Ionic mechanisms of desflurane on prolongation of action potential duration in rat ventricular myocytes

Purpose

Despite the fact that desflurane prolongs the QTC interval in humans, little is known about the mechanisms that underlie these actions. We investigated the effects of desflurane on action potential (AP) duration and underlying electrophysiological mechanisms in rat ventricular myocytes.

Materials and Methods

Rat ventricular myocytes were enzymatically isolated and studied at room temperature. AP was measured using a current clamp technique. The effects of 6% (0.78 mM) and 12% (1.23 mM) desflurane on transient outward K⁺ current (I_to), sustained outward current (I_sus), inward rectifier K⁺ current (I_KI), and L-type Ca²⁺ current were determined using a whole cell voltage clamp.

Results

Desflurane prolonged AP duration, while the amplitude and resting membrane potential remained unchanged. Desflurane at 0.78 mM and 1.23 mM significantly reduced the peak I_to by 20±8% and 32±7%, respectively, at +60 mV. Desflurane (1.23 mM) shifted the steady-state inactivation curve in a hyperpolarizing direction and accelerated inactivation of the current. While desflurane (1.23 mM) had no effects on I_sus and I_KI, it reduced the L-type Ca²⁺ current by 40±6% (p<0.05).

Conclusion

Clinically relevant concentrations of desflurane appear to prolong AP duration by suppressing I_to in rat ventricular myocytes.     

Prevalence of the CTNNB1 mutation genotype in surgically resected fibromatosis of the breast

Kim T, Jung E A, Song J Y, Roh J H, Choi J S, Kwon J E, Kang S Y, Cho E Y, Shin J H, Nam S‐J, Yang J H & Choi Y‐L
(2012) Histopathology  60, 347–356
Prevalence of the CTNNB1 mutation genotype in surgically resected fibromatosis of the breast Aims: To investigate CTNNB1 mutation and β‐catenin expression in resected breast fibromatosis and to identify potential molecular markers of fibromatosis of the breast. Methods and results: We selected 12 patients with fibromatosis of the breast who underwent surgical resection and were confirmed by histological examination. Ultrasonography findings for 10 patients were reviewed and only two cases were suspicious for fibromatosis on imaging. On core needle biopsy for pre‐operative diagnoses, only three cases were histologically suspicious for fibromatosis. Mutations in exon 3 of CTNNB1 were detected by direct DNA sequencing in nine (75.0%) cases: all were c.121G>A (p.T41A), which was much more frequent in breast fibromatoses than in other soft tissue lesions. Nuclear β‐catenin expression was observed in all cases and the level of expression was higher in cases with mutation. In eight of nine cases, the matched biopsy specimen showed the same CTNNB1 mutation status as the pre‐operative specimen. Conclusions: In the majority of cases, clinical presentation and breast imaging are highly suspicious for carcinoma. Definitive pre‐operative pathological diagnosis by core needle biopsy is difficult. CTNNB1 mutation and nuclear β‐catenin expression are frequently detected in sporadic breast fibromatoses, suggesting their potential as a useful tool to distinguish breast fibromatoses from other neoplasms.     

NOD1 and NOD2 stimulation triggers innate immune responses of human periodontal ligament cells

Nod-like receptors (NLRs) are cytosolic sensors for microbial molecules. Νucleotide-binding oligomerization domain (NOD)1 and NOD2 recognize the peptidoglycan derivatives, meso-diaminopimelic acid (meso-DAP) and muramyl dipeptide (MDP), respectively, and trigger host innate immune responses. In the present study, we examined the function of NOD1 and NOD2 on innate immune responses in human periodontal ligament (PDL) cells. The gene expression of NOD1 and NOD2 was examined by RT-PCR. IL-6 and IL-8 production in culture supernatants was measured by ELISA. Western blot analysis was performed to determine the activation of NF-κB and MAPK in response to Tri-DAP and MDP. The genes of NOD1 and NOD2 appeared to be expressed in PDL cells. Although the levels of NOD2 expression were weak in intact cells, MDP stimulation increased the gene expression of NOD2 in PDL cells. Tri-DAP and MDP led to the production of IL-6 and IL-8 and the activation of NF-κB and MAPK in PDL cells. Toll-like receptor (TLR) stimulation led to increased gene expression of NOD1 and NOD2 in PDL cells. Pam3CSK4 (a TLR2 agonist) and IFN-γ synergized with Tri-DAP and MDP to produce IL-8 and IL-6 in PDL cells. Our results indicate that NOD1 and NOD2 are functionally expressed in human PDL cells and can trigger innate immune responses.     

The effect of oxidation on the degradation of photocrosslinkable alginate hydrogels

Recently, we reported on a new photocrosslinkable alginate-based hydrogel, which has controllable physical and cell adhesive properties. The macromer solution containing cells can be injected in a minimally invasive manner into a defect site and crosslinked while maintaining high cell viability. The number of hydrolyzable ester bonds in the formed crosslinks may be controlled by altering the degree of methacrylation on the alginate polymer backbone. However, the degradation rate of the hydrogels has been found to be slower in vivo than in vitro. The purpose of this study was to develop photocrosslinked alginate hydrogels with an increased range of biodegradation rates for more rapid in vivo biodegradation in regenerative medicine and bioactive factor delivery applications. Therefore, we oxidized alginate prior to methacrylation to change the uronate residue conformations to an open-chain adduct, which makes it more vulnerable to hydrolysis. Here, we demonstrate that the swelling behavior, degradation profiles, and storage moduli of photocrosslinked hydrogels formed from oxidized, methacrylated alginates (OMAs) are tunable by varying the degree of alginate oxidation. The OMA macromers and photocrosslinked OMA hydrogels exhibited cytocompatibility when cultured with human bone marrow-derived mesenchymal stem cells (hBMMSCs). In addition, hMSCs derived from bone marrow or adipose tissue photoencapsulated within these hydrogels remained viable, and their proliferation rate was a function of alginate oxidation level and initial hydrogel weight fraction. Oxidation permits a wider range of photocrosslinked OMA hydrogels physical properties, which may enhance these therapeutic materials' utility in tissue engineering and other biomedical applications.     

Adoptive transfer of all-trans-retinal-induced regulatory T cells ameliorates experimental autoimmune arthritis in an interferon-gamma knockout model

Maintaining an appropriate balance between subsets of CD4(+) helper T cells and T regulatory cells (Tregs) is a critical process in immune homeostasis and a protective mechanism against autoimmunity and inflammation. To identify the role of vitamin A-related compounds, we investigated the regulation of interleukin (IL)-17-producing helper T cells (Th17 cells) and Tregs treated with all-trans-retinal (retinal). CD4(+)T cells or total cells from the spleens of C57BL/6 mice were stimulated under Treg-polarizing (anti-CD3/CD28 and TGF-β) or Th17-polarizing (anti-CD3/CD28, TGF-β, and IL-6) conditions in the presence or absence of retinal. To analyze their suppressive abilities, retinal-induced Tregs or TGF-β-induced Tregs were co-cultured with responder T cells. Collagen-induced arthritis (CIA) was established in interferon (IFN)-γ knockout mice. On day 13, retinal-induced Tregs were adoptively transferred to mice with established CIA after second immunizations. Compared with TGF-β-induced Treg cells, retinal-induced Tregs showed increased Foxp3 expression and mediated stronger suppressive activity. Under Th17-polarizing conditions, retinal inhibited the production of IL-17 and increased the expression of Foxp3.Retinal-induced Tregs showed therapeutic effects in IFN-γ knockout CIA mice. Thus, we demonstrated that retinal reciprocally regulates Foxp3(+) Tregs and Th17 cells. These findings suggest that retinal, a vitamin A metabolite, can regulate the balance between pro- and anti-inflammatory immunity. A better understanding of the manipulation of Foxp3 and Tregs may enable the application of this tremendous therapeutic potential in various autoimmune diseases.     

AMPK activation reduces vascular permeability and airway inflammation by regulating HIF/VEGFA pathway in a murine model of toluene diisocyanate-induced asthma

Background

Occupational asthma is characterized by airway inflammation and hyperresponsiveness associated with increased vascular permeability. AMP-activated protein kinase (AMPK) has been suggested to be a novel signaling molecule modulating inflammatory responses.

Objective

We sought to evaluate the involvement of AMPK in pathogenesis of occupational asthma and more specifically investigate the effect and molecular mechanisms of AMPK activation in regulating vascular permeability.

Methods

The mechanisms of action and therapeutic potential of an AMPK activator, 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside (AICAR) were tested in a murine model of toluene diisocyanate (TDI)-induced asthma.

Results

AICAR attenuated airway inflammation and hyperresponsiveness increased by TDI inhalation. Moreover, TDI-induced increases in levels of hypoxia-inducible factor (HIF)-1α, HIF-2α, vascular endothelial growth factor A (VEGFA), and plasma exudation were substantially decreased by treatment with AICAR. Our results also showed that VEGFA expression was remarkably reduced by inhibition of HIF-1α and HIF-2α with 2-methoxyestradiol (2ME2) and that an inhibitor of VEGFA activity, CBO-P11 as well as 2ME2 significantly suppressed vascular permeability, airway infiltration of inflammatory cells, and airway hyperresponsiveness induced by TDI. In addition, AICAR reduced reactive oxygen species (ROS) generation and levels of malondialdehyde and T-helper type 2 cytokines (IL-4, IL-5, and IL-13), while this agent enhanced expression of an anti-inflammatory cytokine, IL-10.

Conclusions

These results suggest that AMPK activation ameliorates airway inflammatory responses by reducing vascular permeability via HIF/VEGFA pathway as well as by inhibiting ROS production and thus may be a possible therapeutic strategy for TDI-induced asthma and other airway inflammatory diseases.     

Biomechanical analysis of the effects of medial meniscectomy on degenerative osteoarthritis

To investigate the effects of meniscectomy on degenerative osteoarthritis, a three-dimensional (3D) finite element (FE) model of the human lower limb is constructed from a combination of magnetic resonance (MR) images and computed tomographic (CT) images that can provide anatomically suitable boundary conditions for a knee joint. Four cases, i.e., the intact meniscus, and the partial, sub-total, and total meniscectomy of the medial meniscus are modeled and simulated. We consider that the cartilage-to-cartilage contact area and the peak contact pressure in the meniscus may be significant parameters in evaluating degenerative osteoarthritis. Partial meniscectomy can be regarded as a better treatment than sub-total/total meniscectomy, and a high possibility of degenerative osteoarthritis is anticipated after total meniscectomy. Moreover, medial meniscectomy has the potential to bring about degenerative osteoarthritis in both the medial compartment and the lateral compartment of a knee joint.     

A study of the PEMT gene in schizophrenia

The phospholipid hypothesis of schizophrenia is becoming popular because of the findings from the niacin flush test, the treatment with polyunsaturated fatty acids (PUFAs), biochemical studies for the phospholipid metabolism pathway and genetic studies of phospholipase A2. The present study attempted to investigate the gene coding for phosphatidylethanolamine N-methyltransferase (PEMT), which is an important enzyme for the synthesis of membrane phospholipids. We recruited 271 Chinese parent-offspring trios of Han descent and detected 3 single nucleotide polymorphisms (SNPs) at the PEMT locus. The transmission disequilibrium test (TDT) showed allelic association for rs464396 (X2=9.4, P=0.002), but not for the other two. The 2-SNP haplotype analysis showed haplotypic association for both the rs936108-rs464396 haplotypes (X2=25.7, d.f.=3, P=0.00001) and the rs464396-rs4244593 haplotypes (X2=17.3, d.f.=3, P=0.0006). The 3-SNP haplotype analysis also showed a haplotypic association (X2=24.4, d.f.=7, P=0.0006). The present results suggest that the PEMT gene may contribute to the etiology of schizophrenia.