Intensive receptor blockade and plasma exchange to treat refractory scleroderma renal crisis in patients with agonistic autoantibodies targeting the angiotensin II type 1 and endothelin-1 type A receptors.

Scleroderma renal crisis is a rare complication of systemic sclerosis characterized by a rapid decline in kidney function due to acute renal vascular injury. Recently, activating autoantibodies targeting the angiotensin II type 1 receptor and the endothelin-1 type A receptor have been implicated in the pathophysiology of scleroderma renal crisis by sensitizing the angiotensin II type 1 receptor and endothelin-1 type A receptor in renal resistance arteries to their natural ligands. Here, we describe a cohort of 10 patients with scleroderma renal crisis refractory to standard treatment, including blockade of the renin-angiotensin system. Multimodal therapy was initiated, targeting at the removal of anti-angiotensin II type 1 receptor and anti-endothelin-1 type A receptor autoantibodies by plasma exchange and the reduction of vasoconstrictive activity. Further treatment options included angiotensin II type 1 receptor and endothelin-1 type A receptor blockade, iloprost, intravenous immunoglobulins, and immunosuppression. Six patients were hypertensive. On kidney biopsy, concentric intimal sclerosis was present in all patients, whereas acute vascular injury was evident in eight. Levels of anti-angiotensin II type 1 receptor and anti-endothelin-1 type A receptor autoantibodies were significantly reduced by multimodal treatment. Kidney function improved in three patients with histological signs of severe acute renal vascular damage. This report demonstrates that intensive multimodal therapy taking account of potentially pathogenic anti-angiotensin II type 1 receptor and anti-endothelin-1 type A receptor autoantibodies in concert with other vasodilatory interventions provides a salvage option for patients with refractory scleroderma renal crisis.

Autoimmune activation and hypersensitization of the AT1 and ETA receptors contributes to vascular injury in scleroderma renal crisis.

OBJECTIVES: Scleroderma renal crisis (SRC) is a rare vascular complication of systemic sclerosis with substantial risks for end-stage renal disease and premature death. Activating autoantibodies (Abs) targeting the angiotensin II type 1 (AT1R) and the endothelin-1 type A receptor (ETAR) have been identified as predictors for SRC. Here, we sought to determine their pathogenic significance for acute renal vascular injury potentially triggering kidney failure and malignant hypertension. METHODS: IgG from patients with SRC was studied for AT1R and ETAR dependent biologic effects on isolated rat renal interlobar arteries and vascular cells including contraction, signalling and mechanisms of receptor activation. RESULTS: In myography experiments, patient IgG exerted vasoconstriction sensitive to inhibition of AT1R and ETAR. This relied on MEK-ERK signalling indicating functional relevance of anti-AT1R and anti-ETAR Abs. The contractile response to angiotensin II and endothelin-1 was amplified by patient IgG containing anti-AT1R and anti-ETAR Abs with substantial crosstalk between both receptors implicating autoimmune receptor hypersensitization. Co-immunoprecipitation experiments indicated heterodimerization between both receptor types which may enable the observed functional interrelation by direct structural interactions. CONCLUSION: We provide experimental evidence that agonistic Abs may contribute to SRC. This effect is presumably related to direct receptor stimulation and additional allosteric effects, at least in heterodimeric receptor constellations. Novel therapies targeted at autoimmune hyperactivation of AT1R and ETAR might improve outcomes in severe cases of SRC.

The mTOR inhibitor Rapamycin protects from premature cellular senescence early after experimental kidney transplantation.

Interstitial fibrosis and tubular atrophy, a major cause of kidney allograft dysfunction, has been linked to premature cellular senescence. The mTOR inhibitor Rapamycin protects from senescence in experimental models, but its antiproliferative properties have raised concern early after transplantation particularly at higher doses. Its effect on senescence has not been studied in kidney transplantation, yet. Rapamycin was applied to a rat kidney transplantation model (3 mg/kg bodyweight loading dose, 1.5 mg/kg bodyweight daily dose) for 7 days. Low Rapamycin trough levels (2.1-6.8 ng/mL) prevented the accumulation of p16INK4a positive cells in tubules, interstitium, and glomerula. Expression of the cytokines MCP-1, IL-1ß, and TNF-α, defining the proinflammatory senescence-associated secretory phenotype, was abrogated. Infiltration with monocytes/macrophages and CD8+ T-lymphocytes was reduced and tubular function was preserved by Rapamycin. Inhibition of mTOR was not associated with impaired structural recovery, higher glucose levels, or weight loss. mTOR inhibition with low-dose Rapamycin in the immediate posttransplant period protected from premature cellular senescence without negative effects on structural and functional recovery from preservation/reperfusion damage, glucose homeostasis, and growth in a rat kidney transplantation model. Reduced senescence might maintain the renal regenerative capacity rendering resilience to future injuries resulting in protection from interstitial fibrosis and tubular atrophy.

Low-dose rapamycin does not impair vascular integrity and tubular regeneration after kidney transplantation in rats.

mTOR inhibitors offer advantages after kidney transplantation including antiviral and antitumor activity besides facilitating low calcineurin inhibitor exposure to reduce nephrotoxicity. Concerns about adverse effects due to antiproliferative and antiangiogenic properties have limited their clinical use particularly early after transplantation. Interference with vascular endothelial growth factor (VEGF)-A, important for physiologic functioning of renal endothelial cells and tubular epithelium, has been implicated in detrimental renal effects of mTOR inhibitors. Low doses of Rapamycin (loading dose 3 mg/kg bodyweight, daily doses 1.5 mg/kg bodyweight) were administered in an allogenic rat kidney transplantation model resulting in a mean through concentration of 4.30 ng/mL. Glomerular and peritubular capillaries, tubular cell proliferation, or functional recovery from preservation/reperfusion injury were not compromised in comparison to vehicle treated animals. VEGF-A, VEGF receptor 2, and the co-receptor Neuropilin-1 were upregulated by Rapamycin within 7 days. Rat proximal tubular cells (RPTC) responded in vitro to hypoxia with increased VEGF-A and VEGF-R1 expression that was not suppressed by Rapamycin at therapeutic concentrations. Rapamycin did not impair proliferation of RPTC under hypoxic conditions. Low-dose Rapamycin early posttransplant does not negatively influence the VEGF network crucial for recovery from preservation/reperfusion injury. Enhancement of VEGF signaling peritransplant holds potential to further improve outcomes.

High cut-off dialysis mitigates pro-calcific effects of plasma on vascular progenitor cells.

Mortality of patients with end-stage renal disease tremendously exceeds that of the general population due to excess cardiovascular morbidity. Large middle-sized molecules (LMM) including pro-inflammatory cytokines are major drivers of uremic cardiovascular toxicity and cannot be removed sufficiently by conventional high-flux (HFL) hemodialysis. We tested the ability of plasma from 19 hemodialysis patients participating in a trial comparing HFL with high cut-off (HCO) membranes facilitating removal of LMM to induce calcification in mesenchymal stromal cells (MSC) functioning as vascular progenitors. HCO dialysis favorably changed plasma composition resulting in reduced pro-calcific activity. LMM were removed more effectively by HCO dialysis including FGF23, a typical LMM we found to promote osteoblastic differentiation of MSC. Protein-bound uremic retention solutes with known cardiovascular toxicity but not LMM inhibited proliferation of MSC without direct toxicity in screening experiments. We could not attribute the effect of HCO dialysis on MSC calcification to distinct mediators. However, we found evidence of sustained reduced inflammation that might parallel other anti-calcifying mechanisms such as altered generation of extracellular vesicles. Our findings imply protection of MSC from dysfunctional differentiation by novel dialysis techniques targeted at removal of LMM. HCO dialysis might preserve their physiologic role in vascular regeneration and improve outcomes in dialysis patients.

Autoantibodies Targeting AT1- and ETA-Receptors Link Endothelial Proliferation and Coagulation via Ets-1 Transcription Factor.

Scleroderma renal crisis (SRC) is an acute life-threatening manifestation of systemic sclerosis (SSc) caused by obliterative vasculopathy and thrombotic microangiopathy. Evidence suggests a pathogenic role of immunoglobulin G (IgG) targeting G-protein coupled receptors (GPCR). We therefore dissected SRC-associated vascular obliteration and investigated the specific effects of patient-derived IgG directed against angiotensin II type 1 (AT1R) and endothelin-1 type A receptors (ETAR) on downstream signaling events and endothelial cell proliferation. SRC-IgG triggered endothelial cell proliferation via activation of the mitogen-activated protein kinase (MAPK) pathway and subsequent activation of the E26 transformation-specific-1 transcription factor (Ets-1). Either AT1R or ETAR receptor inhibitors/shRNA abrogated endothelial proliferation, confirming receptor activation and Ets-1 signaling involvement. Binding of Ets-1 to the tissue factor (TF) promoter exclusively induced TF. In addition, TF inhibition prevented endothelial cell proliferation. Thus, our data revealed a thus far unknown link between SRC-IgG-induced intracellular signaling, endothelial cell proliferation and active coagulation in the context of obliterative vasculopathy and SRC. Patients' autoantibodies and their molecular effectors represent new therapeutic targets to address severe vascular complications in SSc.

Publisher Correction: mTORC1 and mTORC2 Differentially Regulate Cell Fate Programs to Coordinate Osteoblastic Differentiation in Mesenchymal Stromal Cells.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

mTORC1 and mTORC2 Differentially Regulate Cell Fate Programs to Coordinate Osteoblastic Differentiation in Mesenchymal Stromal Cells.

Vascular regeneration depends on intact function of progenitors of vascular smooth muscle cells such as pericytes and their circulating counterparts, mesenchymal stromal cells (MSC). Deregulated MSC differentiation and maladaptive cell fate programs associated with age and metabolic diseases may exacerbate arteriosclerosis due to excessive transformation to osteoblast-like calcifying cells. Targeting mTOR, a central controller of differentiation and cell fates, could offer novel therapeutic perspectives. In a cell culture model for osteoblastic differentiation of pluripotent human MSC we found distinct roles for mTORC1 and mTORC2 in the regulation of differentiation towards calcifying osteoblasts via cell fate programs in a temporally-controlled sequence. Activation of mTORC1 with induction of cellular senescence and apoptosis were hallmarks of transition to a calcifying phenotype. Inhibition of mTORC1 with Rapamycin elicited reciprocal activation of mTORC2, enhanced autophagy and recruited anti-apoptotic signals, conferring protection from calcification. Pharmacologic and genetic negative interference with mTORC2 function or autophagy both abolished regenerative programs but induced cellular senescence, apoptosis, and calcification. Overexpression of the mTORC2 constituent rictor revealed that enhanced mTORC2 signaling without altered mTORC1 function was sufficient to inhibit calcification. Studies in mice reproduced the in vitro effects of mTOR modulation with Rapamycin on cell fates in vascular cells in vivo. Amplification of mTORC2 signaling promotes protective cell fates including autophagy to counteract osteoblast differentiation and calcification of MSC, representing a novel mTORC2 function. Regenerative approaches aimed at modulating mTOR network activation patterns hold promise for delaying age-related vascular diseases and treatment of accelerated arteriosclerosis in chronic metabolic conditions.

Targeting proinflammatory cytokines ameliorates calcifying phenotype conversion of vascular progenitors under uremic conditions in vitro.

Severe vascular calcification develops almost invariably in chronic kidney patients posing a substantial risk to quality of life and survival. This unmet medical need demands identification of novel therapeutic modalities. We aimed to pinpoint components of the uremic microenvironment triggering differentiation of vascular progenitors to calcifying osteoblast-like cells. In an unbiased approach, assessing the individual potency of 63 uremic retention solutes to enhance calcific phenotype conversion of vascular progenitor cells, the pro-inflammatory cytokines IL-1ß and TNF-α were identified as the strongest inducers followed by FGF-2, and PTH. Pharmacologic targeting of these molecules alone or in combination additively antagonized pro-calcifying properties of sera from uremic patients. Our findings stress the importance of pro-inflammatory cytokines above other characteristic components of the uremic microenvironment as key mediators of calcifying osteoblastic differentiation in vascular progenitors. Belonging to the group of "middle-sized molecules", they are neither effectively removed by conventional dialysis nor influenced by established supportive therapies. Specific pharmacologic interventions or novel extracorporeal approaches may help preserve regenerative capacity and control vascular calcification due to uremic environment.

Intrinsic Deregulation of Vascular Smooth Muscle and Myofibroblast Differentiation in Mesenchymal Stromal Cells from Patients with Systemic Sclerosis.

INTRODUCTION: Obliterative vasculopathy and fibrosis are hallmarks of systemic sclerosis (SSc), a severe systemic autoimmune disease. Bone marrow-derived mesenchymal stromal cells (MSCs) from SSc patients may harbor disease-specific abnormalities. We hypothesized disturbed vascular smooth muscle cell (VSMC) differentiation with increased propensity towards myofibroblast differentiation in response to SSc-microenvironment defining growth factors and determined responsible mechanisms. METHODS: We studied responses of multipotent MSCs from SSc-patients (SSc-MSCs) and healthy controls (H-MSCs) to long-term exposure to CTGF, b-FGF, PDGF-BB or TGF-ß1. Differentiation towards VSMC and myofibroblast lineages was analyzed on phenotypic, biochemical, and functional levels. Intracellular signaling studies included analysis of TGF-ß receptor regulation, SMAD, AKT, ERK1/2 and autocrine loops. RESULTS: VSMC differentiation towards both, contractile and synthetic VSMC phenotypes in response to CTGF and b-FGF was disturbed in SSc-MSCs. H-MSCs and SSc-MSCs responded equally to PDGF-BB with prototypic fibroblastic differentiation. TGF-ß1 initiated myofibroblast differentiation in both cell types, yet with striking phenotypic and functional differences: In relation to H-MSC-derived myofibroblasts induced by TGF-ß1, those obtained from SSc-MSCs expressed more contractile proteins, migrated towards TGF-ß1, had low proliferative capacity, and secreted higher amounts of collagen paralleled by reduced MMP expression. Higher levels of TGF-ß receptor 1 and enhanced canonical and noncanonical TGF-ß signaling in SSc-MSCs accompanied aberrant differentiation response of SSc-MSCs in comparison to H-MSCs. CONCLUSIONS: Deregulated VSMC differentiation with a shift towards myofibroblast differentiation expands the concept of disturbed endogenous regenerative capacity of MSCs from SSc patients. Disease related intrinsic hyperresponsiveness to TGF-ß1 with increased collagen production may represent one responsible mechanism. Better understanding of repair barriers and harnessing beneficial differentiation processes in MSCs could widen options of autologous MSC application in SSc patients.

17ß-Estradiol regulates mTORC2 sensitivity to rapamycin in adaptive cardiac remodeling.

Adaptive cardiac remodeling is characterized by enhanced signaling of mTORC2 downstream kinase Akt. In females, 17ß-estradiol (E2), as well as Akt contribute essentially to sex-related premenopausal cardioprotection. Pharmacologic mTOR targeting with rapamycin is increasingly used for various clinical indications, yet burdened with clinical heterogeneity in therapy responses. The drug inhibits mTORC1 and less-so mTORC2. In male rodents, rapamycin decreases maladaptive cardiac hypertrophy whereas it leads to detrimental dilative cardiomyopathy in females. We hypothesized that mTOR inhibition could interfere with 17ß-estradiol (E2)-mediated sexual dimorphism and adaptive cell growth and tested responses in murine female hearts and cultured female cardiomyocytes. Under physiological in vivo conditions, rapamycin compromised mTORC2 function only in female, but not in male murine hearts. In cultured female cardiomyocytes, rapamycin impaired simultaneously IGF-1 induced activation of both mTOR signaling branches, mTORC1 and mTORC2 only in presence of E2. Use of specific estrogen receptor (ER)α- and ERß-agonists indicated involvement of both estrogen receptors (ER) in rapamycin effects on mTORC1 and mTORC2. Classical feedback mechanisms common in tumour cells with upregulation of PI3K signaling were not involved. E2 effect on Akt-pS473 downregulation by rapamycin was independent of ERK as shown by sequential mTOR and MEK-inhibition. Furthermore, regulatory mTORC2 complex defining component rictor phosphorylation at Ser1235, known to interfere with Akt-substrate binding to mTORC2, was not altered. Functionally, rapamycin significantly reduced trophic effect of E2 on cell size. In addition, cardiomyocytes with reduced Akt-pS473 under rapamycin treatment displayed decreased SERCA2A mRNA and protein expression suggesting negative functional consequences on cardiomyocyte contractility. Rictor silencing confirmed regulation of SERCA2A expression by mTORC2 in E2-cultured female cardiomyocytes. These data highlight a novel modulatory function of E2 on rapamycin effect on mTORC2 in female cardiomyocytes and regulation of SERCA2A expression by mTORC2. Conceivably, rapamycin abrogates the premenopausal "female advantage".

Sex-specific mTOR signaling determines sexual dimorphism in myocardial adaptation in normotensive DOCA-salt model.

The deoxycorticosterone acetate (DOCA)-salt mouse model exhibits adverse cardiac remodeling in male mice and cardiac protection in female mice, even when blood pressure is normalized. We hypothesized that intact mammalian target of rapamycin (mTOR) signaling is necessary for cardiac protection in females. We first tested sex differences and intracellular signaling after mTOR targeting with rapamycin in wild-type mice. Radio-telemetric blood pressure was maintained at normal for 6 weeks. Rapamycin significantly reduced left ventricular hypertrophy, preserved ejection fraction, inhibited fibrosis, and maintained capillary structure in male mice. Decreased mTORC1 and increased mTORC2 activity were detected in rapamycin-treated male mice compared with vehicle controls. In contrast, female mice developed dilative left ventricular hypertrophy, cardiac fibrosis, and capillary loss similar to DOCA-salt females lacking the estrogen receptor ß (ERß(-/-)) that we described earlier. Because rapamycin downregulated ERß in female mice, we next studied ERß(-/-) normotensive DOCA-salt females. Vehicle-treated wild-type females maintained their high constitutive mTORC1 and mTORC2 in response to DOCA-salt. In contrast to males, both mTORCs were decreased by rapamycin, in particular mTORC2 by 60%. ERß(-/-) DOCA-salt females showed similar mTORC1 and mTORC2 response patterns. We suggest that ERß-dependent regulation involves sex-specific use of mTOR signaling branches. Maintenance of both mTORC1 and mTORC2 signaling seems to be essential for adaptive cardiac remodeling in females and supports a rationale for sex-specific therapeutic strategies in left ventricular hypertrophy.

Estrogen receptor-beta signals left ventricular hypertrophy sex differences in normotensive deoxycorticosterone acetate-salt mice.

We found earlier that deoxycorticosterone acetate-salt treatment causes blood pressure-independent left ventricular hypertrophy, but only in male mice. To test the hypothesis that the estrogen receptor-ß (ERß) protects the females from left ventricular hypertrophy, we treated male and female ERß-deficient (ERß(-/-)) mice and their male and female littermates (wild-type [WT]) with deoxycorticosterone acetate-salt and made them telemetrically normotensive with hydralazine. WT males had increased (+16%) heart weight/tibia length ratios compared with WT females (+7%) at 6 weeks. In ERß(-/-) mice, this situation was reversed. Female WT mice had the greatest heart weight/tibia length ratio increases of all of the groups (+23%), even greater than ERß(-/-) males (+10%). Echocardiography revealed concentric left ventricular hypertrophy in male WT mice, whereas ERß(-/-) females developed dilative left ventricular hypertrophy. The hypertrophic response in female ERß(-/-) mice was accompanied by the highest degree of collagen deposition, indicating maladaptive remodeling. ERß(+/+) females showed robust protective p38 and extracellular signal-regulated kinase 1/2 signaling relationships compared with other groups. Calcineurin Aß expression and its positive regulator myocyte-enriched calcineurin-interacting protein 1 were increased in deoxycorticosterone acetate-salt female ERß(-/-) mice, yet lower than in WT males. Endothelin increased murine cardiomyocyte hypertrophy in vitro, which could be blocked by estradiol and an ERß agonist. We conclude that a functional ERß is essential for inducing adaptive p38 and extracellular signal-regulated kinase signaling, while reducing maladaptive calcineurin signaling in normotensive deoxycorticosterone acetate female mice. Our findings address the possibility of sex-specific cardiovascular therapies.

Involvement of functional autoantibodies against vascular receptors in systemic sclerosis.

BACKGROUND: Systemic sclerosis (SSc) features autoimmunity, vasculopathy and tissue fibrosis. The renin-angiotensin and endothelin systems have been implicated in vasculopathy and fibrosis. A role for autoantibody-mediated receptor stimulation is hypothesised, linking three major pathophysiological features consistent with SSc. METHODS: Serum samples from 478 patients with SSc (298 in the study cohort and 180 from two further independent cohorts), 372 healthy subjects and 311 control-disease subjects were tested for antibodies against angiotensin II type 1 receptor (AT(1)R) and endothelin-1 type A receptor (ET(A)R) by solid phase assay. Binding specificities were tested by immunoprecipitation. The biological effects of autoantibodies in microvascular endothelial cells in vitro were also determined, as well as the quantitative differences in autoantibody levels on specific organ involvements and their predictive value for SSc-related mortality. RESULTS: Anti-AT(1)R and anti-ET(A)R autoantibodies were detected in most patients with SSc. Autoantibodies specifically bound to respective receptors on endothelial cells. Higher levels of both autoantibodies were associated with more severe disease manifestations and predicted SSc-related mortality. Both autoantibodies exert biological effects as they induced extracellular signal-regulated kinase 1/2 phosphorylation and increased transforming growth factor ß gene expression in endothelial cells which could be blocked with specific receptor antagonists. CONCLUSIONS: Functional autoimmunity directed at AT(1)R and ET(A)R is common in patients with SSc. AT(1)R and ET(A)R autoantibodies could contribute to disease pathogenesis and may serve as biomarkers for risk assessment of disease progression.

Cytoprotective Actions of FTY720 Modulate Severe Preservation Reperfusion Injury in Rat Renal Transplants.

BACKGROUND: Fingolimod (FTY720) is a potent agonist of sphingosine 1 phosphate receptors and thereby interferes with lymphocyte trafficking. We previously showed that FTY720 protects from mild preservation reperfusion injury induced by 4 hr of cold ischemia. The purpose of this study was to explore the role of FTY720 in ischemic injury and regeneration using a clinically relevant rat renal transplant model with 24 hr of cold ischemia. METHODS: Donor kidneys were cold stored in the University of Wisconsin solution for 24 hr before transplantation into bilaterally nephrectomized syngeneic recipients (n=6 per group), which received 0.5 mg/kg/d FTY720 or vehicle through oral gavage. Grafts were harvested 2 or 7 days posttransplantation. Renal tissue was examined histologically, stained for apoptosis, proliferation, inflammatory cell infiltrates, and studied for transforming growth factor-beta, and tumor necrosis factor-alpha expression. Rat proximal tubular cells were incubated with 0.1 to 30 micromol/L of phosphorylated FTY720 to test for in vitro cytopathic effects. RESULTS: FTY720 induced peripheral lymphopenia and significantly reduced intragraft CD3 and ED1 infiltrates. Acute tubular damage scores and graft function were not influenced by FTY720. Tubular apoptosis was significantly reduced, whereas the number of proliferating cell nuclear antigen-positive tubular cells were markedly increased. FTY720 attenuated renal tumor necrosis factor-alpha and transforming growth factor-beta expression. In vitro, pharmacologic concentrations up to 1 micromol/L of phosphorylated FTY720 did not affect tubular cell viability. CONCLUSION: FTY720 confers tubular epithelial protection in the presence of severe preservation reperfusion injury. Beneficial effects may in part be due to reduction in cell-mediated immune mechanisms. Furthermore, FTY720 could be helpful in patients with delayed graft function.