Myosin Light Chain Phosphorylation Research Articles

Inflammatory responses and barrier disruption in the trachea of chicks following Mycoplasma gallisepticum infection: a focus on the TNF-α-NF-κB/MLCK pathway

Mycoplasma gallisepticum (MG) can induce persistent inflammatory damage to the tracheal mucosa of poultry and cause chronic respiratory diseases in chickens. To further investigate the mechanism of MG-induced injury to the tracheal mucosa, we used chick embryo tracheal organ culture (TOC) as a model to study the invasion and reproduction of MG, the effect of MG on tracheal morphology, and the potential factors that promote MG tissue invasion. The results showed that MG infection significantly damaged the tracheal epithelial structure and weakened tracheal epithelial barrier function; MG also increased the occurrence of bacterial displacement, with a significant (p < 0.05) increase in the bacterial load of the infected TOCs at 5 and 7 days post-infection. In addition, MG significantly (p < 0.05) increased the expression levels of inflammatory cytokines, such as TNF-α, interleukin-1β (IL-1β), and IL-6, and activated the NF-κB signalling pathway, leading to increased nuclear translocation of NF-κB p65. Simultaneously, the map kinase pathway (MAPK) was activated. This activation might be associated with increased myosin light chain (MLC) phosphorylation, which could lead to actin-myosin contraction and disruption of tight junction (TJ) protein function, potentially compromising epithelial barrier integrity and further catalysing MG migration into tissues. Overall, our results contribute to a better understanding of the interaction between MG and the host, provide insight into the mechanisms of damage to the tracheal mucosa induced by MG infection, and provide new insights into the possible pathways involved in Mycoplasma gallisepticum infection in vivo.

GW4064 inhibits migration and invasion through cathepsin B and MMP2 downregulation in human bladder cancer

The ability of bladder cancer to invade and metastasize often leads to poor prognosis in bladder cancer patients. The aim of this study was to evaluate the effect of the farnesoid X receptor (FXR) agonist GW4064 on the migration and invasion of human bladder cancer cells. Long-term exposure to GW4064 decreased the colony formation of RT4 and T24 cells. The wound healing migration assay revealed an inhibitory effect of GW4064 on both of these bladder cancer cell lines. In addition, integrin β3 expression and myosin light chain phosphorylation were decreased after GW4064 treatment. Immunocytochemistry showed an increase in E-cadherin and a decrease in β-catenin in the cell membrane of bladder cancer cells. Total protein expression and membrane fractionation assays also indicated upregulation of E-cadherin and downregulation of β-catenin. Moreover, GW4064 reduced the invasion of muscle-invasive T24 cells. The GW4064-decreased migration and invasion were reversed by the proteasome inhibitor MG132 and the lysosome inhibitor NH4Cl. Furthermore, the GW4064-induced inhibition of matrix metalloproteinase-2 (MMP2) and cathepsin B expression was reversed by NH4Cl. Xenograft animal studies revealed that GW4064 declined MMP2, cathepsin B and lung metastasis of bladder cancer. In conclusion, GW4064 decreases the migration and invasion of human bladder cancer cells, which may provide a new therapeutic strategy for the treatment of human bladder cancer.

Differential expression of the enzymes regulating myosin light chain phosphorylation are responsible for the slower relaxation of pulmonary artery than mesenteric artery in rats.

While arterial tone is generally determined by the phosphorylation of Ser19 in myosin light chain (p-MLC2), Thr18/Ser19 diphosphorylation of MLC2 (pp-MLC2) has been suggested to hinder the relaxation of smooth muscle. In a dual-wire myography of rodent pulmonary artery (PA) and mesenteric artery (MA), we noticed significantly slower relaxation in PA than in MA after 80 mM KCl-induced condition (80K-contraction). Thus, we investigated the MLC2 phosphorylation and the expression levels of its regulatory enzymes; soluble guanylate cyclase (sGC), Rho-A dependent kinase (ROCK) and myosin light chain phosphatase target regulatory subunit (MYPT1). Immunoblotting showed higher sGC-α and ROCK2 in PA than MA, while sGC-β and MYPT1 levels were higher in MA than in PA. Interestingly, the level of pp-MLC2 was higher in PA than in MA without stimulation. In the 80K-contraction state, the levels of p-MLC2 and pp-MLC2 were commonly increased. Treatment with the ROCK inhibitor (Y27632, 10 μM) reversed the higher pp-MLC2 in PA. In the myography study, pharmacological inhibition of sGC (ODQ, 10 μM) slowed relaxation during washout, which was more pronounced in PA than in MA. The simultaneous treatment of Y27632 and ODQ reversed the impaired relaxation in PA and MA. Although treatment of PA with Y27632 alone could increase the rate of relaxation, it was still slower than that of MA without Y27632 treatment. Taken together, we suggest that the higher ROCK and lower MYPT in PA would have induced the higher level of MLC2 phosphorylation, which is responsible for the characteristic slow relaxation in PA.

Rebalancing TGF-β/PGE2 breaks RT-induced immunosuppressive barriers by enhancing tumor-infiltrated dendritic cell homing.

A better understanding of how tumor microenvironments shape immune responses after radiotherapy (RT) is required to improve patient outcomes. This study focuses on the observation that dendritic cells (DCs) infiltrating irradiated cervical tumors are retained in transforming growth factor (TGF)-β-abundant regions. We report that TGF-β secretion from cervical cancer cells was increased by irradiation in a dose-dependent manner and that this significantly suppressed the expression of allostimulatory markers and Th1 cytokines in DCs. To investigate further, we blocked the TGF-β signal in DCs and observed that RT had a dose-dependent immune-promoting effect, improving DC maturation. This suggested that proinflammatory mediators may also be induced by RT, but their effects were being counteracted by the simultaneously increased levels of TGF-β. Prostaglandin E2 (PGE2), a proinflammatory molecule, was shown to be one such mediator. Adjusting the TGF-β/PGE2 ratio by inhibiting TGF-β rebooted RT-induced DC cytoskeletal organization by stimulating myosin light chain (MLC) phosphorylation. Consequently, the homing of intra-tumorally infiltrated DCs to tumor-draining lymph nodes was enhanced, leading to the induction of more robust cytotoxic T cells. Ultimately, rebalancing the TGF-β/PGE2 ratio amplified the therapeutic effects of RT, resulting in increased intra-tumoral infiltration and activation of CD8+ T cells, and improved tumor control and overall survival rate in mice. DC depletion experiments verified that the improvement in tumor control is directly correlated with the involvement of DCs via the PGE2-MLC pathway. This study emphasizes the importance of maintaining a balanced cytokine environment during RT, particularly hypofractionated RT; and it is advisable to block TGF-β while preserving PGE2 in the tumor microenvironment in order to better stimulate DC homing and DC -T priming.

The Cdc42/Rac1 pathway: a molecular mechanism behind iron-deficiency-driven aortic medial degeneration.

To elucidate the underlying mechanism of iron deficiency augmented Angiotensin II-induced aortic medial degeneration. ApoE-/- mice were randomly divided into four groups: normal control group (NC group), Angiotensin II (Ang II) subcutaneous pumped alone Group (Ang II group), iron deficiency (ID) group (ID group) and ID+Ang II group. The survival time, systolic blood pressure (SBP), and aortic medial degeneration (AMD) formation were monitored. Iron deposition in the aortas was assessed using Prussian blue iron staining. The expression of iron metabolism indicators, aortopathies and the cytoskeleton of vascular smooth muscle cells (VSMCs) were analyzed. In an in vitro setting, deferoxamine (DFO) was employed to mimic ID to examine the effects of Ang II on the cytoskeletal and contractile function of VSMCs during ID. Ras-related C3 botulinum toxin substrate 1 (Rac-1) expression was inhibited with EHT1864 to verify the role of Cdc42/Rac1 pathway in this pathological process. Blood samples were collected from 150 patients with aortic dissection (AD) and 60 patients with hypertension who were admitted to the Department of Cardiovascular Surgery at Renmin Hospital of Wuhan University between June 2018 and September 2019. The aortic tissues were obtained during the surgical treatment of Stanford type A AD patients and the heart donor. The iron metabolism status in plasma and aortic tissue was analyzed. In vivo experiments revealed that, in comparison to the NC and ID groups, mice in the Ang II and ID+Ang II groups exhibited increased SBP, significantly reduced survival time, and an expanded range of aortic dissection (P < 0.05). ID feeding augmented the Ang II-induced aortopathies. Both in vitro and in vivo results indicated that ID led to diminished expression of phosphorylated myosin light chain (p-MLC) and recombinant Cell Division Cycle Protein 42 (Cdc42) in VSMCs, while Rac-1 expression increased. The clinical sample testing data further confirmed the discovery that individuals diagnosed with AD display ID in both the plasma and the diseased aortas. The Cdc42/Rac1 pathway plays a crucial role in disrupting the cytoskeleton of vascular smooth muscle cells during iron deficiency, which leads to aortic medial degeneration both in vivo and in vitro.

Everolimus-induced hyperpermeability of endothelial cells causes lung injury.

The mammalian target of rapamycin (mTOR) inhibitors, everolimus (but not dactolisib), is frequently associated with lung injury in clinical therapies. However, the underlying mechanisms remain unclear. Endothelial cell barrier dysfunction plays a major role in the pathogenesis of the lung injury. This study hypothesizes that everolimus increases pulmonary endothelial permeability, which leads to lung injury. We tested the effects of everolimus on human pulmonary microvascular endothelial cell (HPMEC) permeability and a mouse model of intraperitoneal injection of everolimus was established to investigate the effect of everolimus on pulmonary vascular permeability. Our data showed that everolimus increased human pulmonary microvascular endothelial cell (HPMEC) permeability which was associated with MLC phosphorylation and F-actin stress fiber formation. Furthermore, everolimus induced an increasing concentration of intracellular calcium Ca2+ leakage in HPMECs and this was normalized with ryanodine pretreatment. In addition, ryanodine decreased everolimus-induced phosphorylation of PKCα and MLC, and barrier disruption in HPMECs. Consistent with in vitro data, everolimus treatment caused a visible lung-vascular barrier dysfunction, including an increase in protein in BALF and lung capillary-endothelial permeability, which was significantly attenuated by pretreatment with an inhibitor of PKCα, MLCK, and ryanodine. This study shows that everolimus induced pulmonary endothelial hyper-permeability, at least partly, in an MLC phosphorylation-mediated EC contraction which is influenced in a Ca2+-dependent manner and can lead to lung injury through mTOR-independent mechanisms.

Rhotekin regulates axon regeneration through the talin-Vinculin-Vinexin axis in Caenorhabditis elegans.

Axon regeneration requires actomyosin interaction, which generates contractile force and pulls the regenerating axon forward. In Caenorhabditis elegans, TLN-1/talin promotes axon regeneration through multiple down-stream events. One is the activation of the PAT-3/integrin-RHO-1/RhoA GTPase-LET-502/ROCK (Rho-associated coiled-coil kinase)-regulatory non-muscle myosin light-chain (MLC) phosphorylation signaling pathway, which is dependent on the MLC scaffolding protein ALP-1/ALP-Enigma. The other is mediated by the F-actin-binding protein DEB-1/vinculin and is independent of the MLC phosphorylation pathway. In this study, we identified the svh-7/rtkn-1 gene, encoding a homolog of the RhoA-binding protein Rhotekin, as a regulator of axon regeneration in motor neurons. However, we found that RTKN-1 does not function in the RhoA-ROCK-MLC phosphorylation pathway in the regulation of axon regeneration. We show that RTKN-1 interacts with ALP-1 and the vinculin-binding protein SORB-1/vinexin, and that SORB-1 acts with DEB-1 to promote axon regeneration. Thus, RTKN-1 links the DEB-1-SORB-1 complex to ALP-1 and physically connects phosphorylated MLC on ALP-1 to the actin cytoskeleton. These results suggest that TLN-1 signaling pathways coordinate MLC phosphorylation and recruitment of phosphorylated MLC to the actin cytoskeleton during axon regeneration.

LTBP1 promotes the progression of triple negative breast cancer via activating the RhoA/ROCK signaling pathway

&lt;p class="MsoNormal" style="text-align: justify;"&gt;&lt;span lang="EN-US"&gt;The latent transforming growth factor-beta (TGF-&amp;beta;) binding protein 1 (LTBP1) has been implicated in various cellular processes, but its role in triple-negative breast cancer (TNBC) remains unclear. In this study, we investigated the impact of LTBP1 on TNBC progression and its underlying mechanisms. Analysis of online datasets revealed elevated LTBP1 mRNA expression in breast cancer tissues compared to normal adjacent tissues. Kaplan-Meier Plotter analysis indicated that high LTBP1 expression was negatively correlated with relapse-free survival (RFS), distant-metastasis free survival (DMFS), and overall survival (OS) of breast cancer patients. Additionally, LTBP1 mRNA levels were associated with chemotherapy resistance. Functional assays in TNBC cells demonstrated that LTBP1 knockdown suppressed cell proliferation, induced apoptosis, and attenuated migration and invasion. In vivo studies confirmed that LTBP1 knockdown inhibited tumor growth in a xenograft mouse model. Mechanistically, LTBP1 positively correlated with genes involved in signaling regulation and organelle organization, with significant associations to GTPase binding and the RhoA/ROCK pathway. LTBP1 knockdown reduced RhoA activity and phosphorylation of Myosin Light Chain 2 (MLC2), suggesting inhibition of the RhoA/ROCK signaling pathway. Moreover, activation of the RhoA/ROCK pathway partially rescued the effects of LTBP1 knockdown on TNBC cell proliferation, apoptosis, migration, and invasion. In conclusion, our findings suggest that LTBP1 promotes TNBC progression through activation of the RhoA/ROCK signaling pathway, highlighting its potential as a therapeutic target for TNBC.&lt;/span&gt;&lt;/p&gt;

Growth prolongation of human induced pluripotent stem cell aggregate in three-dimensional suspension culture system by addition of botulinum hemagglutinin

Human induced pluripotent stem cells (hiPSCs) can be used in regenerative therapy as an irresistible cell source, and so the development of scalable production of hiPSCs for three-dimensional (3D) suspension culture is required. In this study, we established a simple culture strategy for improving hiPSC aggregate growth using botulinum hemagglutinin (HA), which disrupts cell-cell adhesion mediated by E-cadherin. When HA was added to the suspension culture of hiPSC aggregates, E-cadherin-mediated cell-cell adhesion was temporarily disrupted within 24h, but then recovered. Phosphorylated myosin light chain, a contractile force marker, was also recovered at the periphery of hiPSC aggregates. The cell aggregates were suppressed the formation of collagen type I shell-like structures at the periphery by HA and collagen type I was homogenously distributed within the cell aggregates. In addition, these cell aggregates retained the proliferation marker Ki-67 throughout the cell aggregates. The apparent specific growth rate with HA addition was maintained continuously throughout the culture, and the final cell density was 1.7-fold higher than that in the control culture. These cells retained high expression levels of pluripotency markers. These observations indicated that relaxation of cell-cell adhesions by HA addition induced rearrangement of the mechanical tensions generated by actomyosin in hiPSC aggregates and suppression of collagen type I shell-like structure formation. These results suggest that this simple and readily culture strategy is a potentially useful tool for improving the scalable production of hiPSCs for 3D suspension cultures.

Vascular endothelial growth factor induces the migration of human airway smooth muscle cells by activating the RhoA/ROCK pathway

BackgroundAirway remodeling due to increased airway smooth muscle cell (ASMC) mass, likely due to enhanced proliferation, hypertrophy, and migration, has been proven to be highly correlated with decreased lung function in asthma patients. Vascular endothelial growth factor (VEGF) mediates vascular and extravascular remodeling and inflammation and has been proven to be involved in the progression of asthma. Previous studies have focused on the effects of VEGF on ASMC proliferation, but few researchers have focused on the effects of VEGF on human ASMC migration. The purpose of this study was to explore the effect of VEGF on the migration of ASMCs and its related signaling pathway mechanism to provide evidence for the treatment of airway remodeling.MethodsWe examined the effects of VEGF induction on ASMC migration and explored the mechanisms involved in ASMC migration.ResultsWe found by wound healing and Transwell assays that VEGF promoted ASMC migration. Through the Cell Counting Kit-8 (CCK-8) experiment, we found that VEGF had no significant effect on the proliferation of ASMCs, which excluded the involvement of cell proliferation in the process of wound healing. Moreover, a cellular immunofluorescence assay showed that VEGF promoted F-actin reorganization, and Western blotting showed that VEGF improved RhoA activation and myosin phosphatase targeting subunit-1 (MYPT1) and myosin light chain (MLC) phosphorylation in ASMCs. Treatment with the ROCK inhibitor Y27632 significantly attenuated the effects of VEGF on MYPT1/MLC activation and cell migration.ConclusionIn conclusion, the results suggest that the promigratory function of VEGF activates the RhoA/ROCK pathway, induces F-actin reorganization, improves the migration of ASMCs, and provides a better rationale for targeting the RhoA/ROCK pathway for therapeutic approaches in airway remodeling.

Endothelial Cell Calcium Influx Mediates Trauma-induced Endothelial Permeability.

We aimed to investigate if ex vivo plasma from injured patients causes endothelial calcium (Ca2+) influx as a mechanism of trauma-induced endothelial permeability. Endothelial permeability after trauma contributes to post-injury organ dysfunction. While the mechanisms remain unclear, emerging evidence suggests intracellular Ca2+ signaling may play a role. Ex vivo plasma from injured patients with "Low Injury/Low Shock" (injury severity score [ISS]<15, base excess [BE])≥-6mEq/L) and "High Injury/High Shock" (ISS≥15, BE<-6mEq/L) were used to treat endothelial cells. Experimental conditions included Ca2+ removal from the extracellular buffer, cyclopiazonic acid pre-treatment to deplete intracellular Ca2+ stores, and GSK2193874 pre-treatment to block the TRPV4 Ca2+ channel. Live cell fluorescence microscopy and ECIS were used to assess cytosolic Ca2+ increases and permeability, respectively. Western blot and live cell actin staining were used to assess myosin light chain (MLC) phosphorylation and actomyosin contraction. Compared to Low Injury/Low Shock plasma, High Injury/High Shock induced greater cytosolic Ca2+ increase. Cytosolic Ca2+ increase, MLC phosphorylation, and actin cytoskeletal contraction were lower without extracellular Ca2+ present. High Injury/High Shock plasma did not induce endothelial permeability without extracellular Ca2+ present. TRPV4 inhibition lowered trauma plasma-induced endothelial Ca2+ influx and permeability. This study illuminates a novel mechanism of post-injury endotheliopathy involving Ca2+ influx via the TRPV4 channel. TRPV4 inhibition mitigates trauma-induced endothelial permeability. Moreover, widespread endothelial Ca2+ influx may contribute to trauma-induced hypocalcemia. This study provides the mechanistic basis for the development of Ca2+-targeted therapies and interventions in the care of severely injured patients.

Interleukin 31 receptor α promotes smooth muscle cell contraction and airway hyperresponsiveness in asthma

Asthma is a chronic inflammatory airway disease characterized by airway hyperresponsiveness (AHR), inflammation, and goblet cell hyperplasia. Multiple cytokines, including IFNγ, IL-4, and IL-13 are associated with asthma; however, the mechanisms underlying the effects of these cytokines remain unclear. Here, we report a significant increase in the expression of IL-31RA, but not its cognate ligand IL-31, in mouse models of allergic asthma. In support of this, IFNγ, IL-4, and IL-13 upregulated IL-31RA but not IL-31 in both human and mice primary airway smooth muscle cells (ASMC) isolated from the airways of murine and human lungs. Importantly, the loss of IL-31RA attenuated AHR but had no effect on inflammation and goblet cell hyperplasia in mice challenged with allergens or treated with IL-13 or IFNγ. We show that IL-31RA functions as a positive regulator of muscarinic acetylcholine receptor 3 expression, augmenting calcium levels and myosin light chain phosphorylation in human and murine ASMC. These findings identify a role for IL-31RA in AHR that is distinct from airway inflammation and goblet cell hyperplasia in asthma.

Motility Assay to Probe the Calcium Sensitivity of Myosin and Regulated Thin Filaments.

Calcium-dependent activation of the thin filament mediated by the troponin-tropomyosin complex is key in the regulation of actin-myosin based muscle contraction. Perturbations to this system, either physiological (e.g., phosphorylation of myosin light chains) or pathological (e.g., mutations that cause familial cardiomyopathies), can alter calcium sensitivity and thus have important implications in human health and disease. The in vitro motility assay provides a quantitative and precise method to study the calcium sensitivity of the reconstituted myosin-thin filament motile system. Here we present a simple and robust protocol to perform calcium-dependent motility of β-cardiac myosin and regulated thin filaments. The experiment is done on a multichannel microfluidic slide requiring minimal amounts of proteins. A complete velocity vs. calcium concentration curve is produced from one experiment in under 1h.

A Dual-Specific Inhibitor of Rock/Aurk, RR-1752, for Primary Myelofibrosis

Myelofibrosis (MF) is a clonal myeloproliferative neoplasm (MPN) characterized by driver mutations in JAK2, CALR, and MPL resulting in constitutive activation of JAK-STAT signaling. Abnormalities in megakaryocyte (MK) numbers and morphology are a common feature of MF where abnormal MKs are associated with bone marrow fibrosis and pro-inflammatory cytokine release. Therapies that target constitutive JAK-STAT signaling and atypical megakaryocytes could provide clinical benefit for patients with MF. ROCK and Aurora kinase (AURK) are overexpressed in MPN and linked to dysregulated MKs of patients with MPN. We therefore tested the activity of RR-1752, a dual-specific inhibitor of ROCK and AURK, in preclinical models of MF. RR-1752 acted as an inhibitor of pSTAT3 in IL-2 stimulated human PBMC 1h post stimulation and significantly inhibited phosphorylated myosin light chain 2 (pMLC2) in two human MPN cell lines, HEL-92.1.7 and UKE-1, confirming an on-target action. RR-1752 inhibited colony formation by HEL-92.1.7 and UKE-1, (IC 50 = 25.2 nM and 54.6 nM respectively). RR-1752 also induced cell cycle arrest in HEL-92.1.7 and UKE-1 specifically at the G2/M checkpoint. RR-1752 was also tested in a hematopoietic colony formation assays of MF patient derived CD34 + cells. RR-1752 led to concentration specific inhibition of MF patient derived CD34 + cell colony formation between 100-190 nM demonstrating relevant activity against patient-derived MF samples (51% inhibition at 190 nM as compared to vehicle control). These data were in line with flow cytometrically determined cell viability data of MF CD34 + cells cultured in the presence of varying concentrations of RR-1752 in liquid culture. The in vivo activity of RR-1752, was examined using the human HEL- 92.1.7 cell line, homozygous for both JAK2 V617F and p53 M133K in a mouse xenograft model. The effects of RR-1752 alone and in combination with ruxolitinib were compared to single agent ruxolitinib. The administration of RR-1752, 25 mg/kg PO daily resulted in a significant (p&amp;lt;0.01) improvement in median survival (31 days) compared to ruxolitinib alone, 45 mg/kg PO daily (21 days). RR-1752 5.0 mg/kg PO QD plus ruxolitinib 45 mg/kg PO QD also resulted in a significant improvement in survival (p&amp;lt;0.05) compared to single agent ruxolitinib but was inferior to single agent RR-1752 at 25mg/kg. The demonstrated activity in MF patient derived CD34 + cells combined with the significant improvement in survival compared to the approved drug ruxolitinib in an aggressive, JAK2/p53 mutant MF xenograft model provides a compelling case for its evaluation as a therapeutic modality in MF patients. Dose optimization of RR-1752 alone and in combination with ruxolitinib in the HEL-92.1.7 IV dissemination model as well as testing in the hMPL-W515L-evoked myelofibrosis model is ongoing. Conventional treatments for MF have largely focused on symptom management but RR-1752 treatment could result not only in beneficial symptom improvement but also important disease modifying potential by inhibiting JAK-STAT signaling, cell cycle progression and targeting dysregulated MKs.

Role of protein kinase D1 in vasoconstriction and haemodynamics in rats

AimsProtein kinase D (PKD), once considered an effector of protein kinase C (PKC), now plays many pathophysiological roles in various tissues. However, little is known about role of PKD in vascular function. We investigated the role of PKD in contraction of rat aorta and human aortic smooth muscle cells (HASMCs) and in haemodynamics in rats. Methods and resultsIsometric tension of rat aortic was measured to examine norepinephrine-induced contraction in the presence of PKD, PKC and Rho-kinase inhibitors. Phosphorylation of PKD1, myosin targeting subunit-1 (MYPT1), myosin light chain (MLC), CPI-17 and heat-shock protein 27 (HSP27), and actin polymerization were measured in the aorta. Phosphorylation of MYPT1 and MLC was also measured in HASMCs knocked down with specific siRNAs of PKD 1, 2 and 3. Intracellular calcium concentrations and cell shortening were measured in HASMCs.Norepinephrine-induced aortic contraction was accompanied by increased phosphorylation of PKD1, MYPT1 and MLC and actin polymerization, all of which were attenuated with PKD inhibitor CRT0066101. PKD1 phosphorylation was not inhibited by PKC inhibitor, chelerythrine or Rho kinase inhibitor, fasudil. In HASMCs, the phosphorylation of MYPT1 and MLC was attenuated by PKD1, but not PKD2, 3 knockdown. In HASMCs, CRT0066101 inhibited norepinephrine-induced cell shortening without affecting calcium concentration. Administration of CRT0066101 decreased systemic vascular resistance and blood pressure without affecting cardiac output in rats. ConclusionsPKD1 may play roles in aorta contraction and haemodynamics via phosphorylation of MYPT1 and actin polymerization in a calcium-independent manner.

Inhibition of UTX/KDM6A improves recovery of spinal cord injury by attenuating BSCB permeability and macrophage infiltration through the MLCK/p-MLC pathway

Spinal cord injury (SCI) can prompt an immediate disruption to the blood–spinal cord barrier (BSCB). Restoring the integrity of this barrier is vital for the recovery of neurological function post-SCI. The UTX protein, a histone demethylase, has been shown in previous research to promote vascular regeneration and neurological recovery in mice with SCI. However, it is unclear whether UTX knockout could facilitate the recovery of the BSCB by reducing its permeability. In this study, we systematically studied BSCB disruption and permeability at different time points after SCI and found that conditional UTX deletion in endothelial cells (ECs) can reduce BSCB permeability, decrease inflammatory cell infiltration and ROS production, and improve neurological function recovery after SCI. Subsequently, we used RNA sequencing and ChIP-qPCR to confirm that conditional UTX knockout in ECs can down-regulate expression of myosin light chain kinase (MLCK), which specifically mediates myosin light chain (MLC) phosphorylation and is involved in actin contraction, cell retraction, and tight junctions (TJs) protein integrity. Moreover, we found that MLCK overexpression can increase the ratio of p-MLC/MLC, further break TJs, and exacerbate BSCB deterioration. Overall, our findings indicate that UTX knockout could inhibit the MLCK/p-MLC pathway, resulting in decreased BSCB permeability, and ultimately promoting neurological recovery in mice. These results suggest that UTX is a promising new target for treating SCI.Graphical

Cardiac-specific deletion of myosin phosphatase targeting subunit 2 alleviates cardiac fibrosis in mineralocorticoid receptor-related hypertension

Abstract Introduction Myosin phosphatase targeting subunit 2 (MYPT2) is a crucial subunit of cardiac myosin light chain (MLC) phosphatase. The phosphorylation of MLC in the ventricle plays a pivotal role in cardiac hypertrophy and function. Our previous study demonstrated that overexpression of MYPT2 activated MLC phosphatase leading to cardiac dysfunction. Mineralocorticoid receptor (MR)-related hypertension is associated with extensive cardiac fibrosis. It remains unknown whether MYPT2 may play a role in the development of cardiac fibrosis in MR-related hypertension. Purpose Our purpose is to investigate the effect of MYPT2 on cardiac fibrosis in MR-related hypertension. Methods After the knockdown of MYPT2 using MYPT2-siRNA, HL-1 cells (murine cardiomyocytes) were incubated with aldosterone (ALDO) for 24h. Cardiac-­specific MYPT2 knockout (c-MYPT2-/-) mice were generated using the Cre-lox system (αMHC-­Cre; MYPT2f/f). MR-related hypertension mice were induced in c-MYPT2-/- and wild-type (MYPT2+/+) mice with the subcutanouse infusion of ALDO and 8% NaCl food for 4 weeks after uninephrectomy. Systolic blood pressure (SBP) was measured by tail cuffs every week. WB, qPCR, cardiac echo, and histological examinations were performed. Results In HL-1 cells, ALDO increased the expression of connective tissue growth factor (CTGF), MYPT2, and the catalytic subunit of the type-1 phosphatase δ isoform (PP1cδ) in a concentration-dependent manner. MYPT2 protein levels significantly decreased by 80% in HL-1 cells transfected with MYPT2 siRNA compared with cells transfected with unspecific siRNA. Knockdown of MYPT2 significantly decreased the protein level of CTGF. In the mice model, the MYPT2 expression in the heart from MYPT2-/- mice was decreased to less than 30% compared with MYPT2+/+ mice. Heart rate, blood pressure, and cardiac systolic function were normal in c-MYPT2-/- mice. PP1cδ was decreased in c-MYPT2-/- mice compared with MYPT2+/+ mice. The expression of cardiac MLC kinase was not changed. The level of phosphorylation of MLC in c-MYPT2-/- mice was significantly higher than MYPT2+/+. Blood pressure elevation and left ventricular hypertrophy were observed in both MR-related hypertension mice. No significant difference in heart size and the nuclear localization of MR in cardiomyocytes. However, ejection fraction and fractional shortening in echocardiography were higher in c-MYPT2-/- than in MYPT2+/+ in MR-related hypertension mice. Histopathological examinations revealed the degree of fibrosis in c-MYPT2-/- mice was lower than in MYPT2+/+ mice with the decreased expression of CTGF. Conclusions Cardiac-specific deletion of MYPT2 resulted in a decrease of MLC phosphatase and an increase of phosphorylation in MLC in vivo. MYPT2 deletion can inhibit cardiac fibrosis in a MR-related hypertension model.

Abstract 12167: Cardiac-Specific Knockout of Myosin Phosphatase Targeting Subunit 2 Prevents Cardiac Fibrosis in a Connective Tissue Growth Factor-Dependent Manner in Mineralocorticoid Receptor-Related Hypertension Mice

Introduction: Myosin phosphatase targeting subunit 2 (MYPT2) is an important subunit of cardiac myosin light chain phosphatase (MLCP), which plays a crucial role in regulating the phosphorylation of MLC (p-MLC). Recent research has shown that cardiac MLCP plays an important role in cardiac fibrosis as a target of Rho kinase and protein kinase G. However, it is unclear how the loss of MYPT2 affects cardiac function and fibrosis. Methods: After the knockdown of MYPT2, HL-1 cells (murine cardiomyocytes) were incubated with aldosterone (ALDO) for 24h. Cardiac specific MYPT2 knockout (c-MYPT2 -/- ) mice were generated using the Cre lox system (αMHCMerCreMer; MYPT2 f/f ). Mineralocorticoid receptor (MR)-related hypertension mice were induced by the subcutaneous infusion of ALDO and 8% NaCl food for 4 weeks after uninephrectomy. Results: In HL-1 cells, ALDO increased connective tissue growth factor (CTGF) and MYPT2 and decreased the p-MLC in a dose-dependent manner. Knockdown of MYPT2 decreased CTGF. In mice model, the MYPT2 expression in the heart from MYPT2 -/- mice was decreased to less than 30% compared with MYPT2 +/+ mice. Heart rate, blood pressure, and cardiac systolic function were normal in c-MYPT2 -/- mice. Type 1 phosphatase catalytic subunit β was decreased and p-MLC was increased in c-MYPT2 -/- mice. Blood pressure elevation and left ventricular hypertrophy were observed in both MR-related hypertension mice, while no difference in heart size and the nuclear localization of MR in cardiomyocytes. However, ejection fraction and fractional shortening in echocardiography were higher in c-MYPT2 -/- than in MYPT2 +/+ in MR-related hypertension mice. After treatment of ALDO for 28 days, both global radial and longitudinal strain (GRS and DLS) were reduced in both c-MYPT2 -/- and MYPT2 +/+ mice, but the reduction in systolic and diastolic GRS and GLS strain rates were prevented in c-MYPT2 -/- mice compared with MYPT2 +/+ mice. Histopathology revealed fibrosis degree in c-MYPT2 -/- mice was lower than MYPT2 +/+ mice with decreased CTGF and increased p-MLC. Conclusions: Cardiac-specific deletion of MYPT2 resulted in a decrease of MLCP and an increase of p-MLC. MYPT2 deletion can prevent cardiac fibrosis and dysfunction in a MR-related hypertension model.

Anemoside B4 ameliorates dextran sulfate sodium (DSS)-induced colitis through inhibiting NLRP3 inflammasome and modulating gut microbiota

Ulcerative colitis (UC) has been recognized as a chronic and relapsing inflammatory disease of the gastrointestinal tract. Clinically, aminosalicylates, immunosuppressants and biological agents are commonly used to treat UC at different stages of the disease. However, these drugs often have side effects. Here, we investigated the anti-UC activity of Anemoside B4 (AB4) in mice with dextran sulfate sodium (DSS) induced colitis. Colon tissues, serum, and colonic contents were collected for assessment of intestinal barrier function, inflammatory cytokines production and microenvironment of intestinal microbiota. Results showed that AB4 alleviated colon shortening, weight lossing and histopathological damage in DSS-induced mice. In addition, we demonstrated both in vivo and in vitro that AB4 remarkably ameliorated colonic inflammation through suppressing NLRP3 pathway. Moreover, AB4 strengthened the intestinal epithelial barrier by regulating myosin light chain kinase (MLCK)-phosphorylated myosin light chain 2 (pMLC2) signaling pathway. Furthermore, we performed 16 S rRNA gene sequencing and fecal microbiome transplantation (FMT) experiments to demonstrate that AB4 alleviated colitis through regulating dysbiosis of intestinal microbiota. These results revealed that AB4 effectively ameliorate experimental UC mainly through regulating MLCK/pMLC2 pathway, NLRP3 pathway and dysbiosis of microbiota, provided new insights into the development of novel anti-UC drugs.

The protein kinase A signaling pathway mediates the effect of electroacupuncture on excessive contraction of the bladder detrusor in a rat model of neurogenic bladder.

Neurogenic bladder (NB) is a form of neurological bladder dysfunction characterized by excessive contraction of the bladder detrusor. Protein kinase A (PKA) signaling is involved in the contraction of the detrusor muscle. To investigate whether PKA signaling mediates the effect of electroacupuncture (EA) on the excessive contraction of the bladder detrusor in NB. Sixty rats were randomly divided into control, sham, NB, NB + EA, and NB + EA + H89 (a PKA receptor antagonist) groups. The modified Hassan Shaker spinal cord transection method was used to generate a NB model. After EA intervention for one week, urodynamic tests were used to evaluate bladder function, hematoxylin and eosin staining was conducted to assess morphological changes, enzyme-linked immunosorbent assay (ELISA) was performed to measure the concentration of PKA, and Western blotting was conducted to measure the protein levels of phosphorylated myosin light chain kinase (p-MLCK)/p-MLC. The results showed that NB resulted in morphological disruption, impairment of urodynamics, and decreases in the concentration of PKA and the protein levels of p-MLCK/p-MLC. EA reversed the changes induced by NB dysfunction. However, the improvement in urodynamics and the increases in the concentration of PKA and the protein levels of p-MLCK/p-MLC were inhibited by H89. Our findings indicate that the PKA signaling pathway mediates the beneficial effect of EA on excessive contraction of the bladder detrusor in a rat model of NB.