Rho kinase and protein kinase C involvement in vascular smooth muscle myofilament calcium sensitization in arteries from diabetic rats

Background and purpose:

Diabetes mellitus (DM) causes multiple dysfunctions including circulatory disorders such as cardiomyopathy, angiopathy, atherosclerosis and arterial hypertension. Rho kinase (ROCK) and protein kinase C (PKC) regulate vascular smooth muscle (VSM) Ca²⁺ sensitivity, thus enhancing VSM contraction, and up-regulation of both enzymes in DM is well known. We postulated that in DM, Ca²⁺ sensitization occurs in diabetic arteries due to increased ROCK and/or PKC activity.

Experimental approach:

Rats were rendered hyperglycaemic by i.p. injection of streptozotocin. Age-matched control tissues were used for comparison. Contractile responses to phenylephrine (Phe) and different Ca²⁺ concentrations were recorded, respectively, from intact and chemically permeabilized vascular rings from aorta, tail and mesenteric arteries.

Key results:

Diabetic tail and mesenteric arteries demonstrated markedly enhanced sensitivity to Phe while these changes were not observed in aorta. The ROCK inhibitor HA1077, but not the PKC inhibitor chelerythrine, caused significant reduction in sensitivity to agonist in diabetic vessels. Similar changes were observed for myofilament Ca²⁺ sensitivity, which was again enhanced in DM in tail and mesenteric arteries, but not in aorta, and could be reduced by both the ROCK and PKC blockers.

Conclusions and implications:

We conclude that in DM enhanced myofilament Ca²⁺ sensitivity is mainly manifested in muscular-type blood vessels and thus likely to contribute to the development of hypertension. Both PKC and, in particular, ROCK are involved in this phenomenon. This highlights their potential usefulness as drug targets in the pharmacological management of DM-associated vascular dysfunction.     

Surface antigenic determinants on human pluripotent and unipotent hematopoietic progenitor cells

RFB-1 is a monoclonal antibody previously shown to react with granulocyte-monocyte progenitors (CFU-GM) and immature lymphoid cells in human bone marrow. RFB-HLA-DR is a monoclonal antibody that reacts with HLA-DR (la-like) antigens. The present study shows that the bone marrow subset reactive with both RFB-1 and RFB-HLA-DR contains all the cells that give rise to mixed hematopoietic colonies (derived from CFU- GEMM; a pluripotent human progenitor cell) as well as to megakaryocytic (megakaryocyte-CFU-derived) and erythropoietic (derived from erythroid burst-forming units, BFU-E) colonies, as shown by fluorescence- activated cell sorting and complement-mediated cytotoxicity. These results indicate that CFU-GEMM, BFU-E, and megakaryocyte-CFU express RFB-1 and la-like antigens. RFB-1 antigen is also expressed on erythroid colony-forming units (CFU-E). RFB-1 and RFB-HLA-DR are useful reagents in the study of hematopoietic stem cells.     

A role for extracellular Na+ in the channel gating of native and recombinant kainate receptors

Ionotropic glutamate receptors of the kainate and AMPA subtypes share a number of structural features, both topographical and in terms of stoichiometry. In addition, AMPA and kainate receptors share similar pharmacological and biophysical properties in that they are activated by common agonists and display rapid activation and desensitization characteristics. However, we show here that in contrast to AMPA receptor-mediated responses (native or recombinant GluR3 receptor), the response of native and recombinant (GluR6) kainate receptors to glutamate was drastically reduced in the absence of extracellular Na+ (i.e., when replaced by Cs+). Removal of Na+ increases the rate of desensitization, indicating that external Na+ modulates channel gating. Whereas the size of the substituting cation is important in mimicking the action of Na+ (Li+>K+>Cs+), modulation was voltage independent. These results indicate the existence of different gating mechanisms for AMPA and kainate receptors. By using chimeric AMPA-kainate receptors derived from GluR3 and GluR6, we have identified a key residue in the S2 segment of GluR6 (M770) that is largely responsible for the sensitivity of the receptor to external Na+. Thus, these results show the existence of a specific kainate receptor gating mechanism that requires external Na+ to be operative.     

Pathogenesis of subacute cutaneous lupus erythematosus

Subacute cutaneous lupus erythematosus (SCLE) is a photosensitive form of lupus‐specific skin lesion that is strongly associated with the presence of anti‐Ro/SSA autoantibody. The pathogenesis of SCLE includes genetic, environmental and immunologic factors. Recent studies provide strong evidence for the involvement of innate and cell‐mediated immunity, underlying the important role of plasmacytoid dendritic cells, interferon‐α and antibody‐dependent cell cytotoxicity. In addition, a variety of cytokines, chemokines and adhesion molecules have been found to participate in the expansion phase of the autoimmune effector mechanisms. This article summarizes the recent immunological findings and reviews the current mechanisms which are implied in the development of the disease.     

Keratosis lichenoides chronica and eruptive keratoacanthoma-like lesions in a patient with multiple myeloma

We describe a 72-year-old woman with a 13-year history of a lichenoid dermatitis, who developed multiple, papular keratoacanthoma (KA)-like lesions and few crater-like nodules on the extremities over a period of 6 months before our observation. Her medical history also recorded multiple myeloma diagnosed a few years before. The long-standing dermatosis was diagnosed, clinically, as keratosis lichenoides chronica (KLC), although, histologically, a lichenoid tissue reaction pattern was not evident. On the other hand, histology from papular and nodular lesions of recent onset was consistent with a possible early phase of KA and spinocellular carcinoma, respectively. Oral acitretin induced regression of KA-like lesions and improvement of KLC but had no effects on crater-like nodules, which required surgical excision. KLC is a chronic disorder of keratinization characterized by lichenoid hyperkeratotic papules arranged in a linear pattern, erythematosquamous plaques and seborrhoea-like dermatitis. We emphasize in our case the association between KLC and multiple possible KAs, never previously reported, and speculate that these two rare conditions may represent here a 'continuum' from a pathogenetic point of view.     

Letter to the editor about “Effects of fruit and vegetables on metabolic syndrome: a systematic review and meta-analysis of randomized controlled trials” by Shin JY,Kim JY,Kang HT,Han KH,Shim JY published online in 2015 May 6

The letter to the editor presents methodological issues about the search strategy, adequate reporting of meta-analysis, and statistical details of the referred article.     

The relationship between the hemorrhagic and antithrombotic properties of low molecular weight heparin in rabbits

We have compared the hemorrhagic and antithrombotic effects of a low molecular weight (LMW) heparin fraction and standard heparin in rabbits. Similar LMW heparin fractions have antithrombotic effects when tested in animals, but their hemorrhagic effects relative to standard heparin have not been established. Standard porcine mucosal heparin (mol wt 15,000 daltons) was depolymerized by nitrous acid to a low molecular weight fraction (mol wt 4600 daltons). Using equal USP units, the standard and Dep LMW heparin were compared in vitro, ex vivo, and in vivo. In vitro, when diluted in rabbit plasma, the Dep LMW heparin at equivalent anti-Xa activity showed less prolongation of thrombin clotting times or activated partial thromboplastin times. Ex vivo, platelets from rabbits treated with the Dep LMW heparin showed less inhibition of collagen-induced aggregation. The relative hemorrhagic properties of the two heparins were compared in vivo in rabbits using a sensitive blood loss assay, and the antithrombotic properties were compared in a thrombin-induced venous stasis model. By using an optimal threshold heparin dose in each test system, it was possible to demonstrate that equal USP units of Dep LMW heparin caused less blood loss but showed greater antithrombotic activity than standard heparin.