Identification of small proline-rich repeat protein 3 as a novel atheroprotective factor that promotes adaptive Akt signaling in vascular smooth muscle cells.

OBJECTIVE: Atherosclerosis is the primary driver of cardiovascular disease, the leading cause of death worldwide. Identification of naturally occurring atheroprotective genes has become a major goal for the development of interventions that will limit atheroma progression and associated adverse events. To this end, we have identified small proline-rich repeat protein (SPRR3) as selectively upregulated in vascular smooth muscle cells (VSMCs) of atheroma-bearing arterial tissue versus healthy arterial tissue. In this study, we sought to determine the role of SPRR3 in atheroma pathophysiology. APPROACH AND RESULTS: We found that atheroprone apolipoprotein E-null mice lacking SPRR3 developed significantly greater atheroma burden. To determine the cellular driver(s) of this increase, we evaluated SPRR3-dependent changes in bone marrow-derived cells, endothelial cells, and VSMCs. Bone marrow transplant of SPRR3-expressing cells into SPRR3(-/-)apolipoprotein E-deficient recipients failed to rescue atheroma burden. Similarly, endothelial cells did not exhibit a response to SPRR3 loss. However, atheromas from SPRR3-deficient mice exhibited increased TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling)-positive VSMCs compared with control. Cell death in SPRR3-deficient VSMCs was significantly increased in vitro. Conversely, SPRR3-overexpressing VSMCs exhibited reduced apoptosis compared with control. We also observed a PI3K (phosphatidylinositol 3-kinase)/Akt-dependent positive association between SPRR3 expression and levels of active Akt in VSMCs. The survival advantage seen in SPRR3-overexpressing VSMCs was abrogated after the addition of a PI3K/Akt pathway inhibitor. CONCLUSIONS: These results indicate that SPRR3 protects the lesion from VSMC loss by promoting survival signaling in plaque VSMCs, thereby significantly decreasing atherosclerosis progression. As the first identified atheroma-specific VSMC prosurvival factor, SPRR3 represents a potential target for lesion-specific modulation of VSMC survival.

Atheromas feel the pressure: biomechanical stress and atherosclerosis.

Atherosclerosis, a chronic vascular disease, is the underlying cause of over half the deaths in the United States each year. Variations in local vascular hemodynamics predispose select sites in the vasculature to atherosclerosis, and the atherosclerotic lesions, in turn alter the biomechanical functioning of the local microenvironment, the consequences of which are not well understood on a molecular level. Further progress in the field of atherosclerosis will require an understanding of the relationship between biomechanics, the tissue microenvironment, and the cellular and molecular response to these factors. This review summarizes this field, particularly within the context of the vascular smooth muscle cell.

Regulation of the atheroma-enriched protein, SPRR3, in vascular smooth muscle cells through cyclic strain is dependent on integrin alpha1beta1/collagen interaction.

Atherosclerotic plaques express high levels of small proline-rich repeat protein (SPRR3), a previously characterized component of the cornified cell envelope of stratified epithelia, where it is believed to play a role in cellular adaptation to biomechanical stress. We investigated the physiological signals and underlying mechanism(s) that regulate atheroma-enriched SPRR3 expression in vascular smooth muscle cells (VSMCs). We showed that SPRR3 is expressed by VSMCs in both human and mouse atheromas. In cultured arterial VSMCs, mechanical cyclic strain, but neither shear stress nor lipid loading induced SPRR3 expression. Furthermore, this upregulation of SPRR3 expression was dependent on VSMC adherence to type I collagen. To link the mechanoregulation of SPRR3 to specific collagen/integrin interactions, we used blocking antibodies against either integrin alpha1 or alpha2 subunits and VSMCs from mice that lack specific collagen receptors. Our results showed a dependence on the alpha1beta1 integrin for SPRR3 expression induced by cyclic strain. Furthermore, we showed that integrin alpha1 but not alpha2 subunits were expressed on VSMCs within mouse lesions but not in normal arteries. Therefore, we identified the enrichment of the mechanical strain-regulated protein SPRR3 in VSMCs of both human and mouse atherosclerotic lesions whose expression is dependent on the collagen-binding integrin alpha1beta1 on VSMCs. These data suggest that SPRR3 may play a role in VSMC adaptation to local biomechanical stress within the plaque microenvironment.

VEGF and PlGF promote adult vasculogenesis by enhancing EPC recruitment and vessel formation at the site of tumor neovascularization.

There are growing data to suggest that tissue hypoxia represents a critical force that drives adult vasculogenesis. Vascular endothelial growth factor (VEGF) expression is dramatically up-regulated by hypoxia and results in enhanced neovascularization. Although the role of VEGF in angiogenesis has been well characterized, its role in adult vasculogenesis remains poorly understood. We used two distinct murine bone marrow transplantation (BMT) models to demonstrate that increased VEGF levels at the site of tumor growth promoted vasculogenesis in vivo. This effect of VEGF was downstream of its effect to enhance either mobilization or survival of circulating endothelial progenitor cells (EPCs). Both VEGFR1 (flt1) and VEGFR2 (flk1) are expressed on culture expanded human EPCs. Previous studies suggest that the effect of VEGF on endothelial cell migration is primarily mediated via VEGFR2; however, VEGF-induced EPC migration in vitro was mediated by both receptors, suggesting that VEGF-VEGFR1 interactions in EPCs are distinct from differentiated endothelial cells. We used specific blocking antibodies to these receptors to demonstrate that VEGFR1 plays an important role in human EPC recruitment to tumors. These findings were further supported by our finding that tumor-associated placental growth factor (PlGF), a VEGFR1-specific agonist, increased tumor vasculogenesis in a murine BMT model. We further showed that both VEGF receptors were necessary for the formation of functional vessels derived from exogenously administered human ex vivo expanded EPCs. Our data suggest local VEGF and/or PlGF expression promote vasculogenesis; VEGF plays a role in EPC recruitment and subsequent formation of functional vessels.

Performance characteristics of the Beckman Coulter total ßhCG (5th IS) assay.

BACKGROUND: Beckman Coulter recently released the first commercially available hCG reagent calibrated against the 5th International Standard (IS) for hCG (total ßhCG (5th IS)). We performed a comprehensive analytical validation of this reagent. METHODS: Precision experiments were completed using 3 concentrations of commercial quality control material. Linearity, sample stability, and analytical sensitivity were evaluated using pools of human serum. Reportable range was assessed by comparing manual dilutions to those performed by the instrument. Male and female reference intervals were established using residual serum specimens submitted for routine testing. Inter-lot variability of hCG assay reagent was assessed by analyzing serum specimens with detectable hCG using 2 different reagent lots. Inter-assay variability was established using 203 serum specimens analyzed for hCG on 6 different reagent platforms. RESULTS: Inter-day precision showed a CV of <6.0% for all concentrations of QC material. LOB, LOD, and LOQ were determined to be 0.3, 0.4, and 0.6 U/l, respectively. The Access (5th IS) reagent has an average positive bias of approximately 20% when compared to most platforms and the previous generation Beckman hCG assay. Results were consistent between lots. Female reference intervals varied by age: <1.0 U/l (<41 y), <6.0 U/l (41-50 y), and <8.0 U/l (>50 y). Male reference intervals were <2.0 U/l. CONCLUSIONS: The analytical performance of the total ßhCG (5th IS) was established. Care should be taken to re-baseline patients needing serial monitoring and/or notify physicians when transitioning to the total ßhCG (5th IS) reagent.

Crucial roles of the protein kinases MK2 and MK3 in a mouse model of glomerulonephritis.

Elevated mitogen-activated protein kinase p38 (p38 MAPK) signaling has been implicated in various experimental and human glomerulopathies, and its inhibition has proven beneficial in animal models of these diseases. p38 MAPK signaling is partially mediated through MK2 and MK3, two phylogenetically related protein kinases that are its direct substrates. The current study was designed to determine the specific roles of MK2 and MK3 in a mouse model of acute proliferative glomerulonephritis, using mice with disrupted MK2 and/or MK3 genes. We found that the absence of MK3 alone worsened the disease course and increased mortality slightly compared to wild-type mice, whereas the absence of MK2 alone exhibited no significant effect. However, in an MK3-free background, the disease course depended on the presence of MK2 in a gene dosage-dependent manner, with double knock-out mice being most susceptible to disease induction. Histological and renal functional analyses confirmed kidney damage following disease induction. Because the renal stress response plays a crucial role in kidney physiology and disease, we analyzed the stress response pattern in this disease model. We found that renal cortices of diseased mice exhibited a pronounced and specific pattern of expression and/or phosphorylation of stress proteins and other indicators of the stress response (HSPB1, HSPB6, HSPB8, CHOP, eIF2α), partially in a MK2/MK3 genotype-specific manner, and without induction of a general stress response. Similarly, the expression and activation patterns of other protein kinases downstream of p38 MAPK (MNK1, MSK1) depended partially on the MK2/MK3 genotype in this disease model. In conclusion, MK2 and MK3 together play crucial roles in the regulation of the renal stress response and in the development of glomerulonephritis, which can potentially be exploited to develop novel therapeutic approaches to treat glomerular disease.

Comparison of Sebia Capillarys Flex capillary electrophoresis with the BioRad Variant II high pressure liquid chromatography in the evaluation of hemoglobinopathies.

BACKGROUND: There are multiple biochemical screening techniques for assessing hemoglobinopathies. Here we compare a new instrument, the Sebia Capillarys Flex (capillary zone electrophoresis (CE)), with the BioRad Variant II (high pressure liquid chromatography (HPLC) in the evaluation of hemoglobinopathies. METHODS: This was a retrospective study using 174 whole blood samples encompassing the 5 most common (Hb A, A2', S, C, and E) and 10 rare (Hb G(Philidelphia), D, H, Bart's, O(Arab), S/G(Philidelphia), Hasharoon, Q(India), N(Baltimore), and Malmo) hemoglobin variants. An additional 126 samples were used to establish a CE reference interval for Hb A2. RESULTS: Hb A measurements agreed well between the 2 methods (bias=-0.06;r=0.999). The agreement of Hb F was also very good (bias=-0.17; r=0.994). When samples with the highest Hb F concentration were excluded, agreement was less precise (bias=-0.44; r=0.811). When no variant was present, the Hb A2 concentrations showed excellent agreement (bias=0.00; r=0.994). Positive bias for Hb A2 is seen when Hb C is present using CE. The Hb A2 reference interval using CE was <3.2%. CONCLUSION: The Capillarys Flex is capable of identifying and quantifying hemoglobin species, consistent with existing HPLC methods.

Biomechanical stress induces novel arterial intima-enriched genes: implications for vascular adaptation to stress.

BACKGROUND: The arterial vasculature is subjected to considerably greater biomechanical stress than the venous circulation. This is reflected in the difference in morphology between large arteries and veins, however little is known about the molecular differences that arise as a consequence of biomechanical stress. Previously, we identified a group of arterial intima-enriched (AIE) genes: sciellin, periplakin, SPRR3, envoplakin, galectin 7, and plakoglobin that are functionally related in that they contribute to the stress properties of stratified epithelium. We sought to test our hypothesis that these genes were regulated by biomechanical stress in vascular smooth muscle cells (VSMCs). METHODS: Immunofluorescence was employed to determine the expression of the AIE genes in saphenous vein coronary artery bypass grafts. Furthermore, we used a model of cyclic stress to determine if the AIE genes were regulated by biomechanical stress in VSMCs in vitro. RESULTS: Sciellin and periplakin were upregulated in saphenous vein coronary artery bypass grafts after arterialization, but were absent in non-arterialized saphenous veins. Sciellin, SPRR3, and periplakin transcripts were all upregulated (4.67-, 4.95-, 2.77-fold, respectively) by prolonged exposure to cyclic strain (24-72 h), but not at earlier time points. CONCLUSIONS: These findings suggest a novel role for several human AIE genes in the VSMC response to arterialization and extended cyclic strain. SUMMARY: Biomechanical stress has long been implicated in vascular pathologies. We report the novel finding of a group of genes, previously studied in stratified epithelium, that were regulated by prolonged cyclic stress in vascular smooth muscle cells. This may have important implications to vascular disease.

TNP-470 inhibits 7,12-dimethylbenz[a]anthracene-induced mammary tumor formation when administered before the formation of carcinoma in situ but is not additive with tamoxifen.

In many women pathologic lesions, such as hyperplasia and carcinoma in situ, precede invasive breast cancer. We have shown that tissue vascularity increases with histologic progression to invasive disease. Similarly, in the well-characterized 7,12-dimethylbenz[a]anthracene (DMBA) model of mammary tumorigenesis, preinvasive lesions exhibit increased vascularity with progression. Using this model we asked whether inhibition of angiogenesis would block progression and if so, at which stage. We treated rats with DMBA followed by the potent angiogenic inhibitor, TNP-470, and/or tamoxifen starting 1 day or 6 weeks later. Histopathology and in vitro angiogenic potential of mammary organoids were evaluated 3 months after DMBA. All statistical tests were two-sided. Early TNP-470 and tamoxifen treatment inhibited the formation of carcinoma in situ (p < 0.001) and invasive disease (p < 0.001). However, their effects were not additive, despite their unique mechanisms of action. TNP-470 administration begun at the time of microscopic carcinoma in situ formation was unable to prevent the further development of carcinoma in situ or invasive breast cancer, whereas tamoxifen was highly effective (p = 0.001). There was no added benefit of combining TNP-470 and tamoxifen. TNP-470 therapy, unlike tamoxifen, did not inhibit the angiogenic potential of DMBA-treated normal mammary organoids, supporting its lack of a direct effect on the epithelium. These data provide proof-in-principle that inhibition of angiogenesis early in mammary tumorigenesis prevents mammary tumor formation in a hormone-sensitive model, indicating that angiogenesis is a potential target for cancer chemoprevention. Interactions with other chemopreventive strategies and the timing of administration must be thoroughly examined in vivo.