Lipoproteins and lipids in cardiovascular disease: from mechanistic insights to therapeutic targeting

With cardiovascular disease being the leading cause of morbidity and mortality worldwide, effective and costefficient therapies to reduce cardiovascular risk are highly needed. Lipids and lipoprotein particles crucially contribute to atherosclerosis as underlying pathology of cardiovascular disease and influence inflammatory processes as well as function of leukocytes, vascular and cardiac cells, thereby impacting on vessels and heart. Statins form the first-line therapy with the aim to block cholesterol synthesis, but additional lipid-lowering drugs are sometimes needed to achieve low-density lipoprotein (LDL) cholesterol target values. Furthermore, beyond LDL cholesterol, also other lipid mediators contribute to cardiovascular risk. This review comprehensively discusses low- and high-density lipoprotein cholesterol, lipoprotein (a), triglycerides as well as fatty acids and derivatives in the context of cardiovascular disease, providing mechanistic insights into their role in pathological processes impacting on cardiovascular disease. Also, an overview of applied as well as emerging therapeutic strategies to reduce lipid-induced cardiovascular burden is provided. (C) 2020 The Author(s). Published by Elsevier B.V

Lipoproteins and lipids in cardiovascular disease:from mechanistic insights to therapeutic targeting

With cardiovascular disease being the leading cause of morbidity and mortality worldwide, effective and costefficient therapies to reduce cardiovascular risk are highly needed. Lipids and lipoprotein particles crucially contribute to atherosclerosis as underlying pathology of cardiovascular disease and influence inflammatory processes as well as function of leukocytes, vascular and cardiac cells, thereby impacting on vessels and heart. Statins form the first-line therapy with the aim to block cholesterol synthesis, but additional lipid-lowering drugs are sometimes needed to achieve low-density lipoprotein (LDL) cholesterol target values. Furthermore, beyond LDL cholesterol, also other lipid mediators contribute to cardiovascular risk. This review comprehensively discusses low- and high-density lipoprotein cholesterol, lipoprotein (a), triglycerides as well as fatty acids and derivatives in the context of cardiovascular disease, providing mechanistic insights into their role in pathological processes impacting on cardiovascular disease. Also, an overview of applied as well as emerging therapeutic strategies to reduce lipid-induced cardiovascular burden is provided. (C) 2020 The Author(s). Published by Elsevier B.V

The role of Macrophage Migration Inhibitory Factor in Critical Illness

Emerging evidence suggests a crucial role for Macrophage Migration Inhibitory Factor (MIF) within the adaptive and innate immune system. In contrast to most cytokines, MIF is stored in preformed cytoplasmatic vesicles of various cell types enabling a rapid release in response to various inflammatory stimuli such as infection, surgical stress, hypoxia, ischemia and reperfusion. MIF acts as key player within the inflammatory cascade and provides several biological functions such as control of cell growth and arrest (activation of ERK1/2), sensing of pathogen stimuli (up regulation of TLR4 expression), inhibition of glucocorticoid induced immunosuppression and prevention of p53-mediated apoptosis of macrophages. The functional role of MIF within inflammation and infection seems however ambiguous: On the one hand, the pro-inflammatory effects of MIF are essential for an effective host defense. On the other hand, an overwhelming MIF release might be associated with organ dysfunction and various deleterious effects. Even more puzzling, recent data indicate a protective role of this pleiotrope cytokine during ischemia and reperfusion. This review focuses on new insights regarding the biological significance of MIF release in the context of critical illness and ischemia/reperfusion.status: publishe

Soluble CD74 Reroutes MIF/CXCR4/AKT-Mediated Survival of Cardiac Myofibroblasts to Necroptosis

Background: Although macrophage migration inhibitory factor (MIF) has been demonstrated to mediate cardioprotection in ischemia/reperfusion injury and antagonize fibrotic effects through its receptor, CD74, the function of the soluble CD74 receptor ectodomain (sCD74) and its interaction with circulating MIF have not been explored in cardiac disease. Methods and Results: Cardiac fibroblasts were isolated from hearts of neonatal mice and differentiated into myofibroblasts. Co-treatment with recombinant MIF and sCD74 induced cell death (P<0.001), which was mediated by receptor-interacting serine/threonine-protein kinase (RIP) 1/RIP3-dependent necroptosis (P=0.0376). This effect was specific for cardiac fibroblasts and did not affect cardiomyocytes. Gene expression analyses using microarray and RT-qPCR technology revealed a 4-fold upregulation of several interferon-induced genes upon co-treatment of myofibroblasts with sCD74 and MIF (Ifi44: P=0.011;Irg1: P=0.022;Clec4e: P=0.011). Furthermore, Western blot analysis confirmed the role of sCD74 as a modulator of MIF signaling by diminishing MIF-mediated protein kinase B (AKT) activation (P=0.0197) and triggering p38 activation (P=0.0641). We obtained evidence that sCD74 inhibits MIF-mediated survival pathway through the C-X-C chemokine receptor 4/AKT axis, enabling the induction of CD74-dependent necroptotic processes in cardiac myofibroblasts. Preliminary clinical data revealed a lowered sCD74/MIF ratio in heart failure patients (17.47 +/- 10.09 versus 1.413 +/- 0.6244). Conclusions: These findings suggest that treatment of cardiac myofibroblasts with sCD74 and MIF induces necroptosis, offering new insights into the mechanism of myofibroblast depletion during scar maturation. Preliminary clinical data provided first evidence about a clinical relevance of the sCD74/MIF axis in heart failure, suggesting that these proteins may be a promising target to modulate cardiac remodeling and disease progression in heart failure

Argon Induces Protective Effects in Cardiomyocytes during the Second Window of Preconditioning

Increasing evidence indicates that argon has organoprotective properties. So far, the underlying mechanisms remain poorly understood. Therefore, we investigated the effect of argon preconditioning in cardiomyocytes within the first and second window of preconditioning. Primary isolated cardiomyocytes from neonatal rats were subjected to 50% argon for 1 h, and subsequently exposed to a sublethal dosage of hypoxia (&lt;1% O2) for 5 h either within the first (0–3 h) or second window (24–48 h) of preconditioning. Subsequently, the cell viability and proliferation was measured. The argon-induced effects were assessed by evaluation of mRNA and protein expression after preconditioning. Argon preconditioning did not show any cardioprotective effects in the early window of preconditioning, whereas it leads to a significant increase of cell viability 24 h after preconditioning compared to untreated cells (p = 0.015) independent of proliferation. Argon-preconditioning significantly increased the mRNA expression of heat shock protein (HSP) B1 (HSP27) (p = 0.048), superoxide dismutase 2 (SOD2) (p = 0.001), vascular endothelial growth factor (VEGF) (p &lt; 0.001) and inducible nitric oxide synthase (iNOS) (p = 0.001). No difference was found with respect to activation of pro-survival kinases in the early and late window of preconditioning. The findings provide the first evidence of argon-induced effects on the survival of cardiomyocytes during the second window of preconditioning, which may be mediated through the induction of HSP27, SOD2, VEGF and iNOS

The Role of Macrophage Migration Inhibitory Factor in Adipose-Derived Stem Cells Under Hypoxia

Background: Adipose-derived stem cells (ASCs) are multipotent mesenchymal stem cells characterized by their strong regenerative potential and low oxygen consumption. Macrophage migration inhibitory factor (MIF) is a multifunctional chemokine-like cytokine that is involved in tissue hypoxia. MIF is not only a major immunomodulator but also is highly expressed in adipose tissue such as subcutaneous adipose tissue of chronic non-healing wounds. In the present study, we investigated the effect of hypoxia on MIF in ASCs isolated from healthy versus inflamed adipose tissue. Methods: Human ASCs were harvested from 17 patients (11 healthy adipose tissue samples, six specimens from chronic non-healing wounds). ASCs were treated in a hypoxia chamber at <1% oxygen. ASC viability, MIF secretion as well as expression levels of MIF, its receptor CD74, hypoxia-inducible transcription factor-1α (HIF-1α) and activation of the AKT and ERK signaling pathways were analyzed. The effect of recombinant MIF on the viability of ASCs was determined. Finally, the effect of MIF on the viability and production capacity of ASCs to produce the inflammatory cytokines tumor necrosis factor (TNF), interleukin (IL)-6, and IL-1β was determined upon treatment with recombinant MIF and/or a blocking MIF antibody. Results: Hypoxic treatment inhibited proliferation of ASCs derived from healthy or chronic non-healing wounds. ASCs from healthy adipose tissue samples were characterized by a low degree of MIF secretion during hypoxic challenge. In contrast, in ASCs from adipose tissue samples of chronic non-healing wounds, secretion and expression of MIF and CD74 expression were significantly elevated under hypoxia. This was accompanied by enhanced ERK signaling, while AKT signaling was not altered. Recombinant MIF did stimulate HIF-1α expression under hypoxia as well as AKT and ERK phosphorylation, while no effect on ASC viability was observed. Recombinant MIF significantly reduced the secretion of IL-1β under hypoxia and normoxia, and neutralizing MIF-antibodies diminished TNF-α and IL-1β release in hypoxic ASCs. Conclusions: Collectively, MIF did not affect the viability of ASCs from neither healthy donor site nor chronic wounds. Our results, however, suggest that MIF has an impact on the wound environment by modulating inflammatory factors such as IL-1β

Macrophage migration inhibitory factor (MIF) plasma concentration in critically ill COVID-19 patients: a prospective observational study

Mortality in critically ill coronavirus disease 2019 (COVID-19) patients is high and pharmacological treatment strategies remain limited. Early-stage predictive biomarkers are needed to identify patients with a high risk of severe clinical courses and to stratify treatment strategies. Macrophage migration inhibitory factor (MIF) was previously described as a potential predictor for the outcome of critically ill patients and for acute respiratory distress syndrome (ARDS), a hallmark of severe COVID-19 disease. This prospective observational study evaluates the predictive potential of MIF for the clinical outcome after severe COVID-19 infection. Plasma MIF concentrations were measured in 36 mechanically ventilated COVID-19 patients over three days after intensive care unit (ICU) admission. Increased compared to decreased MIF was significantly associated with aggravated organ function and a significantly lower 28-day survival (sequential organ failure assessment (SOFA) score; 8.2 ± 4.5 to 14.3 ± 3, p = 0.009 vs. 8.9 ± 1.9 to 12 ± 2, p = 0.296; survival: 56% vs. 93%; p = 0.003). Arterial hypertension was the predominant comorbidity in 85% of patients with increasing MIF concentrations (vs. decreasing MIF: 39%; p = 0.015). Without reaching significance, more patients with decreasing MIF were able to improve their ARDS status (p = 0.142). The identified association between an early MIF response, aggravation of organ function and 28-day survival may open future perspectives for biomarker-based diagnostic approaches for ICU management of COVID-19 patients

Operator design and mechanism for CarA repressor-mediated downregulation of the photo-inducible carB operon in Myxococcus xanthus. J.

The carB operon encodes all except one of the enzymes involved in light-induced carotenogenesis in Myxococcus xanthus. Expression of its promoter (PB) is repressed in the dark by sequence-specific DNA binding of CarA to a palindrome (pI) located between positions 47 and 64 relative to the transcription start site. This promotes subsequent binding of CarA to additional sites that remain to be defined. CarS, produced in the light, interacts physically with CarA, abrogates CarA-DNA binding, and thereby derepresses PB. In this study, we delineate the operator design that exists for CarA by precisely mapping out the second operator element. For this, we examined how stepwise deletions and site-directed mutagenesis in the region between the palindrome and the transcription start site affect CarA binding around PB in vitro and expression of PB in vivo. These revealed the second operator element to be an imperfect interrupted palindrome (pII) spanning positions 26 to 40. In vitro assays using purified M. xanthus RNA polymerase showed that CarA abolishes PB-RNA polymerase binding and runoff transcription and that both were restored by CarS, thus rationalizing the observations in vivo. CarA binding to pII (after association with pI) effectively occludes RNA polymerase from PB and so provides the operative mechanism for the repression of the carB o p e r o n b y C a r A . T h e b i p a r t i t e o p e r a t o r d e s i g n , whereby transcription is blocked by the low affinity CarA-pII binding and is readily restored by CarS, may have evolved to match the needs for a rapid and an effective response to lightThis work was supported in part by Grants BMC2000-1006 (to F. J. M.), BMC2002-03818 (to M. S.), and BMC2002-00539 and Programa Ramón y Cajal (to S. P.) from the Ministerio de Ciencia y Tecnología, Spain. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Supported by a fellowship from Fundación Séneca (Murcia-Spain).Peer reviewe