Heat shock augments myosin phosphatase target-subunit phosphorylation

Antibacterial Films of Silver Nanoparticles Embedded into Carboxymethylcellulose/Chitosan Multilayers on Nanoporous Silicon: A Layer-by-Layer Assembly Approach Comparing Dip and Spin Coating

The design and engineering of antibacterial materials are key for preventing bacterial adherence and proliferation in biomedical and household instruments. Silver nanoparticles (AgNPs) and chitosan (CHI) are broad-spectrum antibacterial materials with different properties whose combined application is currently under optimization. This study proposes the formation of antibacterial films with AgNPs embedded in carboxymethylcellulose/chitosan multilayers by the layer-by-layer (LbL) method. The films were deposited onto nanoporous silicon (nPSi), an ideal platform for bioengineering applications due to its biocompatibility, biodegradability, and bioresorbability. We focused on two alternative multilayer deposition processes: cyclic dip coating (CDC) and cyclic spin coating (CSC). The physicochemical properties of the films were the subject of microscopic, microstructural, and surface-interface analyses. The antibacterial activity of each film was investigated against Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) bacteria strains as model microorganisms. According to the findings, the CDC technique produced multilayer films with higher antibacterial activity for both bacteria compared to the CSC method. Bacteria adhesion inhibition was observed from only three cycles. The developed AgNPs-multilayer composite film offers advantageous antibacterial properties for biomedical applications.

Impaired HSP70 Expression in the Aorta of Female Rats: A Novel Insight Into Sex-Specific Differences in Vascular Function

Heat-shock protein 70 (HSP70) contributes to cellular calcium (Ca2+) handling mechanisms during receptor-mediated vascular contraction. Interestingly, previous studies have independently reported sex-related differences in HSP70 expression and Ca2+ dynamics. Still, it is unknown if sex, as a variable, plays a role in the impact that HSP70 has upon vascular contraction. To narrow this gap, we investigated if differences exist in the expression levels of HSP70 in the aorta, and if targeting this protein contributes to sex disparity in vascular responses. We report that, compared with male animals, female rats present a reduction in the basal levels of HSP70. More compelling, we found that the blockade of HSP70 has a greater impact on phenylephrine-induced phasic and tonic vascular contraction in female animals. In fact, it seems that the inhibition of HSP70 significantly affects vascular Ca2+ handling mechanisms in females, which could be associated with the fact that these animals have impaired HSP70 expression. Corroborating this idea, we uncovered that the higher sensitivity of female rats to HSP70 inhibition does not involve an increase in NO-dependent vasodilation nor a decrease in vascular oxidative stress. In summary, our findings reveal a novel mechanism associated with sex-specific differences in vascular responses to α-1 adrenergic stimulation, which might contribute to unraveling the network of intertwined pathways conferring female protection to (cardio)vascular diseases.

An additional physiological role for HSP70: Assistance of vascular reactivity

AIMS

HSP70, a molecular chaperone, helps to maintain proteostasis. In muscle biology, however, evidence suggests HSP70 to have a more versatile range of functions, as genetic deletion of its inducible genes impairs Ca²⁺ handling, and consequently, cardiac and skeletal muscle contractility. Still, it is unknown whether HSP70 is involved in vascular reactivity, an intrinsic physiological mechanism of blood vessels. Therefore, we designed this study to test the hypothesis that proper vascular reactivity requires the assistance of HSP70.

MAIN METHODS

We performed functional studies in a wire-myograph using thoracic aorta isolated from male Sprague Dawley rats. Experiments were conducted with and without an HSP70 inhibitor as well as in heat-stressed vessels. The expression levels of HSP70 were evaluated with Western blotting. NO and ROS levels were assessed with fluorescence microscopy.

KEY FINDINGS

We report that blockade of HSP70 weakens contraction in response to phenylephrine (dose-response) in the aorta. Additionally, we demonstrated that inhibition of HSP70 affects the amplitude of the fast and of the slow components of the time-force curve. Corroborating these findings, we found that inhibition of HSP70, in vessels over-expressing this protein, partly rescues the contractile phenotype of aortic rings. Furthermore, we show that blockade of HSP70 facilitates relaxation in response to acetylcholine and clonidine without affecting the basal levels of NO and ROS.

SIGNIFICANCE

Our work introduces an additional physiological role for HSP70, the assistance of vascular reactivity, which highlights this protein as a new player in vascular physiology, and therefore, uncovers a promising research avenue for vascular diseases.

HMC05 attenuates vascular contraction through inhibition of RhoA/Rho-kinase signaling pathway

AIM OF THE STUDY

HMC05, an extract from eight different herbal mixtures, has been developed to treat cardiovascular disease. This extract has a vasorelaxant and anti-atherosclerotic action. We hypothesized that HMC05 attenuates vascular contraction through inhibition of the RhoA/Rho-kinase signaling pathway.

MATERIALS AND METHODS

Rat aortic ring preparations were mounted in organ baths and subjected to contraction and relaxation. Phosphorylation of 20 kDa myosin light chains (MLC(20)) and myosin phosphatase targeting subunit 1 (MYPT1) were examined by immunoblot. We also measured the amount of GTP RhoA as a marker for RhoA activation.

RESULTS

In endothelium-denuded aortic ring preparations, HMC05 relaxed vascular contraction induced by 6.0 mM NaF, 100 nM phenylephrine, 30 nM thromboxane A(2) agonist U46619 or 1.0 μM protein kinase C (PKC) activator phorbol-12,13-dibutyrate (PDBu) in a decreasing order. HMC05 relaxed aortic ring preparations precontracted with sodium fluoride (NaF) whether endothelium was intact or denuded. Pre-incubation with HMC05 for 30 min dose-dependently inhibited the NaF-induced contractile response. In vascular strips, HMC05 decreased the phosphorylation level of both MLC(20) and MYPT1(Thr855) induced by 6.0 mM NaF. Furthermore, HMC05 decreased the amount of GTP RhoA activated by NaF.

CONCLUSIONS

HMC05 attenuates vascular contraction through inhibition of the RhoA/Rho-kinase signaling pathway. HMC05 may be useful for the treatment and/or prevention of cardiovascular diseases associated with activation of RhoA/Rho-kinase signaling pathway.

Heat shock augments angiotensin II-induced vascular contraction through increased production of reactive oxygen species

A temporal increase in temperature triggers a series of stress responses and alters vascular smooth muscle (VSM) contraction induced by agonist stimulation. Here we examined the role of reactive oxygen species (ROS) in heat shock-dependent augmentation of angiotensin II (AngII)-induced VSM contraction. Endothelium-denuded rat aortic rings were treated with heat shock for 45 min at 42 degrees C and then subjected to assays for the production of force, ROS, and the expression of ROS-related enzymes. AngII-induced contraction was enhanced in heat shock-treated aorta. AngII-induced production of hydrogen peroxide and superoxide were elevated in response to the heat shock treatment. Pre-treatment with superoxide dismutases (SOD) mimetic and inhibitors for glutathione peroxidase and NADPH oxidase but not for xanthine oxidase eliminated an increase in the AngII-induced contraction in the heat shock-treated aorta. Heat shock increased the expression of p47phox, a cytosolic subunit of NADPH oxidase, but not Cu-Zn-SOD and Mn-SOD. In addition, heat shock increased contraction that was evoked by hydrogen peroxide and pyrogallol. These results suggest that heat shock causes an elevation of ROS as well as a sensitization of ROS signal resulting in an augmentation of VSM contraction in response to agonist.

Flavone Attenuates Vascular Contractions by Inhibiting RhoA/Rho Kinase Pathway

Our previous study demonstrated that flavone inhibits vascular contractions by decreasing the phosphorylation levelof the myosin phosphatase target subunit (MYPT1). In the present study, we hypothesized that flavone attenuates vascular contractions through the inhibition of the RhoA/Rho kinase pathway. Rat aortic rings were denuded of endothelium, mounted in organ baths, and contracted with either 30 nM U46619 (a thromboxane A2 analogue) or 8.0 mM NaF 30 min after pretreatment with either flavone (100 or 300 microM) or vehicle. We determined the phosphorylation level of the myosin light chain (MLC(20)), the myosin phophatase targeting subunit 1 (MYPT1) and the protein kinase C-potentiated inhibitory protein for heterotrimeric myosin light chain phophatase of 17-kDa (CPI17) by means of Western blot analysis. Flavone inhibited, not only vascular contractions induced by these contractors, but also the levels of MLC(20) phosphorylation. Furthermore, flavone inhibited the activation of RhoA which had been induced by either U46619 or NaF. Incubation with flavone attenuated U46619-or NaF-induced phosphorylation of MYPT1(Thr855) and CPI17(Thr38), the downstream effectors of Rho-kinase. In regards to the Ca(2+)-free solution, flavone inhibited the phosphorylation of MYPT1(Thr855) and CPI17(Thr38), as well as vascular contractions induced by U46619. These results indicate that flavone attenuates vascular contractions, at least in part, through the inhibition of the RhoA/Rho-kinase pathway.