Silvia Pozzi

Estrogen Action in Neuroprotection and Brain Inflammation

Abstract:  The fertile period of womens life compared to menopause is associated with a lower incidence of degenerative inflammatory diseases. In brain, estrogens ameliorate brain performance and have positive effects on selected neural pathologies characterized by a strong inflammatory component. We thus hypothesized that the inflammatory response is a target of estrogen action; several studies including ours provided strong evidence to support this prediction. Microglia, the brains inflammatory cells, and circulating monocytes express the estrogen receptors ER‐α and ER‐β and their responsiveness in vivo and in vitro to pro‐inflammatory agents, such as lipopolysaccharide (LPS), is controlled by 17β‐estradiol (E2). Susceptibility of central nervous system (CNS) macrophage cells to E2 is also preserved in animal models of neuroinflammatory diseases, in which ER‐α seems to be specifically involved. At the molecular level, induction of inflammatory gene expression is blocked by E2. We recently observed that, differently from conventional anti‐inflammatory drugs, E2 stimulates a nongenomic event that interferes with the LPS signal transduction from the plasma membrane to cytoskeleton and intracellular effectors, which results in the inhibition of the nuclear translocation of NF‐κB, a transcription factor of inflammatory genes. Interference with NF‐κB intracellular trafficking is selectively mediated by ER‐α. In summary, evidence from basic research strongly indicates that the use of estrogenic drugs that can mimic the anti‐inflammatory activity of E2 might trigger beneficial effects against neurodegeneration in addition to carrying out their specific therapeutic function.

miR-205 regulates basement membrane deposition in human prostate: implications for cancer development.

The basement membrane (BM) is a layer of specialized extracellular matrix that surrounds normal prostate glands and preserves tissue integrity. Lack or discontinuity of the BM is a prerequisite for tumor cell invasion into interstitial spaces, thus favoring metastasis. Therefore, BM maintenance represents a barrier against cancer development and progression. In the study, we show that miR-205 participates in a network involving ΔNp63α, which is essential for maintenance of the BM in prostate epithelium. At the molecular level, ΔNp63α is able to enhance miR-205 transcription by binding to its promoter, whereas the microRNA can post-transcriptionally limit the amount of ΔNp63α protein, mostly by affecting ΔNp63α proteasomal degradation rather than through a canonical miRNA/target interaction. Functionally, miR-205 is able to control the deposition of laminin-332 and its receptor integrin-β4. Hence, pathological loss of miR-205, as widely observed in prostate cancer, may favor tumorigenesis by creating discontinuities in the BM. Here we demonstrate that therapeutic replacement of miR-205 in prostate cancer (PCa) cells can restore BM deposition and 3D organization into normal-like acinar structures, thus hampering cancer progression.

Transcriptional Network of p63 in Human Keratinocytes

p63 is a transcription factor required for the development and maintenance of ectodermal tissues in general, and skin keratinocytes in particular. The identification of its target genes is fundamental for understanding the complex network of gene regulation governing the development of epithelia. We report a list of almost 1000 targets derived from ChIP on chip analysis on two platforms; all genes analyzed changed in expression during differentiation of human keratinocytes. Functional annotation highlighted unexpected GO terms enrichments and confirmed that genes involved in transcriptional regulation are the most significant. A detailed analysis of these transcriptional regulators in condition of perturbed p63 levels confirmed the role of p63 in the regulatory network. Rather than a rigid master-slave hierarchical model, our data indicate that p63 connects different hubs involved in the multiple specific functions of the skin.

eNOS Activation by HDL Is Impaired in Genetic CETP Deficiency.

Mutations in the CETP gene resulting in defective CETP activity have been shown to cause remarkable elevations of plasma HDL-C levels, with the accumulation in plasma of large, buoyant HDL particles enriched in apolipoprotein E. Genetic CETP deficiency thus represents a unique tool to evaluate how structural alterations of HDL impact on HDL atheroprotective functions. Aim of the present study was to assess the ability of HDL obtained from CETP-deficient subjects to protect endothelial cells from the development of endothelial dysfunction. HDL isolated from one homozygous and seven heterozygous carriers of CETP null mutations were evaluated for their ability to down-regulate cytokine-induced cell adhesion molecule expression and to promote NO production in cultured endothelial cells. When compared at the same protein concentration, HDL and HDL3 from carriers proved to be as effective as control HDL and HDL3 in down-regulating cytokine-induced VCAM-1, while carrier HDL2 were more effective than control HDL2 in inhibiting VCAM-1 expression. On the other hand, HDL and HDL fractions from carriers of CETP deficiency were significantly less effective than control HDL and HDL fractions in stimulating NO production, due to a reduced eNOS activating capacity, likely because of a reduced S1P content. In conclusion, the present findings support the notion that genetic CETP deficiency, by affecting HDL particle structure, impacts on HDL vasculoprotective functions. Understanding of these effects might be important for predicting the outcomes of pharmacological CETP inhibition.

Mutant p53 subverts p63 control over KLF4 expression in keratinocytes

Genetic experiments established that p63 is crucial for the development and maintenance of pluri-stratified epithelia and KLF4 for the barrier function of the skin. KLF4 is one of the factors that reprogram differentiated cells to iPS. We investigated the relationship between p63 and KLF4 using RNA interference, overexpression, chromatin immunoprecipitation and transient transfections with reporter constructs. We find that p63 directly represses KLF4 in normal keratinocytes (KCs) by binding to upstream promoter sites. Unlike p63, KLF4 levels are high in the upper layers of human skin and increase upon differentiation of KCs in vitro. In HaCaT KCs, which harbor two mutant alleles of p53, inactivation of p63 and of mutant p53 leads to KLF4 repression. p63 and p53 mutants are bound to sites in the KLF4 core promoter. Importantly, expression of the H179Y and R282Q p53 mutants in primary KCs is sufficient to activate endogenous KLF4. Finally, immunohistochemical analysis of tissue arrays confirms increased coexpression of KLF4 and mutant p53 in squamous cell carcinomas. Our data indicate that suppression of KLF4 is part of the growth-promoting strategy of p63 in the lower layers of normal epidermis, and that tumor-predisposing p53 mutations hijack p63 to a different location on the promoter, turning it into an activator of this reprogramming factor.

Low-flow Ischemia and Hypoxia Stimulate Apoptosis in Perfused Hearts Independently of Reperfusion

Post-ischemic reperfusion leads to apoptosis-linked loss of myocytes in cultured cells and in vivo. We tested the hypothesis that apoptosis develops without reperfusion in Langendorff-perfused hearts exposed to either low-flow ischemia (LFI) or hypoxia (H). Rat hearts were perfused with aminoacid-enriched Krebs-Henseleit buffer and exposed for 6 h to LFI (flow=2 ml/min, PO2=500±50mmHg, mean±SD), H (10ml/min, 120±15mmHg), or control conditions (C, 10ml/min, 500±50mmHg). At selected times, DNA-fragmentation was measured by agarose-gel electrophoresis and in situ TUNEL assay. After 6 h, the ratio (TUNEL-positive)/(total nuclei) was 0.620±0.027, 0.615±0.005, 0.404±0.021 in LFI, H and C, respectively. The ratio was 0.813±0.021 in hearts exposed to 90 min global no-flow ischemia and reperfused (5 h). To assess the role of membrane-diffusible factors, separate experiments were performed recirculating the medium and exposing hearts to LFI or H as above. The degree of apoptosis was the same in both the recirculating and non-recirculating modes. Thus, apoptosis develops by similar extents and in a time-dependent fashion in crystalloid-perfused rat hearts during LFI or H at the same oxygen shortage (flow · PO2), even without the reperfusion.

Structure and function of the apoA-IV T347S and Q360H common variants

Human apolipoprotein A-IV (apoA-IV) is involved in chylomicron assembly and secretion, and in reverse cholesterol transport. Several apoA-IV isoforms exist, the most common in Caucasian populations being apoA-IV-1a (T347S) and apoA-IV-2 (Q360H). The objective of the present study was to investigate the impact of these common aminoacid substitutions on the ability of apoA-IV to bind lipids, to promote cell cholesterol efflux via ABCA1, and to maintain endothelial homeostasis. Recombinant forms of wild-type apoA-IV, apoA-IV Q360H, and apoA-IV T347S were produced in Escherichia coli. ApoA-IV Q360H and apoA-IV T347S showed a slightly higher alpha-helical content compared to wild-type apoA-IV, and associated with phospholipids faster than wild-type apoA-IV. The capacity to promote ABCA1-mediated cholesterol efflux was significantly greater for the apoA-IV T347S than the other apoA-IV isoforms. No differences were observed in the ability of apoA-IV isoforms to inhibit the production of VCAM-1 and IL-6 in TNFalpha-stimulated endothelial cells. In conclusion, the apoA-IV T347S common variant has increased lipid binding properties and cholesterol efflux capacity, while the apoA-IV Q360H variant has only slightly increased lipid binding properties. The two common aminoacid substitutions have no effect on the ability of apoA-IV to maintain endothelial homeostasis.

Off-target effects of thrombolytic drugs: apolipoprotein A-I proteolysis by alteplase and tenecteplase

The administration of thrombolytic drugs is of proven benefit in a variety of clinical conditions requiring acute revascularization, including acute myocardial infarction (AMI), ischemic stroke, pulmonary embolism, and venous thrombosis. Generated plasmin can degrade non-target proteins, including apolipoprotein A-I (apoA-I), the major protein constituent of high-density lipoproteins (HDL). Aim of the present study was to compare the extent of apoA-I proteolytic degradation in AMI patients treated with two thrombolytic drugs, alteplase and the genetically engineered t-PA variant tenecteplase. ApoA-I degradation was evaluated in sera from 38 AMI patients treated with alteplase or tenecteplase. In vitro, apoA-I degradation was tested by incubating control sera or purified HDL with alteplase or tenecteplase at different concentrations (5-100 μg/ml). Treatment with alteplase and tenecteplase results in apoA-I proteolysis; the extent of apoA-I degradation was more pronounced in alteplase-treated patients than in tenecteplase-treated patients. In vitro, the extent of apoA-I proteolysis was higher in alteplase-treated sera than in tenecteplase-treated sera, in the whole drug concentration range. No direct effect of the two thrombolytic agents on apoA-I degradation was observed. In addition to apoA-I, apoA-IV was also degraded by the two thrombolytic agents and again proteolytic degradation was higher with alteplase than tenecteplase. In conclusion, this study indicates that both alteplase and tenecteplase cause plasmin-mediated proteolysis of apoA-I, with alteplase resulting in a greater apoA-I degradation than tenecteplase, potentially causing a transient impairment of HDL atheroprotective functions.

A Mouse Model of Familial ALS Has Increased CNS Levels of Endogenous Ubiquinol9/10 and Does Not Benefit from Exogenous Administration of Ubiquinol10

Oxidative stress and mitochondrial impairment are the main pathogenic mechanisms of Amyotrophic Lateral Sclerosis (ALS), a severe neurodegenerative disease still lacking of effective therapy. Recently, the coenzyme-Q (CoQ) complex, a key component of mitochondrial function and redox-state modulator, has raised interest for ALS treatment. However, while the oxidized form ubiquinone10 was ineffective in ALS patients and modestly effective in mouse models of ALS, no evidence was reported on the effect of the reduced form ubiquinol10, which has better bioavailability and antioxidant properties. In this study we compared the effects of ubiquinone10 and a new stabilized formulation of ubiquinol10 on the disease course of SOD1G93A transgenic mice, an experimental model of fALS. Chronic treatments (800 mg/kg/day orally) started from the onset of disease until death, to mimic the clinical trials that only include patients with definite ALS symptoms. Although the plasma levels of CoQ10 were significantly increased by both treatments (from <0.20 to 3.0–3.4 µg/mL), no effect was found on the disease progression and survival of SOD1G93A mice. The levels of CoQ10 in the brain and spinal cord of ubiquinone10- or ubiquinol10-treated mice were only slightly higher (≤10%) than the endogenous levels in vehicle-treated mice, indicating poor CNS availability after oral dosing and possibly explaining the lack of pharmacological effects. To further examine this issue, we measured the oxidized and reduced forms of CoQ9/10 in the plasma, brain and spinal cord of symptomatic SOD1G93A mice, in comparison with age-matched SOD1WT. Levels of ubiquinol9/10, but not ubiquinone9/10, were significantly higher in the CNS, but not in plasma, of SOD1G93A mice, suggesting that CoQ redox system might participate in the mechanisms trying to counteract the pathology progression. Therefore, the very low increases of CoQ10 induced by oral treatments in CNS might be not sufficient to provide significant neuroprotection in SOD1G93A mice.

Peroxisome Proliferator-Activated Receptor-α Is a Functional Target of p63 in Adult Human Keratinocytes

p63 is a master switch in the complex network of signaling pathways controlling the establishment and maintenance of stratified epithelia. We provide evidence that peroxisome proliferator-activated receptor-alpha (PPARalpha), a ligand-activated nuclear receptor that participates in the skin wound healing process, is a target of p63 in human keratinocytes. Silencing of p63 by RNA interference and transient transfections showed that p63 represses PPARalpha through a functional region of promoter B. Chromatin immunoprecipitation analyses indicate that p63 is bound to this region, in the absence of a recognizable p63-binding motif, suggesting that it acts through interactions with other transcription factors (TFs). Distinct PPARalpha transcripts are differentially regulated by p63, indicating a bimodal action in promoter and/or transcription start specification. PPARalpha repression is consistent with lack of expression in the interfollicular epidermis under physiological conditions. Furthermore, we show that PPARalpha is a negative regulator of DeltaNp63alpha levels and that it also binds to a functional region of the DeltaNp63 promoter that lacks PPRE motifs. Therefore, the reciprocal regulation is exerted either through binding to non-consensus sites or through interactions with other DNA-bound TFs. In conclusion, our data establish a link between two TFs intimately involved in the maintenance of skin homeostatic conditions.