light sheet microscopy for single molecule tracking in living tissue.

Single molecule observation in cells and tissue allows the analysis of physiological processes with molecular detail, but it still represents a major methodological challenge. Here we introduce a microscopic technique that combines light sheet optical sectioning microscopy and ultra sensitive high-speed imaging. By this approach it is possible to observe single fluorescent biomolecules in solution, living cells and even tissue with an unprecedented speed and signal-to-noise ratio deep within the sample. Thereby we could directly observe and track small and large tracer molecules in aqueous solution. Furthermore, we demonstrated the feasibility to visualize the dynamics of single tracer molecules and native messenger ribonucleoprotein particles (mRNPs) in salivary gland cell nuclei of Chironomus tentans larvae up to 200 microm within the specimen with an excellent signal quality. Thus single molecule light sheet based fluorescence microscopy allows analyzing molecular diffusion and interactions in complex biological systems.