Integrin-linked kinase mRNA expression in circulating mononuclear cells as a biomarker of kidney and vascular damage in experimental chronic kidney disease.

BACKGROUND: Traditional biomarkers of chronic kidney disease (CKD) detect the disease in its late stages and hardly predict associated vascular damage. Integrin-linked kinase (ILK) is a scaffolding protein and a serine/threonine protein kinase that plays multiple roles in several pathophysiological processes during renal damage. However, the involvement of ILK as a biomarker of CKD and its associated vascular problems remains to be fully elucidated. METHODS: CKD was induced by an adenine-rich diet for 6 weeks in mice. We used an inducible ILK knockdown mice (cKD-ILK) model to decrease ILK expression. ILK content in mice's peripheral blood mononuclear cells (PBMCs) was determined and correlated with renal function parameters and with the expression of ILK and fibrosis and inflammation markers in renal and aortic tissues. Also, the expression of five miRNAs that target ILK was analyzed in whole blood of mice. RESULTS: The adenine diet increased ILK expression in PBMCs, renal cortex, and aortas, and creatinine and urea nitrogen concentrations in the plasma of WT mice, while these increases were not observed in cKD-ILK mice. Furthermore, ILK content in PBMCs directly correlated with renal function parameters and with the expression of renal and vascular ILK and fibrosis and inflammation markers. Finally, the expression of the five miRNAs increased in the whole blood of adenine-fed mice, although only four correlated with plasma urea nitrogen, and of those, three were downregulated in cKD-ILK mice. CONCLUSIONS: ILK, in circulating mononuclear cells, could be a potential biomarker of CKD and CKD-associated renal and vascular damage.

Integrin Linked Kinase (ILK) Downregulation as an Early Event During the Development of Metabolic Alterations in a Short-Term High Fat Diet Mice Model.

BACKGROUND/AIMS: Diabetes type 2, metabolic syndrome or non-alcoholic fatty liver disease are insulin resistance-related metabolic disorders, which lack a better prognosis before their full establishment. We studied the importance of the intracellular scaffold protein integrin linked kinaes (ILK) as a key modulator in the initial pathogenesis and the early progression of those insulin resistance- related disorders. METHODS: Adult mice with a global transgenic downregulation of ILK expression (cKD-ILK) and littermates without that depletion (CT) were fed with either standard (STD) or high fat (HFD) diets during 2 and 6 weeks. Weights, blood glucose and other systemic biochemical parameters were determined in animals under fasting conditions and after glucose or pyruvate intraperitoneal injections to test their tolerance. In RNA or proteins extracted from insulin-sensitive tissues, we determined by reverse transcription-quantitative PCR and western blot the expression of ILK, metabolites transporters and other metabolism and inflammatory markers. Glucose uptake capacity was studied in freshly isolated tissues. RESULTS: HFD feeding was able to early and progressively increase glycaemia, insulinemia, circulating glycerol, body weight gain, liver-mediated gluconeogenesis along this time lapse, but cKD-ILK have all these systemic misbalances exacerbated compared to CT in the same HFD time lapse. Interestingly, the tisular expression of ILK in HFD-fed CT was dramatically downregulated in white adipose tissue (WAT), skeletal muscle and liver at the same extent of the original ILK downregulation of cKD-ILK. We previously published that basal STD-fed cKD-ILK compared to basal STD-CT have different expression of glucose transporters GLUT4 in WAT and skeletal muscle. In the same STD-fed cKD-ILK, we observed here the increased expressions of hepatic GLUT2 and WAT pro-inflammatory cytokines TNF-α and MCP-1. The administration of HFD exacerbated the expression changes in cKD-ILK of these and other markers related to the imbalanced metabolism observed, such as WAT lipolysis (HSL), hepatic gluconeogenesis (PCK-1) and glycerol transport (AQP9). CONCLUSION: ILK expression may be taken as a predictive determinant of metabolic disorders establishment, because its downregulation seems to correlate with the early imbalance of glucose and glycerol transport and the subsequent loss of systemic homeostasis of these metabolites.

H- ras deletion protects against angiotensin II-induced arterial hypertension and cardiac remodeling through protein kinase G-Iß pathway activation.

Ras proteins regulate cell survival, growth, differentiation, blood pressure, and fibrosis in some organs. We have demonstrated that H- ras gene deletion produces mice hypotension via a soluble guanylate cyclase-protein kinase G (PKG)-dependent mechanism. In this study, we analyzed the consequences of H- ras deletion on cardiac remodeling induced by continuous angiotensin II (AngII) infusion and the molecular mechanisms implied. Left ventricular posterior wall thickness and mass and cardiomyocyte cross-sectional area were similar between AngII-treated H-Ras knockout (H -ras-/-) and control wild-type (H -ras+/+) mice, as were extracellular matrix protein expression. Increased cardiac PKG-Iß protein expression in H -ras-/- mice suggests the involvement of this protein in heart protection. Ex vivo experiments on cardiac explants could support this mechanism, as PKG blockade blunted protection against AngII-induced cardiac hypertrophy and fibrosis markers in H -ras-/- mice. Genetic modulation studies in cardiomyocytes and cardiac and embryonic fibroblasts revealed that the lack of H-Ras down-regulates the B-RAF/MEK/ERK pathway, which induces the glycogen synthase kinase-3ß-dependent activation of the transcription factor, cAMP response element-binding protein, which is responsible for PKG-Iß overexpression in H -ras-/- mouse embryonic fibroblasts. This study demonstrates that H- ras deletion protects against AngII-induced cardiac remodeling, possibly via a mechanism in which PKG-Iß overexpression could play a partial role, and points to H-Ras and/or downstream proteins as potential therapeutic targets in cardiovascular disease.-Martín-Sánchez, P., Luengo, A., Griera, M., Orea, M. J., López-Olañeta, M., Chiloeches, A., Lara-Pezzi, E., de Frutos, S., Rodríguez-Puyol, M., Calleros, L., Rodríguez-Puyol, D. H- ras deletion protects against angiotensin II-induced arterial hypertension and cardiac remodeling through protein kinase G-Iß pathway activation.

ILK and cytoskeletal architecture: an important determinant of AQP2 recycling and subsequent entry into the exocytotic pathway.

Within the past decade tremendous efforts have been made to understand the mechanism behind aquaporin-2 (AQP2) water channel trafficking and recycling, to open a path toward effective diabetes insipidus therapeutics. A recent study has shown that integrin-linked kinase (ILK) conditional-knockdown mice developed polyuria along with decreased AQP2 expression. To understand whether ILK also regulates AQP2 trafficking in kidney tubular cells, we performed in vitro analysis using LLCPK1 cells stably expressing rat AQP2 (LLC-AQP2 cells). Upon treatment of LLC-AQP2 cells with ILK inhibitor cpd22 and ILK-siRNA, we observed increased accumulation of AQP2 in the perinuclear region, without any significant increase in the rate of endocytosis. This perinuclear accumulation did not occur in cells expressing a serine-256-aspartic acid mutation that retains AQP2 in the plasma membrane. We then examined clathrin-mediated endocytosis after ILK inhibition using rhodamine-conjugated transferrin. Despite no differences in overall transferrin endocytosis, the endocytosed transferrin also accumulated in the perinuclear region where it colocalized with AQP2. These accumulated vesicles also contained the recycling endosome marker Rab11. In parallel, the usual vasopressin-induced AQP2 membrane accumulation was prevented after ILK inhibition; however, ILK inhibition did not measurably affect AQP2 phosphorylation at serine-256 or its dephosphorylation at serine-261. Instead, we found that inhibition of ILK increased F-actin polymerization. When F-actin was depolymerized with latrunculin, the perinuclear located AQP2 dispersed. We conclude that ILK is important in orchestrating dynamic cytoskeletal architecture during recycling of AQP2, which is necessary for its subsequent entry into the exocytotic pathway.

Integrin-linked kinase regulates tubular aquaporin-2 content and intracellular location: a link between the extracellular matrix and water reabsorption.

One of the clinical alterations observed in chronic renal disease (CRD) is the impaired urine concentration, known as diabetes insipidus (DI). Tubulointerstitial fibrosis of the kidney is also a pathological finding observed in CRD and involves composition of extracellular matrix (ECM). However, an association between these two events has not been elucidated. In this study, we showed that the extracellular-to-intracellular scaffold protein integrin-linked kinase (ILK) regulates expression of tubular water channel aquaporin-2 (AQP2) and its apical membrane presence in the renal tubule. Basally, polyuria and decreased urine osmolality were present in ILK conditional-knockdown (cKD-ILK) adult mice compared with nondepleted ILK littermates. No changes were observed in arginine-vasopressin (AVP) blood levels, renal receptor (V2R), or AQP3 expression. However, tubular AQP2 was decreased in expression and apical membrane presence in cKD-ILK mice, where the canonical V2R/cAMP axis activation is still functional, but independent of the absence of ILK. Thus, cKD-ILK constitutes a nephrogenic diabetes insipidus (NDI) model. AQP2 and ILK colocalize in cultured inner medullary collecting duct (mIMCD3) cells. Specific ILK siRNAs and collagen I (Col) decrease ILK and AQP2 levels and AQP2 presence on the membrane of tubular mIMCD3 cells, which impairs the capacity of the cells to transport water under hypotonic stress. The present work points to ILK as a therapeutic target in NDI.

Blocking ephrinB2 with highly specific antibodies inhibits angiogenesis, lymphangiogenesis, and tumor growth.

Membrane-anchored ephrinB2 and its receptor EphB4 are involved in the formation of blood and lymphatic vessels in normal and pathologic conditions. Eph/ephrin activation requires cell-cell interactions and leads to bidirectional signaling pathways in both ligand- and receptor-expressing cells. To investigate the functional consequences of blocking ephrinB2 activity, 2 highly specific human single-chain Fv (scFv) Ab fragments against ephrinB2 were generated and characterized. Both Ab fragments suppressed endothelial cell migration and tube formation in vitro in response to VEGF and provoked abnormal cell motility and actin cytoskeleton alterations in isolated endothelial cells. As only one of them (B11) competed for binding of ephrinB2 to EphB4, these data suggest an EphB-receptor-independent blocking mechanism. Anti-ephrinB2 therapy reduced VEGF-induced neovascularization in a mouse Matrigel plug assay. Moreover, systemic administration of ephrinB2-blocking Abs caused a drastic reduction in the number of blood and lymphatic vessels in xenografted mice and a concomitant reduction in tumor growth. Our results show for the first time that specific Ab-based ephrinB2 targeting may represent an effective therapeutic strategy to be used as an alternative or in combination with existing antiangiogenic drugs for treating patients with cancer and other angiogenesis-related diseases.

A new graphene-based nanomaterial increases lipolysis and reduces body weight gain through integrin linked kinase (ILK).

White adipose tissue (WAT) hypertrophy is caused by the excessive storage of triglycerides (TGs) and is associated with obesity. We previously demonstrated that extracellular matrix mediator integrin beta1 (INTB1) and its downstream effector integrin linked kinase (ILK) are implicated in obesity establishment. We also considered in our previous works that ILK upregulation is a therapeutical strategy to reduce WAT hypertrophy. Carbon based nanomaterials (CNMs) have interesting potential to modify cell differentiation but have been never studied to change the properties of adipocytes. METHODS: GMC is a new graphene-based CNM that was tested for biocompatibility and functionality in cultured adipocytes. MTT, TG content, lipolysis quantification, and transcriptional changes were determined. Specific INTB1 blocking antibody and ILK depletion with specific siRNA were used to study the intracellular signalling. We complemented the study using subcutaneous WAT (scWAT) explants from transgenic ILK knockdown mice (cKD-ILK). GMC was topically administrated in the dorsal area of high fat diet-induced obese rats (HFD) for 5 consecutive days. The scWAT weights and some intracellular markers were analyzed after the treatment. RESULTS: graphene presence was characterized in GMC. It was non-toxic and effective in reducing TG content in vitro in a dose-dependent manner. GMC rapidly phosphorylated INTB1 and increased the expression and activity of hormone sensitive lipase (HSL), the lipolysis subproduct glycerol, and the expression of glycerol and fatty acid transporters. GMC also reduced the expression of adipogenesis markers. Pro-inflammatory cytokines were unaffected. ILK was overexpressed, and INTB1 or ILK blockade avoided functional GMC effects. Topical administration of GMC in HFD rats overexpressed ILK in scWAT, and their weight gains were reduced, while systemic (renal, hepatic) toxicity parameters were unaffected. CONCLUSIONS: GMC is safe and effective in reducing hypertrophied scWAT weight when topically applied and it can be considered of interest in anti-obesogenic strategies. GMC increases lipolysis and reduces adipogenesis inside adipocytes by mechanisms that imply the activation of INTB1, the overexpression of ILK, and changes in the expression and activity of several markers related to fat metabolism.

Indoxyl sulfate- and P-cresol-induced monocyte adhesion and migration is mediated by integrin-linked kinase-dependent podosome formation.

Cardiovascular disease is an important cause of death in patients with chronic kidney disease (CKD). Protein-bound uremic toxins, such as p-cresyl and indoxyl sulfate (IS), are poorly removed during hemodialysis, leading to vascular endothelial dysfunction and leukocyte extravasation. These processes can be related to dynamic adhesion structures called podosomes. Several studies have indicated the role of integrin-linked kinase (ILK) in the accumulation of integrin-associated proteins in podosomes. Here, we investigated the involvement of ILK and podosome formation in the adhesion and extravasation of monocytes under p-cresol (pc) and IS exposure. Incubation of THP-1 human monocyte cells with these toxins upregulated ILK kinase activity. Together, both toxins increased cell adhesion, podosome formation, extracellular matrix degradation, and migration of THP-1 cells, whereas ILK depletion with specific small interfering RNAs suppressed these processes. Interestingly, F-actin colocalized with cortactin in podosome cores, while ILK was colocalized in podosome rings under toxin stimulation. Podosome Wiskott-Aldrich syndrome protein (WASP)-interacting protein (WIP) and AKT protein depletion demonstrated that monocyte adhesion depends on podosome formation and that the ILK/AKT signaling pathway is involved in these processes. Ex vivo experiments showed that both toxins induced adhesion and podosome formation in leukocytes from wild-type mice, whereas these effects were not observed in leukocytes of conditional ILK-knockdown animals. In summary, under pc and IS stimulation, monocytes increase podosome formation and transmigratory capacity through an ILK/AKT signaling pathway-dependent mechanism, which could lead to vascular injury. Therefore, ILK could be a potential therapeutic target for the treatment of vascular damage associated with CKD.

Endothelin-1 contributes to increased NFATc3 activation by chronic hypoxia in pulmonary arteries.

Chronic hypoxia (CH) activates the Ca(2+)-dependent transcription factor nuclear factor of activated T cells isoform c3 (NFATc3) in mouse pulmonary arteries. However, the mechanism of this response has not been explored. Since we have demonstrated that NFATc3 is required for CH-induced pulmonary arterial remodeling, establishing how CH activates NFATc3 is physiologically significant. The goal of this study was to test the hypothesis that endothelin-1 (ET-1) contributes to CH-induced NFATc3 activation. We propose that this mechanism requires increased pulmonary arterial smooth muscle cell (PASMC) intracellular Ca(2+) concentration ([Ca(2+)](i)) and stimulation of RhoA/Rho kinase (ROK), leading to calcineurin activation and actin cytoskeleton polymerization, respectively. We found that: 1) CH increases pulmonary arterial pre-pro-ET-1 mRNA expression and lung RhoA activity; 2) inhibition of ET receptors, calcineurin, L-type Ca(2+) channels, and ROK blunts CH-induced NFATc3 activation in isolated intrapulmonary arteries from NFAT-luciferase reporter mice; and 3) both ET-1-induced NFATc3 activation in isolated mouse pulmonary arteries ex vivo and ET-1-induced NFATc3-green fluorescence protein nuclear import in human PASMC depend on ROK and actin polymerization. This study suggests that CH increases ET-1 expression, thereby elevating PASMC [Ca(2+)](i) and RhoA/ROK activity. As previously demonstrated, elevated [Ca(2+)](i) is required to activate calcineurin, which dephosphorylates NFATc3, allowing its nuclear import. Here, we demonstrate that ROK increases actin polymerization, thus providing structural support for NFATc3 nuclear transport.

Tripeptides as Integrin-Linked Kinase Modulating Agents Based on a Protein-Protein Interaction with α-Parvin.

Integrin-linked kinase (ILK) has emerged as a controversial pseudokinase protein that plays a crucial role in the signaling process initiated by integrin-mediated signaling. However, ILK also exhibits a scaffolding protein function inside cells, controlling cytoskeletal dynamics, and has been related to non-neoplastic diseases such as chronic kidney disease (CKD). Although this protein always acts as a heterotrimeric complex bound to PINCH and parvin adaptor proteins, the role of parvin proteins is currently not well understood. Using in silico approaches for the design, we have generated and prepared a set of new tripeptides mimicking an α-parvin segment. These derivatives exhibit activity in phenotypic assays in an ILK-dependent manner without altering kinase activity, thus allowing the generation of new chemical probes and drug candidates with interesting ILK-modulating activities.

NFATc3 contributes to intermittent hypoxia-induced arterial remodeling in mice.

Sleep apnea (SA) is defined as intermittent respiratory arrest during sleep and affects up to 20% of the adult population. SA is also associated with an increased incidence of hypertension and peripheral vascular disease. Exposing rodents to intermittent hypoxia during sleep mimics the cyclical hypoxia/normoxia of SA. We have previously shown that in mice and rats intermittent hypoxia induces ET-1 upregulation and systemic hypertension. Furthermore, intermittent hypoxia (IH) in mice increases nuclear factor of activated T cells isoform 3 (NFATc3) transcriptional activity in aorta and mesenteric arteries, whereas the calcineurin/NFAT inhibitor cyclosporin A prevents IH-induced hypertension. More importantly, NFATc3 knockout (KO) mice do not develop IH-induced hypertension. The goals of this study were to determine the role of NFATc3 in IH-induced arterial remodeling and whether IH-induced NFATc3 activation is mediated by ET-1. Oral administration of both a dual (bosentan) and a selective endothelin receptor type A antagonist (PD155080) during 2 days of IH exposure attenuated NFAT activation in aorta and mesenteric arteries. Rho kinase inhibition with fasudil also prevented IH-induced NFAT activation. Mesenteric artery cross-sectional wall thickness was increased by IH in wild-type (WT) and vehicle-treated mice but not in bosentan-treated and NFATc3 KO mice. The arterial remodeling in mesenteric arteries after IH was characterized by increased expression of the hypertrophic NFATc3 target smooth muscle-alpha-actin in WT but not in KO mice. These results indicate that ET-1 is an upstream activator of NFATc3 during intermittent hypoxia, contributing to the resultant hypertension and increased wall thickness.

Regulation of soluble guanylyl cyclase-alpha1 expression in chronic hypoxia-induced pulmonary hypertension: role of NFATc3 and HuR.

The nitric oxide/soluble guanylyl cyclase (sGC) signal transduction pathway plays an important role in smooth muscle relaxation and phenotypic regulation. However, the transcriptional regulation of sGC gene expression is largely unknown. It has been shown that sGC expression increases in pulmonary arteries from chronic hypoxia-induced pulmonary hypertensive animals. Since the transcription factor NFATc3 is required for the upregulation of the smooth muscle hypertrophic/differentiation marker alpha-actin in pulmonary artery smooth muscle cells from chronically hypoxic mice, we hypothesized that NFATc3 is required for the regulation of sGC-alpha1 expression during chronic hypoxia. Exposure to chronic hypoxia for 2 days induced a decrease in sGC-alpha1 expression in mouse pulmonary arteries. This reduction was independent of NFATc3 but mediated by nuclear accumulation of the mRNA-stabilizing protein human antigen R (HuR). Consistent with our hypothesis, chronic hypoxia (21 days) upregulated pulmonary artery sGC-alpha1 expression, bringing it back to the level of the normoxic controls. This response was prevented in NFATc3 knockout and cyclosporin (calcineurin/NFATc inhibitor)-treated mice. Furthermore, we identified effective binding sites for NFATc in the mouse sGC-alpha1 promoter. Activation of NFATc3 increased sGC-alpha1 promoter activity in human embryonic derived kidney cells, rat aortic-derived smooth muscle cells, and human pulmonary artery smooth muscle cells. Our results suggest that NFATc3 and HuR are important regulators of sGC-alpha1 expression in pulmonary vascular smooth muscle cells during chronic hypoxia-induced pulmonary hypertension.

Chronic kidney disease induced by an adenine rich diet upregulates integrin linked kinase (ILK) and its depletion prevents the disease progression.

Kidney fibrosis is one of the main pathological findings of progressive chronic kidney disease (CKD) although the pathogenesis of renal scar formation remains incompletely explained. Integrin-linked kinase (ILK), a major scaffold protein between the extracellular matrix (ECM) and intracellular signaling pathways, is involved in several pathophysiological processes during renal damage. However, ILK contribution in the CKD progress remains to be fully elucidated. In the present work, we studied 1) the renal functional and structural consequences of CKD genesis and progression when ILK is depleted and 2) the potential of ILK depletion as a therapeutic approach to delay CKD progression. We induced an experimental CKD model, based on an adenine-supplemented diet on adult wild-type (WT) and ILK-depleted mice, with a tubulointerstitial damage profile resembling that is observed in human CKD. The adenine diet induced in WT mice a progressive increase in plasma creatinine and urea concentrations. In the renal cortex it was also observed tubular damage, interstitial fibrosis and progressive increased ECM components, pro-inflammatory and chemo-attractant cytokines, EMT markers and TGF-ß1 expressions. These observations were highly correlated to a simultaneous increase of ILK expression and activity. In adenine-fed transgenic ILK-depleted mice, all these changes were prevented. Additionally, we evaluated the potential role of ILK depletion to be applied after the disease induction, as an effective approach to interventions in human CKD subjects. In this scenario, two weeks after the establishment of adenine-induced CKD, ILK was abrogated in WT mice and stabilized renal damage, avoiding CKD progression. We propose ILK to be a potential target to delay renal disease progression.

Contribution of uraemic toxins to the vascular fibrosis associated with chronic kidney disease. / Contribución de las toxinas urémicas a la fibrosis vascular asociada a la enfermedad renal crónica.

BACKGROUND: Patients with chronic kidney disease present with an accumulation of uraemic toxins, which have been identified as pathogenic agents associated with cardiovascular mortality, which is very high is this patient group. A phenomenon common to the progressive renal dysfunction and associated vascular damage, is the abnormal accumulation of extracellular matrix (ECM) proteins in the renal or vascular structures. OBJECTIVE: To determine the contribution of uraemia or the uraemic toxins to the production of cytokinins and ECM in aortas of uraemic animals or human aortic smooth muscle cells (HASMCs). MATERIALS AND METHODS: Mice were used with uraemia induced by a diet rich in adenine (0.2%) for 2, 4 or 6 weeks. Kidney function was evaluated by means of urine volume, plasma levels of creatinine, urea, fractional excretion of sodium, and vascular damage using histology, as well as protein expression using RT-qPCR. The HASMCs were incubated in vitro with uraemic toxins: p-cresol 10-100 (µg/ml) and indoxyl-sulphate25-100 (µg/ml) alone or simultaneously. The protein expression was evaluated using Western blot and confocal microscopy. RESULTS: The administration of adenine produced progressive kidney damage in the mice, thickening of the aortic wall, and increasing the expression of TGF-ß1 and ECM proteins. The toxins at high doses and combined also induced the expression of TGF-ß1 and ECM proteins by the HASMCs. CONCLUSIONS: The uraemia produced by an adenine rich diet or high doses of uraemic toxins induced the abnormal deposit of ECM proteins in the vascular wall or its production by HASMCs. The understanding of the mechanisms that underlie this pathophysiological process may be useful in the prevention of cardiovascular damage associated with the progress of chronic kidney disease, a disease, at the moment that is irreversible and occasional silent until its diagnosis in advanced stages.

Display of the Albumin-Binding Domain in the Envelope Improves Lentiviral Vector Bioavailability.

Vesicular stomatitis virus G glycoprotein (VSVg) is extensively used for retroviral and lentiviral vector (LV) pseudotyping. However, VSVg pseudotyped vectors are serum inactivated, blocking the in vivo gene delivery. Several strategies have been employed to prevent complement inactivation, including chemical and genetic envelope modifications. This study employed the streptococcal albumin-binding domain (ABD) to generate a construct to express ABD as a glycosylphosphatidylinositol-anchored protein. LV particles bearing ABD are able to bind bovine and human serum albumin in vitro. Neither the lentiviral vector production titer nor the in vitro transduction was affected by the ABD display. The study demonstrated that ABD-bearing LVs are protected from human complement inactivation. More importantly, intravenous administration demonstrated that the presence of ABD significantly reduces lentivector sequestration in liver and bone-marrow cells. Therefore, the use of ABD represents an improvement for in vivo gene therapy applications. The results strongly point to ABD display as a universal strategy to increase the in vivo efficacy of different viral vectors.

Peripheral insulin resistance in ILK-depleted mice by reduction of GLUT4 expression.

The development of insulin resistance is characterized by the impairment of glucose uptake mediated by glucose transporter 4 (GLUT4). Extracellular matrix changes are induced when the metabolic dysregulation is sustained. The present work was devoted to analyze the possible link between the extracellular-to-intracellular mediator integrin-linked kinase (ILK) and the peripheral tissue modification that leads to glucose homeostasis impairment. Mice with general depletion of ILK in adulthood (cKD-ILK) maintained in a chow diet exhibited increased glycemia and insulinemia concurrently with a reduction of the expression and membrane presence of GLUT4 in the insulin-sensitive peripheral tissues compared with their wild-type littermates (WT). Tolerance tests and insulin sensitivity indexes confirmed the insulin resistance in cKD-ILK, suggesting a similar stage to prediabetes in humans. Under randomly fed conditions, no differences between cKD-ILK and WT were observed in the expression of insulin receptor (IR-B) and its substrate IRS-1 expressions. The IR-B isoform phosphorylated at tyrosines 1150/1151 was increased, but the AKT phosphorylation in serine 473 was reduced in cKD-ILK tissues. Similarly, ILK-blocked myotubes reduced their GLUT4 promoter activity and GLUT4 expression levels. On the other hand, the glucose uptake capacity in response to exogenous insulin was impaired when ILK was blocked in vivo and in vitro, although IR/IRS/AKT phosphorylation states were increased but not different between groups. We conclude that ILK depletion modifies the transcription of GLUT4, which results in reduced peripheral insulin sensitivity and glucose uptake, suggesting ILK as a molecular target and a prognostic biomarker of insulin resistance.

Integrin linked kinase regulates the transcription of AQP2 by NFATC3.

Two processes are associated with progressive loss of renal function: 1) decreased aquaporin-2 (AQP2) expression and urinary concentrating capacity (Nephrogenic Diabetes Insipidus, NDI); and 2) changes in extracellular matrix (ECM) composition, e.g. increased collagen I (Col I) deposition, characteristic of tubule-interstitial fibrosis. AQP2 expression is regulated by both the ECM-to-intracellular scaffold protein integrin-linked kinase (ILK) by NFATc/AP1 and other transcription factors. In the present work, we used in vivo and in vitro approaches to examine ILK participation in NFATc3/AP-1-mediated increases in AQP2 gene expression. Both NFATc3 knock-out mice and ILK conditional-knockdown mice (cKD-ILK) display symptoms of NDI (polyuria and reduced AQP2 expression). NFATc3 is upregulated in the renal medulla tubular cells of cKD-ILK mice but with reduced nuclear localization. Inner medullary collecting duct mIMCD3 cells were subjected to ILK depletion and transfected with reporter plasmids. Pharmacological activators or inhibitors determined the effect of ILK activity on NFATc/AP-1-dependent increases in transcription of AQP2. Finally, mIMCD3 cultured on Col I showed reduced activity of the ILK/GSK3ß/NFATc/AQP2 axis, suggesting this pathway is a potential target for therapeutic treatment of NDI.

C-type natriuretic peptide decreases soluble guanylate cyclase levels by activating the proteasome pathway.

Natriuretic peptides (NP) activate particulate guanylate cyclase (pGC) and nitric oxide (NO) activates soluble guanylate cyclase (sGC). Both guanylate cyclases catalyse the formation of the same second messenger, cyclic guanosine 3',5'-monophosphate (cGMP), which activates the cGMP-dependent protein kinases (PKG). PKG then starts a signalling cascade that mediates many cardiovascular and renal effects, such as smooth muscle relaxation and diuresis. Many cell types possess both sGC and pGC. Because both GC-cGMP systems play complementary roles, an interaction between the two pathways might represent an important physiological control mechanism. In this report we demonstrate an interaction between the two pathways. C-type natriuretic peptide (CNP) decreased the beta-subunit of sGC (sGC-beta) steady-state protein levels and enzymatic activity in cultured human mesangial cells (HMC) in a time- and dose-dependent manner. This down-regulation was not dependent on changes in sGC-beta mRNA levels. Treatment of the cells with the stable cGMP analogue 8-Br-cGMP or the phosphodiesterase type-5 inhibitor Zaprinast produced the same down-regulatory effect. Inhibition of PKG or proteasome activity prevented the CNP-induced reduction of sGC-beta protein levels and activity. Taken together, these results demonstrate that pGC activation induces a post-transductional down-regulation of sGC by a mechanism involving PKG and the proteasome pathway.

Culture conditions influence uptake and intracellular localization of the membrane permeable cGMP-dependent protein kinase inhibitor DT-2.

The membrane-permeable peptide DT-2 which utilizes the HIV-Tat membrane translocation sequence is known to inhibit cGMP-dependent protein kinase (PKG) effectively in vitro and in various cell lines and tissue preparations. However, the uptake characteristics of DT-2 have not been studied in detail. We investigated the intracellular uptake and localization of fluorescein-labeled DT-2 (fDT-2) in cultured C6-glial cells and vascular smooth muscle cells (VSMCs) as well as VSMCs in intact arteries. To avoid fixation-induced fluorescence, live unfixed cells and arteries were incubated with fDT-2 and examined using conventional and confocal fluorescence microscopy. In non-differentiated cultured VSMCs, uptake appeared vesicular with nuclear exclusion, consistent with an endocytotic internalization mechanism. Inhibition of endocytosis by phenylarsine oxide (PAO), low temperature or disruption of actin polymerization by cytochalasin-D or lantrunculin-A showed a residual non-endocytotic fDT-2 translocation with diffuse cytosolic and nuclear uptake. Similarly, differentiated contractile VSMCs within the medial layer of intact cerebral arteries also showed a distinctively different, more diffuse cytosolic uptake and time dependent nuclear localization. To verify the morphology dependency of fDT-2 uptake, VSMCs were reconstituted in fibrillar collagen matrices. The cells adopted a differentiated morphology and fDT-2 translocation was similar to cells in intact arteries. These results demonstrate that VSMCs cells utilize distinct cellular uptake mechanisms depending on their phenotype.

Ilk conditional deletion in adult animals increases cyclic GMP-dependent vasorelaxation.

AIMS: Integrin-linked kinase (ILK) regulates proliferation, differentiation, cell adhesion, and motility in many cell types and has been related to cancer progression, fibrosis, and vascular diseases. We designed the present study to directly explore the effect of ILK deletion on the regulation of vascular tone through the soluble guanylate cyclase (sGC) /protein kinase G (PKG) pathway in healthy adult mice. METHODS AND RESULTS: Experiments were carried out using a tamoxifen-inducible CRE-LOX system to conditionally delete the ILK gene in adult mice. Mice lacking ILK expression (cKO) presented increased vascular content and increased activity of sGC and PKG, resulting in a more intense vasodilatory response to a single dose of a nitric oxide (NO) donor [sodium nitroprusside (SNP)] or PKG agonist [8-bromoguanosine 3',5'-cyclic monophosphate sodium salt (8-Br)]. Five minutes after SNP or 8-Br administration the reduction in the systolic arterial pressure was enhanced in cKO mice (SNP WT: -7.4 ± 1.2 mmHG; SNP cKO: -14.0 ± 2.5; 8-Br WT: -2.9 ± 1.5 mmHG; 8-Br cKO: -10.0 ± 3.4 mmHG). ILK deletion restored the vascular response to SNP after chronic oral nitrite administration. In addition, ILK deletion also increased hypotensive SNP effect in angiotensin II-treated animals, suggesting a role for ILK in basal and pathological states. CONCLUSION: Deletion of ILK in adult animals increased the vascular response to NO. These findings show, for the first time, a requirement for ILK in regulating sGC-PKG expression in vivo.