Smooth muscle-selective CPI-17 expression increases vascular smooth muscle contraction and blood pressure

An integrated single-cell transcriptomic dataset for non-small cell lung cancer

As single-cell RNA sequencing (scRNA-seq) has emerged as a great tool for studying cellular heterogeneity within the past decade, the number of available scRNA-seq datasets also rapidly increased. However, reuse of such data is often problematic due to a small cohort size, limited cell types, and insufficient information on cell type classification. Here, we present a large integrated scRNA-seq dataset containing 224,611 cells from human primary non-small cell lung cancer (NSCLC) tumors. Using publicly available resources, we pre-processed and integrated seven independent scRNA-seq datasets using an anchor-based approach, with five datasets utilized as reference and the remaining two, as validation. We created two levels of annotation based on cell type-specific markers conserved across the datasets. To demonstrate usability of the integrated dataset, we created annotation predictions for the two validation datasets using our integrated reference. Additionally, we conducted a trajectory analysis on subsets of T cells and lung cancer cells. This integrated data may serve as a resource for studying NSCLC transcriptome at the single cell level.

Possible roles of N- and C-terminal unstructured tails of CPI-17 in regulating Ca²⁺ sensitization force of smooth muscle

CPI-17 regulates the myosin phosphatase and mediates the agonist-induced contraction of smooth muscle. PKC and ROCK phosphorylate CPI-17 at Thr38 leading to a conformational change of the central inhibitory domain (PHIN domain). The N- and C-terminal tails of CPI-17 are predicted as unstructured loops and their sequences are conserved among mammals. Here we characterized CPI-17 N- and C-terminal unstructured tails using recombinant proteins that lack the potions. Recombinant CPI-17 proteins at a physiologic level (10 µM) were doped into beta-escin-permeabilized smooth muscle strips for Ca²⁺ sensitization force measurement. The ectopic full-length CPI-17 augmented the PDBu-induced Ca²⁺ sensitization force at pCa6.3, indicating myosin phosphatase inhibition. Deletion of N- and C-terminal tails of CPI-17 attenuated the extent of PDBu-induced Ca²⁺-sensitization force. The N-terminal deletion dampened phosphorylation at Thr38 by protein kinase C (PKC), and the C-terminal truncation lowered the affinity to the myosin phosphatase. Under the physiologic conditions, PKC and myosin phosphatase may recognize CPI-17 N-/C-terminal unstructured tails inducing Ca²⁺ sensitization force in smooth muscle cells.

Regulation of myosin light-chain phosphorylation and its roles in cardiovascular physiology and pathophysiology

The regulation of muscle contraction is a critical function in the cardiovascular system, and abnormalities may be life-threatening or cause illness. The common basic mechanism in muscle contraction is the interaction between the protein filaments myosin and actin. Although this interaction is primarily regulated by intracellular Ca²⁺, the primary targets and intracellular signaling pathways differ in vascular smooth muscle and cardiac muscle. Phosphorylation of the myosin regulatory light chain (RLC) is a primary molecular switch for smooth muscle contraction. The equilibrium between phosphorylated and unphosphorylated RLC is dynamically achieved through two enzymes, myosin light chain kinase, a Ca²⁺-dependent enzyme, and myosin phosphatase, which modifies the Ca²⁺ sensitivity of contractions. In cardiac muscle, the primary target protein for Ca²⁺ is troponin C on thin filaments; however, RLC phosphorylation also plays a modulatory role in contraction. This review summarizes recent advances in our understanding of the regulation, physiological function, and pathophysiological involvement of RLC phosphorylation in smooth and cardiac muscles.

Characterization of Contractile Machinery of Vascular Smooth Muscles in Hypertension

Hypertension is a key risk factor for cardiovascular disease and it is a growing public health problem worldwide. The pathophysiological mechanisms of vascular smooth muscle (VSM) contraction contribute to the development of hypertension. Calcium (Ca²⁺)-dependent and -independent signaling mechanisms regulate the balance of the myosin light chain kinase and myosin light chain phosphatase to induce myosin phosphorylation, which activates VSM contraction to control blood pressure (BP). Here, we discuss the mechanism of the contractile machinery in VSM, especially RhoA/Rho kinase and PKC/CPI-17 of Ca²⁺ sensitization pathway in hypertension. The two signaling pathways affect BP in physiological and pathophysiological conditions and are highlighted in pulmonary, pregnancy, and salt-sensitive hypertension.

The double face of miR-320: cardiomyocytes-derived miR-320 deteriorated while fibroblasts-derived miR-320 protected against heart failure induced by transverse aortic constriction

MicroRNAs (miRNAs) are aberrantly expressed in the pathophysiologic process of heart failure (HF). However, the functions of a certain miRNA in different cardiac cell types during HF are scarcely reported, which might be covered by the globe effects of it on the heart. In the current study, Langendorff system was applied to isolate cardiomyocytes (CMs) and cardiac fibroblasts (CFs) from transverse aortic constriction (TAC)-induced mice. Slight increase of miR-320 expression was observed in the whole heart tissue of TAC mice. Interestingly, miR-320 was significantly elevated in CMs but decreased in CFs from TAC mice at different time points. Then, recombinant adeno-associated virus 9 with cell-type-specific promoters were used to manipulate miR-320 expressions in vivo. Both in vitro and in vivo experiments showed the miR-320 overexpression in CMs exacerbated cardiac dysfunction, whereas overexpression of miR-320 in CFs alleviated cardiac fibrosis and hypertrophy. Mechanically, downstream signaling pathway analyses revealed that miR-320 might induce various effects via targeting PLEKHM3 and IFITM1 in CMs and CFs, respectively. Moreover, miR-320 mediated effects could be abolished by PLEKHM3 re-expression in CMs or IFITM1 re-expression in CFs. Interestingly, miR-320 treated CFs were able to indirectly affect CMs function, but not vice versa. Meanwhile, upstream signaling pathway analyses showed that miR-320 expression and decay rate were rigorously manipulated by Ago2, which was regulated by a cluster of cell-type-specific TFs distinctively expressed in CMs and CFs, respectively. Together, we demonstrated that miR-320 functioned differently in various cell types of the heart during the progression of HF.

Transcriptional and Functional Changes of the Human Microvasculature during Physiological Aging and Alzheimer Disease

Aging of the circulatory system correlates with the pathogenesis of a large spectrum of diseases. However, it is largely unknown which factors drive the age-dependent or pathological decline of the vasculature and how vascular defects relate to tissue aging. The goal of the study is to design a multianalytical approach to identify how the cellular microenvironment (i.e., fibroblasts) and serum from healthy donors of different ages or Alzheimer disease (AD) patients can modulate the functionality of organ-specific vascular endothelial cells (VECs). Long-living human microvascular networks embedding VECs and fibroblasts from skin biopsies are generated. RNA-seq, secretome analyses, and microfluidic assays demonstrate that fibroblasts from young donors restore the functionality of aged endothelial cells, an effect also achieved by serum from young donors. New biomarkers of vascular aging are validated in human biopsies and it is shown that young serum induces angiopoietin-like-4, which can restore compromised vascular barriers. This strategy is then employed to characterize transcriptional/functional changes induced on the blood-brain barrier by AD serum, demonstrating the importance of PTP4A3 in the regulation of permeability. Features of vascular degeneration during aging and AD are recapitulated, and a tool to identify novel biomarkers that can be exploited to develop future therapeutics modulating vascular function is established.

RNA-Sequencing Analysis Reveals l-Theanine Regulating Transcriptional Rhythm Alteration in Vascular Smooth Muscle Cells Induced by Dexamethasone

l-Theanine, a unique amino acid in tea leaves, is known to have beneficial effects on stress relief, tumor suppression, and prevention of hypertension and cardiovascular diseases (CADs). The disruption of the circadian rhythm has been implied in the pathogenesis of CADs. However, it is unknown whether l-theanine has a modulatory effect on the vascular circadian rhythm. In this research, we have established a circadian gene expression model in rat vascular smooth muscle cells by dexamethasone induction. l-Theanine treatment enhanced the expression amplitude of clock genes, including Bmal1, Cry1, Rev-erbα, and Per2. Moreover, pairwise comparisons of the RNA-sequencing data showed that l-theanine is able to upregulate a ray of the rhythm genes and differentially expressed genes that are involved in vasoconstriction and actin cytoskeleton regulation pathways. Our data suggest that l-theanine changes the circadian gene rhythm involving in the process of vascular smooth muscle restructure.

Transcriptional Suppression of CPI-17 Gene Expression in Vascular Smooth Muscle Cells by Tumor Necrosis Factor, Krüppel-Like Factor 4, and Sp1 Is Associated with Lipopolysaccharide-Induced Vascular Hypocontractility, Hypotension, and Mortality

Vasodilatory shock in sepsis is caused by the failure of the vasculature to respond to vasopressors, which results in hypotension, multiorgan failure, and ultimately patient death. Recently, it was reported that CPI-17, a key player in the regulation of smooth muscle contraction, was downregulated by lipopolysaccharide (LPS) in mesenteric arteries concordant with vascular hypocontractilty.

Vasodilatory shock in sepsis is caused by the failure of the vasculature to respond to vasopressors, which results in hypotension, multiorgan failure, and ultimately patient death. Recently, it was reported that CPI-17, a key player in the regulation of smooth muscle contraction, was downregulated by lipopolysaccharide (LPS) in mesenteric arteries concordant with vascular hypocontractilty. While Sp1 has been shown to activate CPI-17 transcription, it is unknown whether Sp1 is involved in LPS-induced smooth muscle CPI-17 downregulation. Here we report that tumor necrosis factor (TNF) was critical for LPS-induced smooth muscle CPI-17 downregulation. Mechanistically, we identified two GC boxes as a key TNF response element in the CPI-17 promoter and demonstrated that KLF4 was upregulated by TNF, competed with Sp1 for the binding to the GC boxes in the CPI-17 promoter, and repressed CPI-17 transcription through histone deacetylases (HDACs). Moreover, genetic deletion of TNF or pharmacological inhibition of HDACs protected mice from LPS-induced smooth muscle CPI-17 downregulation, vascular hypocontractility, hypotension, and mortality. In summary, these data provide a novel mechanism of the transcriptional control of CPI-17 in vascular smooth muscle cells under inflammatory conditions and suggest a new potential therapeutic strategy for the treatment of vasodilatory shock in sepsis.

Angiotensin II Signal Transduction: An Update on Mechanisms of Physiology and Pathophysiology

The renin-angiotensin-aldosterone system plays crucial roles in cardiovascular physiology and pathophysiology. However, many of the signaling mechanisms have been unclear. The angiotensin II (ANG II) type 1 receptor (AT₁R) is believed to mediate most functions of ANG II in the system. AT₁R utilizes various signal transduction cascades causing hypertension, cardiovascular remodeling, and end organ damage. Moreover, functional cross-talk between AT₁R signaling pathways and other signaling pathways have been recognized. Accumulating evidence reveals the complexity of ANG II signal transduction in pathophysiology of the vasculature, heart, kidney, and brain, as well as several pathophysiological features, including inflammation, metabolic dysfunction, and aging. In this review, we provide a comprehensive update of the ANG II receptor signaling events and their functional significances for potential translation into therapeutic strategies. AT₁R remains central to the system in mediating physiological and pathophysiological functions of ANG II, and participation of specific signaling pathways becomes much clearer. There are still certain limitations and many controversies, and several noteworthy new concepts require further support. However, it is expected that rigorous translational research of the ANG II signaling pathways including those in large animals and humans will contribute to establishing effective new therapies against various diseases.

A Novel Diabetic Mouse Model for Real-Time Monitoring of Clock Gene Oscillation and Blood Pressure Circadian Rhythm

Diabetic patients have an increased prevalence of blood pressure (BP) circadian rhythm disruption, which is associated with an increased risk of target organ damage and detrimental cardiovascular events. Limited information is available regarding the role of clock genes in the disruption of BP circadian rhythm in diabetes due to the lack of a diabetic animal model that allows real-time monitoring of clock gene oscillation. Here, we generated a novel diabetic db/db-mPer2^Luc mouse model by crossing type 2 diabetic db/db mice with mPer2^Luc knock-in mice. The daily rhythms of BP, heart rate, locomotor activity, and food and water intake were acquired by radiotelemetry or using metabolic chambers. The daily oscillation of mPer2 bioluminescence was recorded by LumiCycle in real-time in tissue explants and using the IVIS system in vivo. Our results show that db/db-mPer2^Luc mice are obese, diabetic, and glucose intolerant. The db/db-mPer2^Luc mice displayed a compromised BP daily rhythm, which was associated with disrupted daily rhythms in baroreflex sensitivity, locomotor activity, and metabolism, but not heart rate or food and water intake. The phase of the mPer2 daily oscillation was advanced to different extents in the explanted peripheral tissues from db/db-mPer2^Luc mice relative to control mice. In contrast, no phase shift was detected in mPer2 daily oscillations in the explanted SCN. Moreover, advanced phase shift of the mPer2 daily oscillation was detected in the liver, kidney and submandibular gland in vivo of db/db-mPer2^Luc mice. In conclusion, the diabetic db/db-mPer2^Luc mouse is a novel animal model that allows real-time monitoring of mPer2 circadian rhythms ex vivo and in vivo. The results from db/db-mPer2^Luc mice suggest that the desynchrony of mPer2 daily oscillation in peripheral tissues contributes to the loss of BP daily oscillation in diabetes.

Induction of myosin light chain kinase and CPI-17 by TGF-β accelerates contractile activity in intestinal epithelial cells

Epithelial-mesenchymal transition (EMT) is an orchestral and functional change in epithelial cells. Many signaling pathways are involved in EMT, and transforming growth factor-beta (TGF-β) is considered to be one of the most important factors in induction of EMT. In this study, we treated the rat intestinal epithelial cell line (IEC-6) with TGF-β1 as a signaling stimulant. Gross analysis of IEC-6 cells showed typical characteristics of epithelial cells such as cuboidal morphology and cell-cell contact, whereas treatment with TGF-β1 (10 ng/ml^-1) for 7 days produced robust, spindle-shaped morphology. Immunocytochemistry analysis showed distinct E-cadherin staining in IEC-6 cells, but weak and faint in EMT cells. EMT cells showed positive expression of α-SMA and tenascin-C but IEC-6 cells did not. Quantitative real-time PCR analysis showed that myosin light chain kinase and C-kinase potentiated protein phosphatase-1 inhibitor (CPI-17) mRNAs were significantly upregulated in EMT cells. Immunocytochemistry analysis also showed that EMT cells strongly expressed CPI-17 but IEC-6 cells did not. A collagen gel contraction assay revealed that EMT cells had greatly increased contraction compared with control cells. These results suggest that the increased contractile activity induced by TGF-β in EMT cells may be attributable to the upregulation of molecules responsible for myosin phosphorylation/de-phosphorylation.

S-adenosyl methionine regulates calcium channels and inhibits uterine smooth muscle contraction in rats with infectious premature delivery through the transient receptor protein 3/protein kinase Cβ/C-kinase-activated protein phosphatase-1 inhibitor of 17 kDa signaling pathway

The aim of the present study was to investigate the effects of S-adenosyl methionine (SAMe) on infectious premature inflammatory factors and uterine contraction, and to further explore its mechanism of action via the transient receptor protein 3 (TRPC3)/protein kinase Cβ (PKCβ)/C-kinase-activated protein phosphatase-1 inhibitor of 17 kDa (CPI-17) signaling pathway, following intervention by a TRPC3 inhibitor. A rat model of premature delivery induced by lipopolysaccharide (LPS) was established. Following treatment with SAMe and inhibiting TRPC3 expression, rat serum and uterus were isolated. Hematoxylin and eosin staining was used to observe the histopathological changes in the uterus. Uterine muscle strips in vitro were selected to measure the changes in muscle tension. ELISA was utilized to measure the changes in serum inflammatory factor and oxidative stress indexes. Immunohistochemistry, western blot assay and reverse transcription-quantitative polymerase chain reaction were applied to detect calcium channel protein expression in the uterus. Western blot analysis was employed to measure the expression of TRPC3/PKCβ/CPI-17 signaling pathway-related proteins. TRPC3 was highly expressed in the uterus of rat models of premature delivery induced by LPS. Following treatment with SAMe, inflammatory cell infiltration markedly reduced in the uterus and the tension of in vitro uterine muscle strips significantly decreased. SAMe treatment suppressed inflammatory reaction and oxidative stress, and diminished L-type and T-type calcium channel protein expression. TRPC3/PKCβ/CPI-17 signaling pathway-related protein expression was also reduced. When TRPC3 expression was suppressed, the effects of SAMe against inflammation and oxidative stress were diminished. TRPC3/PKCβ/CPI-17 signaling pathway-related protein expression significantly increased. SAMe was able to reduce inflammatory reaction and oxidative stress in the uterus of rat model of infectious premature delivery induced by LPS, prolong delivery time, reduce the mortality rate of offspring rats, and serve a therapeutic role. This effect is likely achieved via the regulation of uterine contractions and childbirth through the TRPC3/PKCβ/CPI-17 signaling pathway.

Diversity and plasticity in signaling pathways that regulate smooth muscle responsiveness: Paradigms and paradoxes for the myosin phosphatase, the master regulator of smooth muscle contraction

A hallmark of smooth muscle cells is their ability to adapt their functions to meet temporal and chronic fluctuations in their demands. These functions include force development and growth. Understanding the mechanisms underlying the functional plasticity of smooth muscles, the major constituent of organ walls, is fundamental to elucidating pathophysiological rationales of failures of organ functions. Also, the knowledge is expected to facilitate devising innovative strategies that more precisely monitor and normalize organ functions by targeting individual smooth muscles. Evidence has established a current paradigm that the myosin light chain phosphatase (MLCP) is a master regulator of smooth muscle responsiveness to stimuli. Cellular MLCP activity is negatively and positively regulated in response to G-protein activation and cAMP/cGMP production, respectively, through the MYPT1 regulatory subunit and an endogenous inhibitor protein named CPI-17. In this article we review the outcomes from two decade of research on the CPI-17 signaling and discuss emerging paradoxes in the view of signaling pathways regulating smooth muscle functions through MLCP.

Regional Heterogeneity in the Regulation of Vasoconstriction in Arteries and Its Role in Vascular Mechanics

Vasoconstriction and vasodilation play important roles in the circulatory system and can be regulated through different pathways that depend on myriad biomolecules. These different pathways reflect the various functions of smooth muscle cell (SMC) contractility within the different regions of the arterial tree and how they contribute to both the mechanics and the mechanobiology. Here, we review the primary regulatory pathways involved in SMC contractility and highlight their regional differences in elastic, muscular, and resistance arteries. In this way, one can begin to assess how these properties affect important biomechanical and mechanobiological functions in the circulatory system in health and disease.

Roles and mechanisms of TRPC3 and the PLCγ/PKC/CPI-17 signaling pathway in regulating parturition

The aim of the current study was to investigate the role of phospholipase C (PLC)γ/protein kinase C (PKC)/C-kinase-activated protein phosphatase-1 (CPI-17) signaling pathways in uterine smooth muscle during parturition. Samples of uterine tissue were collected from pregnant patients who underwent a caesarean section for preterm delivery, full-term delivery with labor onset, full-term delivery without labor onset, and from a non-pregnant control group undergoing surgery for cervical intraepithelial neoplasia III. Immunohistochemistry, and western blotting were used to assess the association between TRPC3 levels and parturition and the influence of calcium ion channels. In addition, pregnant mice were used to explore the effect of uterine canonical transient receptor potential 3 (TRPC3) expression on the parturition-triggering mechanism and PLCγ/PKC/CPI-17 signaling pathways. Pregnant mouse uterine smooth muscle cells were cultivated, with and without TRPC3 silencing, and the expression levels of PLCγ, PKC and CPI-17, the upstream and downstream factors of the TRPC3 pathway, were measured in pregnant mouse uterine smooth muscle cells, in order to provide a theoretical basis for the prevention and treatment of premature labor. In the preterm and full-term without labor onset patient groups, the TRPC3 gene expression in the mSMCs was significantly overexpressed when compared with the non-pregnant group (P<0.05); however, TRPC3 expression was not elevated in the full-term with labor onset group, exhibiting no significant difference compared with the non-pregnant group (P>0.05). During pregnancy, compared with the non-pregnant controls, Ca_v1.2, Ca_v3.1 and Ca_v3.2 gene expression levels were markedly increased (P<0.05) in mSMCs from the preterm delivery group and the full-term with labor onset group, however were non-significantly increased in the full-term without labor onset group. The level of TRPC3 was highest in the preterm group, while the levels of Ca_v1.2, Ca_v3.1 and Ca_v3.2 were highest in the full-term with labor onset group. In the preterm, LPS-treated preterm and full-term groups, TRPC3, MAPK, ERK1/2, P-ERK, Ca_v3.2, Ca_v3.1 and Ca_v1.2 were all expressed at higher levels than in the unfertilized group. In the LPS-treated preterm group, the levels of TRPC3, MAPK, ERK1/2, P-ERK, Ca_v3.2, Ca_v3.1 and Ca_v1.2 were increased compared with the preterm group. Furthermore, following transfection of small interfering TRPC3 (siTRPC3) into cells, it was demonstrated that the levels of TRPC3, PLCγ, PKC, CPI-17, P-CPI-17, Ca_v1.2, Ca_v3.1 and Ca_v3.2 expression were lower in the LPS siTRPC3 group when compared with that of the LPS-treated untransfected control group.

X-ray irradiation has positive effects for the recovery of peripheral nerve injury maybe through the vascular smooth muscle contraction signaling pathway

INTRODUCTION

It is well known that moderate to high doses of ionizing radiation have a toxic effect on the organism. However, there are few experimental studies on the mechanisms of LDR ionizing radiation on nerve regeneration after peripheral nerve injury.

METHODS

We established the rats' peripheral nerve injury model via repaired Peripheral nerve injury nerve, vascular endothelial growth factor a and Growth associated protein-43 were detected from different treatment groups. We performed transcriptome sequencing focusing on investigating the differentially expressed genes and gene functions between the control group and 1Gy group. Sequencing was done by using high-throughput RNA-sequencing (RNA-seq) technologies.

RESULTS

The results showed the 1Gy group to be the most effective promoting repair. RNA-sequencing identified 619 differently expressed genes between control and treated groups. A Gene Ontology analysis of the differentially expressed genes revealed enrichment in the functional pathways. Among them, candidate genes associated with nerve repair were identified.

DISCUSSION

Pathways involved in cell-substrate adhesion, vascular smooth muscle contraction and cell adhesion molecule signaling may be involved in recovery from peripheral nerve injury.

Protein phosphatases 1 and 2A and their naturally occurring inhibitors: current topics in smooth muscle physiology and chemical biology

Protein phosphatases 1 and 2A (PP1 and PP2A) are the most ubiquitous and abundant serine/threonine phosphatases in eukaryotic cells. They play fundamental roles in the regulation of various cellular functions. This review focuses on recent advances in the functional studies of these enzymes in the field of smooth muscle physiology. Many naturally occurring protein phosphatase inhibitors with different relative PP1/PP2A affinities have been discovered and are widely used as powerful research tools. Current topics in the chemical biology of PP1/PP2A inhibitors are introduced and discussed, highlighting the identification of the gene cluster responsible for the biosynthesis of calyculin A in a symbiont microorganism of a marine sponge.

Neural programming of mesenteric and renal arteries

There is evidence for developmental origins of vascular dysfunction yet little understanding of maturation of vascular smooth muscle (VSM) of regional circulations. We measured maturational changes in expression of myosin phosphatase (MP) and the broader VSM gene program in relation to mesenteric small resistance artery (SRA) function. We then tested the role of the sympathetic nervous system (SNS) in programming of SRAs and used genetically engineered mice to define the role of MP isoforms in the functional maturation of the mesenteric circulation. Maturation of rat mesenteric SRAs as measured by qPCR and immunoblotting begins after the second postnatal week and is not complete until maturity. It is characterized by induction of markers of VSM differentiation (smMHC, γ-, α-actin), CPI-17, an inhibitory subunit of MP and a key target of α-adrenergic vasoconstriction, α1-adrenergic, purinergic X1, and neuropeptide Y1 receptors of sympathetic signaling. Functional correlates include maturational increases in α-adrenergic-mediated force and calcium sensitization of force production (MP inhibition) measured in first-order mesenteric arteries ex vivo. The MP regulatory subunit Mypt1 E24+/LZ- isoform is specifically upregulated in SRAs during maturation. Conditional deletion of mouse Mypt1 E24 demonstrates that splicing of E24 causes the maturational reduction in sensitivity to cGMP-mediated vasorelaxation (MP activation). Neonatal chemical sympathectomy (6-hydroxydopamine) suppresses maturation of SRAs with minimal effect on a conduit artery. Mechanical denervation of the mature rat renal artery causes a reversion to the immature gene program. We conclude that the SNS captures control of the mesenteric circulation by programming maturation of the SRA smooth muscle.

Myosin phosphatase isoforms as determinants of smooth muscle contractile function and calcium sensitivity of force production

The dephosphorylation of myosin by the MP causes smooth muscle relaxation. MP is also a key target of signals that regulate vascular tone and thus blood flow and pressure. Here, we review studies from the past two decades that support the hypothesis that the regulated expression of MP subunits is a critical determinant of smooth muscle responses to constrictor and dilator signals. In particular, the highly regulated splicing of the regulatory subunit Mypt1 Exon 24 is proposed to tune sensitivity to NO/cGMP-mediated relaxation. The regulated transcription of the MP inhibitory subunit CPI-17 is proposed to determine sensitivity to agonist-mediated constriction. The expression of these subunits is specific in the microcirculation and varies in developmental and disease contexts. To date, the relationship between MP subunit expression and vascular function in these different contexts is correlative; confirmation of the hypothesis will require the generation of genetically engineered mice to test the role of MP subunits and their isoforms in the specificity of vascular smooth muscle responses to constrictor and dilator signals.

Redox signaling and splicing dependent change in myosin phosphatase underlie early versus late changes in NO vasodilator reserve in a mouse LPS model of sepsis

Microcirculatory dysfunction may cause tissue malperfusion and progression to organ failure in the later stages of sepsis, but the role of smooth muscle contractile dysfunction is uncertain. Mice were given intraperitoneal LPS, and mesenteric arteries were harvested at 6-h intervals for analyses of gene expression and contractile function by wire myography. Contractile (myosin and actin) and regulatory [myosin light chain kinase and phosphatase subunits (Mypt1, CPI-17)] mRNAs and proteins were decreased in mesenteric arteries at 24 h concordant with reduced force generation to depolarization, Ca(2+), and phenylephrine. Vasodilator sensitivity to DEA/nitric oxide (NO) and cGMP under Ca(2+) clamp were increased at 24 h after LPS concordant with a switch to Mypt1 exon 24- splice variant coding for a leucine zipper (LZ) motif required for PKG-1α activation of myosin phosphatase. This was reproduced by smooth muscle-specific deletion of Mypt1 exon 24, causing a shift to the Mypt1 LZ+ isoform. These mice had significantly lower resting blood pressure than control mice but similar hypotensive responses to LPS. The vasodilator sensitivity of wild-type mice to DEA/NO, but not cGMP, was increased at 6 h after LPS. This was abrogated in mice with a redox dead version of PKG-1α (Cys42Ser). Enhanced vasorelaxation in early endotoxemia is mediated by redox signaling through PKG-1α but in later endotoxemia by myosin phosphatase isoform shifts enhancing sensitivity to NO/cGMP as well as smooth muscle atrophy. Muscle atrophy and modulation may be a novel target to suppress microcirculatory dysfunction; however, inactivation of inducible NO synthase, treatment with the IL-1 antagonist IL-1ra, or early activation of α-adrenergic signaling did not suppressed this response.

Smooth-muscle BMAL1 participates in blood pressure circadian rhythm regulation

As the central pacemaker, the suprachiasmatic nucleus (SCN) has long been considered the primary regulator of blood pressure circadian rhythm; however, this dogma has been challenged by the discovery that each of the clock genes present in the SCN is also expressed and functions in peripheral tissues. The involvement and contribution of these peripheral clock genes in the circadian rhythm of blood pressure remains uncertain. Here, we demonstrate that selective deletion of the circadian clock transcriptional activator aryl hydrocarbon receptor nuclear translocator-like (Bmal1) from smooth muscle, but not from cardiomyocytes, compromised blood pressure circadian rhythm and decreased blood pressure without affecting SCN-controlled locomotor activity in murine models. In mesenteric arteries, BMAL1 bound to the promoter of and activated the transcription of Rho-kinase 2 (Rock2), and Bmal1 deletion abolished the time-of-day variations in response to agonist-induced vasoconstriction, myosin phosphorylation, and ROCK2 activation. Together, these data indicate that peripheral inputs contribute to the daily control of vasoconstriction and blood pressure and suggest that clock gene expression outside of the SCN should be further evaluated to elucidate pathogenic mechanisms of diseases involving blood pressure circadian rhythm disruption.

Short-term cuprizone feeding verifies N-acetylaspartate quantification as a marker of neurodegeneration

Proton magnetic resonance spectroscopy (1H-MRS) is a quantitative MR imaging technique often used to complement conventional MR imaging with specific metabolic information. A key metabolite is the amino acid derivative N-Acetylaspartate (NAA) which is an accepted marker to measure the extent of neurodegeneration in multiple sclerosis (MS) patients. NAA is catabolized by the enzyme aspartoacylase (ASPA) which is predominantly expressed in oligodendrocytes. Since the formation of MS lesions is paralleled by oligodendrocyte loss, NAA might accumulate in the brain, and therefore, the extent of neurodegeneration might be underestimated. In the present study, we used the well-characterized cuprizone model. There, the loss of oligodendrocytes is paralleled by a reduction in ASPA expression and activity as demonstrated by genome-wide gene expression analysis and enzymatic activity assays. Notably, brain levels of NAA were not increased as determined by gas chromatography-mass spectrometry and 1H-MRS. These important findings underpin the reliability of NAA quantification as a valid marker for the paraclinical determination of the extent of neurodegeneration, even under conditions of oligodendrocyte loss in which impaired metabolization of NAA is expected. Future studies have to reveal whether other enzymes are able to metabolize NAA or whether an excess of NAA is cleared by other mechanisms rather than enzymatic metabolism.

Myosin phosphatase isoforms and related transcripts in the pig coronary circulation and effects of exercise and chronic occlusion

Myosin phosphatase (MP) is a key target of signaling pathways that regulate smooth muscle tone and blood flow. Alternative splicing of MP targeting subunit (MYPT1) exon 24 (E24) generates isoforms with variable presence of a C-terminal leucine zipper (LZ) required for activation of MP by NO/cGMP. Here we examined the expression of MP and associated genes in a disease model in the coronary circulation. Female Yucatan miniature swine remained sedentary or were exercise-trained beginning eight weeks after placement of an ameroid constrictor around the left circumflex (LCX) artery. Fourteen weeks later epicardial arteries (~1mm) and resistance arterioles (~125 μm) were harvested and assayed for gene expression. MYPT1 isoforms were distinct in the epicardial arteries (E24-/LZ+) and resistance arterioles (E24+/LZ-) and unchanged by exercise training or coronary occlusion. MYPT1, CPI-17 and PDE5 mRNA levels were not different between arteries and arterioles while Kir2.1 and eNOS were 6.6-fold and 3.9-fold higher in the arterioles. There were no significant changes in transcript abundance in epicardial arteries of the collateralized (LCX) vs. non-occluded left anterior descending (LAD) territories, or in exercise-trained vs. sedentary pigs. There was a significant 1.2 fold increase in CPI-17 in collateral-dependent arterioles, independent of exercise, and a significant 1.7 fold increase in PDE5 in arterioles from exercise-trained pigs, independent of occlusion. We conclude that differences in MYPT1 E24 (LZ) isoforms, eNOS, and Kir2.1 distinguish epicardial arteries and resistance coronary arterioles. Up-regulation of coronary arteriolar PDE5 by exercise and CPI-17 by chronic occlusion could contribute to altered vasomotor responses and requires further study.

Disruption of vascular Ca2+-activated chloride currents lowers blood pressure

High blood pressure is the leading risk factor for death worldwide. One of the hallmarks is a rise of peripheral vascular resistance, which largely depends on arteriole tone. Ca2+-activated chloride currents (CaCCs) in vascular smooth muscle cells (VSMCs) are candidates for increasing vascular contractility. We analyzed the vascular tree and identified substantial CaCCs in VSMCs of the aorta and carotid arteries. CaCCs were small or absent in VSMCs of medium-sized vessels such as mesenteric arteries and larger retinal arterioles. In small vessels of the retina, brain, and skeletal muscle, where contractile intermediate cells or pericytes gradually replace VSMCs, CaCCs were particularly large. Targeted disruption of the calcium-activated chloride channel TMEM16A, also known as ANO1, in VSMCs, intermediate cells, and pericytes eliminated CaCCs in all vessels studied. Mice lacking vascular TMEM16A had lower systemic blood pressure and a decreased hypertensive response following vasoconstrictor treatment. There was no difference in contractility of medium-sized mesenteric arteries; however, responsiveness of the aorta and small retinal arterioles to the vasoconstriction-inducing drug U46619 was reduced. TMEM16A also was required for peripheral blood vessel contractility, as the response to U46619 was attenuated in isolated perfused hind limbs from mutant mice. Out data suggest that TMEM16A plays a general role in arteriolar and capillary blood flow and is a promising target for the treatment of hypertension.