The Dysfunction of Ca2+ Channels in Hereditary and Chronic Human Heart Diseases and Experimental Animal Models

Chronic heart diseases, such as coronary heart disease, heart failure, secondary arterial hypertension, and dilated and hypertrophic cardiomyopathies, are widespread and have a fairly high incidence of mortality and disability. Most of these diseases are characterized by cardiac arrhythmias, conduction, and contractility disorders. Additionally, interruption of the electrical activity of the heart, the appearance of extensive ectopic foci, and heart failure are all symptoms of a number of severe hereditary diseases. The molecular mechanisms leading to the development of heart diseases are associated with impaired permeability and excitability of cell membranes and are mainly caused by the dysfunction of cardiac Ca2+ channels. Over the past 50 years, more than 100 varieties of ion channels have been found in the cardiovascular cells. The relationship between the activity of these channels and cardiac pathology, as well as the general cellular biological function, has been intensively studied on several cell types and experimental animal models in vivo and in situ. In this review, I discuss the origin of genetic Ca2+ channelopathies of L- and T-type voltage-gated calcium channels in humans and the role of the non-genetic dysfunctions of Ca2+ channels of various types: L-, R-, and T-type voltage-gated calcium channels, RyR2, including Ca2+ permeable nonselective cation hyperpolarization-activated cyclic nucleotide-gated (HCN), and transient receptor potential (TRP) channels, in the development of cardiac pathology in humans, as well as various aspects of promising experimental studies of the dysfunctions of these channels performed on animal models or in vitro.

Genetic ablation of Toll-like Receptor 4 seems to activate the apoptosis pathway in the skeletal muscle of mice after acute physical exercise

Many conditions, such as inflammation and physical exercise, can induce endoplasmic reticulum (ER) stress. Toll-like Receptor 4 (TLR4) can trigger inflammation and ER stress events. However, there are still no data in the literature regarding the role of TLR4 in ER stress during exercise in skeletal muscle. Therefore, the current investigation aimed to verify the responses of ER stress markers in wild-type (WT) and Tlr4 global knockout (KO) mice after acute and chronic physical exercise protocols. Eight-week-old male WT and KO mice were submitted to acute (moderate or high intensity) and chronic (4-week protocol) treadmill exercises. Under basal conditions, KO mice showed lower performance in the rotarod test. Acute high-intensity exercise increased eIF2α protein in the WT group. After the acute high-intensity exercise, there was an increase in Casp3 and Ddit3 mRNA for the KO mice. Acute moderate exercise increased the cleaved Caspase-3/Caspase-3 in the KO group. In response to chronic exercise, the KO group showed no improvement in any performance evaluation. The 4-week chronic protocol did not generate changes in ATF6, CHOP, p-IRE1α, p-eIF2α/eIF2α, and cleaved Caspase-3/Caspase-3 ratio but reduced BiP protein compared with the KO-Sedentary group. These results demonstrate the global deletion of Tlr4 seems to have the same effects on UPR markers of WT animals after acute and chronic exercise protocols but decreased performance. The cleaved Caspase-3/Caspase-3 ratio may be activated by another pathway other than ER stress in Tlr4 KO animals.

Hyperuricemia during Pregnancy Leads to a Preeclampsia-Like Phenotype in Mice

Hyperuricemia is a common feature in pregnancies compromised by pre-eclampsia, a pregnancy disease characterized by hypertension and proteinuria. The role of uric acid in the pathogenesis of pre-eclampsia remains largely unclear. The aim of this study was to investigate the effect of elevated uric acid serum levels during pregnancy on maternal blood pressure and neonatal outcome using two different murine knockout models. Non-pregnant liver-specific GLUT9 knockout (LG9KO) mice showed elevated uric acid serum concentrations but no hypertensive blood pressure levels. During pregnancy, however, blood pressure levels of these animals increased in the second and third trimester, and circadian blood pressure dipping was severely altered when compared to non-pregnant LG9KO mice. The impact of hyperuricemia on fetal development was investigated using a systemic GLUT9 knockout (G9KO) mouse model. Fetal hyperuricemia caused distinctive renal tissue injuries and, subsequently an impaired neonatal growth pattern. These findings provide strong evidence that hyperuricemia plays a major role in the pathogenesis of hypertensive pregnancy disorders such as pre-eclampsia. These novel insights may enable the development of preventive and therapeutic strategies for hyperuricemia-related diseases.

Specific ablation of Hippo signalling component Yap1 in retinal progenitors and Müller cells results in late onset retinal degeneration

Yes-associated protein (YAP) is a major component of the Hippo pathway involved in development, growth, repair and homeostasis. Nonsense YAP1 mutations in humans result in autosomal dominant coloboma. Here, we generated a conditional knockout mouse model in which Yap1 was specifically deleted in embryonic retinal progenitor cells (RPCs) and in mature Müller cells using a Chx10-Cre driver. Our data demonstrated that the conditional ablation of Yap1 in embryonic RPCs does not prevent normal retinal development and caused no gross changes in retinal structure during embryonic and early postnatal life. Nevertheless, Yap1 deficient in retinal Müller cells in adult mice leads to impaired visual responses and extensive late-onset retinal degeneration, characterized by reduced cell number in all retinal layers. Immunofluorescence data further revealed the degeneration and death of rod and cone photoreceptors, bipolar cells, horizontal cells, amacrine cells and ganglion cells to varying degrees in aged knockout mice. Moreover, alteration of glial homeostasis and reactive gliosis were also observed. Finally, cell proliferation and TUNEL assay revealed that the broad retinal degeneration is mainly caused by enhanced apoptosis in late period. Together, this work uncovers that YAP is essential for the normal vision and retinal maintenance, highlighting the crucial role of YAP in retinal function and homeostasis.

NRF2-Dependent Placental Effects Vary by Sex and Dose following Gestational Exposure to Ultrafine Particles

Exposure to ultrafine particles (UFPs, PM0.1) during pregnancy triggers placental oxidative stress and inflammation, similar to fine PM (PM2.5). The Nrf2 gene encodes a redox-sensitive transcription factor that is a major regulator of antioxidant and anti-inflammatory responses. Disruption of NRF2 is known to substantially enhance PM2.5-driven oxidant and inflammatory responses; however, specific responses to UFP exposure, especially during critical windows of susceptibility such as pregnancy, are not fully characterized; To investigate the role of NRF2 in regulating maternal antioxidant defenses and placental responses to UFP exposure, wildtype (WT) and Nrf2-/- pregnant mice were exposed to either low dose (LD, 100 µg/m3) or high dose (HD, 500 µg/m3) UFP mixture or filtered air (FA, control) throughout gestation; Nrf2-/- HD-exposed female offspring exhibited significantly reduced fetal and placental weights. Placental morphology changes appeared most pronounced in Nrf2-/- LD-exposed offspring of both sexes. Glutathione (GSH) redox analysis revealed significant increases in the GSH/GSSG ratio (reduced/oxidized) in WT female placental tissue exposed to HD in comparison with Nrf2-/- HD-exposed mice. The expression of inflammatory cytokine genes (Il1β, Tnfα) was significantly increased in Nrf2-/- placentas from male and female offspring across all exposure groups. Genes related to bile acid metabolism and transport were differentially altered in Nrf2-/- mice across sex and exposure groups. Notably, the group with the most marked phenotypic effects (Nrf2-/- HD-exposed females) corresponded to significantly higher placental Apoa1 and Apob expression suggesting a link between placental lipid transport and NRF2 in response to high dose UFP exposure; Disruption of NRF2 exacerbates adverse developmental outcomes in response to high dose UFP exposure in female offspring. Morphological effects in placenta from male and female offspring exposed to low dose UFPs also signify the importance of NRF2 in maternal-fetal response to UFPs.

NRF2 Protects against Altered Pulmonary T Cell Differentiation in Neonates Following In Utero Ultrafine Particulate Matter Exposure

Early life exposure to particulate matter (PM) air pollution negatively impacts neonatal health. The underlying mechanisms following prenatal exposure, particularly to ultrafine particles (UFP, diameter ≤ 0.1 μm), are not fully understood; To evaluate the role of Nrf2 in response to in utero UFP exposure, we exposed time-mated Nrf2-deficient (Nrf2-/-) or wildtype (WT) mice to filtered air (FA) or 100 μg/m3 ultrafine PM daily throughout pregnancy. Offspring were evaluated for pulmonary immunophenotypes and pulmonary/systemic oxidative stress on postnatal day 5, a timepoint at which we previously demonstrated viral respiratory infection susceptibility; Nrf2-/- offspring exposed to FA had significantly lower average body weights compared to FA-exposed WT pups. Moreover, PM-exposed Nrf2-/- offspring weighed significantly less than PM-exposed WT pups. Notably, PM-exposed Nrf2-/- offspring showed a decreased pulmonary Th1/Th2 ratio, indicating a Th2 bias. Th17 cells were increased in FA-exposed Nrf2-/- neonates yet decreased in PM-exposed Nrf2-/- neonates. Analysis of oxidative stress-related genes in lung and oxidative stress biomarkers in liver tissues did not vary significantly across exposure groups or genotypes. Collectively, these findings indicate that the lack of Nrf2 causes growth inhibitory effects in general and in response to gestational UFP exposure. Prenatal UFP exposure skews CD4+ T lymphocyte differentiation toward Th2 in neonates lacking Nrf2, signifying its importance in maternal exposure and infant immune responses.

Urinary protein analysis in mice lacking major urinary proteins

Mouse urine contains major urinary proteins (MUPs) that are not found in human urine. Therefore, even healthy mice exhibit proteinuria, unlike healthy humans, making it challenging to use mice as models for human diseases. It was also unknown whether dipsticks for urinalysis could measure protein concentrations precisely in urine containing MUPs. To resolve these problems, we produced MUP-knockout (Mup-KO) mice by removing the Mup gene cluster using Cas9 proteins and two guide RNAs and characterized the urinary proteins in these mice. We measured the urinary protein concentrations in Mup-KO and wild-type mice using a protein quantitation kit and dipsticks. We also examined the urinary protein composition using SDS-PAGE and two-dimensional electrophoresis (2DE). The urinary protein concentration was significantly lower (P<0.001) in Mup-KO mice (17.9 ± 1.8 mg/dl, mean ± SD, n=3) than in wild-type mice (73.7 ± 8.2 mg/dl, n=3). This difference was not reflected in the dipstick values, perhaps due to the low sensitivity to MUPs. This suggests that dipsticks have limited ability to measure changes in MUPs with precision. SDS-PAGE and 2DE confirmed that Mup-KO mice, like humans, had no MUPs in their urine, whereas wild-type mice had abundant MUPs in their urine. The absence of the masking effect of MUPs in 2DE would enable clear comparisons of urinary proteins, especially low-molecular-weight proteins. Thus, Mup-KO mice may provide a useful model for human urinalysis.

CRISPR/Cas9-mediated genome-edited mice reveal 10 testis-enriched genes are dispensable for male fecundity

As the world population continues to increase to unsustainable levels, the importance of birth control and the development of new contraceptives are emerging. To date, male contraceptive options have been lagging behind those available to women, and those few options available are not satisfactory to everyone. To solve this problem, we have been searching for new candidate target proteins for non-hormonal contraceptives. Testis-specific proteins are appealing targets for male contraceptives because they are more likely to be involved in male reproduction and their targeting by small molecules is predicted to have no on-target harmful effects on other organs. Using in silico analysis, we identified Erich2, Glt6d1, Prss58, Slfnl1, Sppl2c, Stpg3, Tex33, and Tex36 as testis-abundant genes in both mouse and human. The genes, 4930402F06Rik and 4930568D16Rik, are testis-abundant paralogs of Glt6d1 that we also discovered in mice but not in human, and were also included in our studies to eliminate the potential compensation. We generated knockout (KO) mouse lines of all listed genes using the CRISPR/Cas9 system. Analysis of all of the individual KO mouse lines as well as Glt6d1/4930402F06Rik/4930568D16Rik TKO mouse lines revealed that they are male fertile with no observable defects in reproductive organs, suggesting that these 10 genes are not required for male fertility nor play redundant roles in the case of the 3 Glt6D1 paralogs. Further studies are needed to uncover protein function(s), but in vivo functional screening using the CRISPR/Cas9 system is a fast and accurate way to find genes essential for male fertility, which may apply to studies of genes expressed elsewhere. In this study, although we could not find any potential protein targets for non-hormonal male contraceptives, our findings help to streamline efforts to find and focus on only the essential genes.

Prenatal cocaine exposure disrupts the dopaminergic system and its postnatal responses to cocaine

Impaired attention is the hallmark consequence of prenatal cocaine exposure (PCE), affecting brain development, learning, memory and social adaptation starting at an early age. To date, little is known about the brain structures and neurochemical processes involved in this effect. Through focusing on the visual system and employing zebrafish as a model, we show that PCE reduces expression of dopamine receptor Drd1, with levels reduced in the optic tectum and other brain regions, but not the telencephalon. Organism-wide, PCE results in a 1.7-fold reduction in the expression of the dopamine transporter (dat), at baseline. Acute cocaine administration leads to a 2-fold reduction in dat in drug-naive larvae but not PCE fish. PCE sensitizes animals to an anxiogenic-like behavioral effect of acute cocaine, bottom-dwelling, while loss of DAT due to genetic knockout (DATKO) leads to bottom-dwelling behavior at baseline. Neuronal calcium responses to visual stimuli in both PCE and DATKO fish show tolerance to acute cocaine in the principal regions of visual attention, the telencephalon and optic tectum. The zebrafish model can provide a sensitive assay by which to elucidate the molecular mechanisms and brain region-specific consequences of PCE, and facilitate the search for effective therapeutic solutions.

Knockout of Abi3bp in mice does not affect their olfactory function, mental state and NNK-induced lung tumorigenesis

Abi3bp was originally discovered as Abi3-Src homology 3 (SH3) binding protein and has been proved to have a broad expression profile in adult tissues. Although previous studies have indicated that Abi3bp may be associated with cancer suppression, cell senescence, dendritic refinement and mental disorder, most conclusions achieved were based on in vitro model or genome-wide association study. In this work, we constructed an Abi3bp-deficient mouse model and observed phenotypic changes. The generated Abi3bp-knockout mice are viable and fertile, develop normally and exhibit no significant differences in anxiety or depression-like behaviors, olfactory function and tumor incidence. These data suggest that the function of Abi3bp in in vitro models does not translate to a similar role in the intact animal. Its depletion may be compensated by other genes, which needs to be addressed in future studies.

Ficolins Promote Fungal Clearance in vivo and Modulate the Inflammatory Cytokine Response in Host Defense against Aspergillus fumigatus

Aspergillus fumigatus is an opportunistic fungal pathogen that causes severe invasive infections in immunocompromised patients. Innate immunity plays a major role in protection against A. fumigatus. The ficolins are a family of soluble pattern recognition receptors that are capable of activating the lectin pathway of complement. Previous in vitro studies reported that ficolins bind to A. fumigatus, but their part in host defense against fungal infections in vivo is unknown. In this study, we used ficolin-deficient mice to investigate the role of ficolins during lung infection with A. fumigatus. Ficolin knockout mice showed significantly higher fungal loads in the lungs 24 h postinfection compared to wild-type mice. The delayed clearance of A. fumigatus in ficolin knockout mice could not be attributed to a compromised recruitment of inflammatory cells. However, it was revealed that ficolin knockout mice exhibited a decreased production of proinflammatory cytokines in the lungs compared to wild-type mice following A. fumigatus infection. The impaired clearance and cytokine production in ficolin knockout mice was independent of complement, as shown by equivalent levels of A. fumigatus-mediated complement activation in ficolin knockout mice and wild-type mice. In conclusion, this study demonstrates that ficolins are important in initial innate host defense against A. fumigatus infections in vivo.

FGF8-FGFR1 signaling acts as a niche factor for maintaining undifferentiated spermatogonia in the mouse

In mammalian testes, spermatogonial stem cells (SSCs) maintain spermatogenesis over a long period of time by undergoing self-renewal and differentiation. SSCs are among the most primitive of spermatogenic cells (undifferentiated spermatogonia), and their activities are strictly regulated by extrinsic niche factors. However, the factors that constitute a testicular niche remain poorly understood. In this study, we demonstrate that fibroblast growth factor (FGF) signaling maintains undifferentiated spermatogonia through activating ERK1/2 signaling in vivo. Undifferentiated spermatogonia comprise GFRA1(+) and NANOS3(+) subpopulations, which are likely to undergo self-renewal and enter the differentiation pathway, respectively. In the testis, Fgfr1 was expressed in the entire population of undifferentiated spermatogonia, and deleting FGFR1 in spermatogenic cells partially inactivated ERK1/2 and resulted in reduced numbers of both GFRA1(+) and NANOS3(+) cells. In addition, Fgf8 was expressed in spermatogenic cells, and loss- and gain-of-function models of FGF8 demonstrated that FGF8 positively regulated the numbers of undifferentiated spermatogonia through FGFR1, particularly among NANOS3(+) cells. Finally we show a possible involvement of FGF signaling in the reversion from NANOS3(+) into GFRA1(+) undifferentiated spermatogonia. Taken together, our data suggest that FGF signaling is an important component of the testicular niche and has a unique function for maintaining undifferentiated spermatogonia.

The Role of fibroblast growth factor receptor substrate 2 (FRS2) in the regulation of two activity levels of the components of the extracellular signal-regulated kinase (ERK) pathway in the mouse epididymis

The components of the extracellular signal-regulated kinase (ERK) pathway are involved in the regulation of epididymal cellular processes. Interestingly, our previous studies showed that there are two different activity levels of the ERK pathway components in the epididymal epithelium: a basal level in most regions and a higher level in the differentiated initial segment (IS). In this study we analyzed the role of fibroblast growth factor receptor substrate 2 (FRS2) in the regulation of these two levels. Two mouse models were generated. In the first model, Frs2 was deleted from epithelial cells of most epididymal regions except for the IS from the embryonic period onward. Loss of Frs2 dampened the basal activity level of the ERK pathway components, which resulted in an increase in apoptosis along the epididymal duct. This was observed during the period when FRS2 expression level was highest in wild-type epididymides. In the second model, Frs2 was deleted from the proximal epididymal epithelium from Postnatal Day 17 onward. Most of the epididymides in this model exhibited normal morphology. Loss of Frs2 in these epididymides did not affect the high activity level of the ERK pathway components in the IS. However, a subgroup of epididymides in the second model showed increased apoptosis which resulted in an abnormally shaped proximal region or development of granulomas. Therefore, data from these two models showed that FRS2 played different roles in the regulation of two activity levels of the ERK pathway components in the epididymis.

Pharmacoresistant Cav 2·3 (E-type/R-type) voltage-gated calcium channels influence heart rate dynamics and may contribute to cardiac impulse conduction

Voltage-gated Ca(2+) channels regulate cardiac automaticity, rhythmicity and excitation-contraction coupling. Whereas L-type (Cav 1·2, Cav 1·3) and T-type (Cav 3·1, Cav 3·2) channels are widely accepted for their functional relevance in the heart, the role of Cav 2·3 Ca(2+) channels expressing R-type currents remains to be elucidated. We have investigated heart rate dynamics in control and Cav 2·3-deficient mice using implantable electrocardiogram radiotelemetry and pharmacological injection experiments. Autonomic block revealed that the intrinsic heart rate does not differ between both genotypes. Systemic administration of isoproterenol resulted in a significant reduction in interbeat interval in both genotypes. It remained unaffected after administering propranolol in Cav 2·3(-|-) mice. Heart rate from isolated hearts as well as atrioventricular conduction for both genotypes differed significantly. Additionally, we identified and analysed the developmental expression of two splice variants, i.e. Cav 2·3c and Cav 2·3e. Using patch clamp technology, R-type currents could be detected in isolated prenatal cardiomyocytes and be related to R-type Ca(2+) channels. Our results indicate that on the systemic level, the pharmacologically inducible heart rate range and heart rate reserve are impaired in Cav 2·3 (-|-) mice. In addition, experiments on Langendorff perfused hearts elucidate differences in basic properties between both genotypes. Thus, Cav 2·3 does not only contribute to the cardiac autonomous nervous system but also to intrinsic rhythm propagation.