Senescent cells in giant cell arteritis display an inflammatory phenotype participating in tissue injury via IL-6-dependent pathways.

OBJECTIVES: Age is the strongest risk factor of giant cell arteritis (GCA), implying a possible pathogenetic role of cellular senescence. To address this question, we applied an established senescence specific multimarker algorithm in temporal artery biopsies (TABs) of GCA patients. METHODS: 75(+) TABs from GCA patients, 22(-) TABs from polymyalgia rheumatica (PMR) patients and 10(-) TABs from non-GCA/non-PMR patients were retrospectively retrieved and analysed. Synovial tissue specimens from patients with inflammatory arthritis and aorta tissue were used as disease control samples. Senescent cells and their histological origin were identified with specific cellular markers; IL-6 and MMP-9 were investigated as components of the senescent associated secretory phenotype by triple costaining. GCA or PMR artery culture supernatants were applied to fibroblasts, HUVECs and monocytes with or without IL-6R blocking agent to explore the induction of IL-6-associated cellular senescence. RESULTS: Senescent cells were present in GCA arteries at higher proportion compared with PMR (9.50% vs 2.66%, respectively, p<0.0001) and were mainly originated from fibroblasts, macrophages and endothelial cells. IL-6 was expressed by senescent fibroblasts, and macrophages while MMP-9 by senescent fibroblasts only. IL-6(+) senescent cells were associated with the extension of vascular inflammation (transmural inflammation vs adventitia limited disease: 10.02% vs 4.37%, respectively, p<0.0001). GCA but not PMR artery culture supernatant could induce IL-6-associated senescence that was partially inhibited by IL-6R blockade. CONCLUSIONS: Senescent cells with inflammatory phenotype are present in GCA arteries and are associated with the tissue inflammatory bulk, suggesting a potential implication in disease pathogenesis.

LPS-Induced Systemic Inflammation Affects the Dynamic Interactions of Astrocytes and Microglia with the Vasculature of the Mouse Brain Cortex.

The Neurovascular Unit (NVU), composed of glia (astrocytes, oligodendrocytes, microglia), neurons, pericytes and endothelial cells, is a dynamic interface ensuring the physiological functioning of the central nervous system (CNS), which gets affected and contributes to the pathology of several neurodegenerative diseases. Neuroinflammation is a common feature of neurodegenerative diseases and is primarily related to the activation state of perivascular microglia and astrocytes, which constitute two of its major cellular components. Our studies focus on monitoring in real time the morphological changes of perivascular astrocytes and microglia, as well as their dynamic interactions with the brain vasculature, under physiological conditions and following systemic neuroinflammation triggering both microgliosis and astrogliosis. To this end, we performed 2-photon laser scanning microscopy (2P-LSM) for intravital imaging of the cortex of transgenic mice visualizing the dynamics of microglia and astroglia following neuroinflammation induced by systemic administration of the endotoxin lipopolysaccharide (LPS). Our results indicate that following neuroinflammation the endfeet of activated perivascular astrocytes lose their close proximity and physiological cross-talk with vasculature, an event that most possibly contributes to a loss of blood-brain barrier (BBB) integrity. At the same time, microglial cells become activated and exhibit a higher extent of physical contact with the blood vessels. These dynamic responses of perivascular astrocytes and microglia are peaking at 4 days following LPS administration; however, they still persist at a lower level at 8 days after LPS injection, revealing incomplete reversal of inflammation affecting the glial properties and interactions within the NVU.

A miR-124-mediated post-transcriptional mechanism controlling the cell fate switch of astrocytes to induced neurons.

The microRNA (miRNA) miR-124 has been employed supplementary to neurogenic transcription factors (TFs) and other miRNAs to enhance direct neurogenic conversion. The aim of this study was to investigate whether miR-124 is sufficient to drive direct reprogramming of astrocytes to induced neurons (iNs) on its own and elucidate its independent mechanism of reprogramming action. Our data show that miR-124 is a potent driver of the reprogramming switch of astrocytes toward an immature neuronal fate by directly targeting the RNA-binding protein Zfp36L1 implicated in ARE-mediated mRNA decay and subsequently derepressing Zfp36L1 neurogenic interactome. To this end, miR-124 contribution in iNs' production largely recapitulates endogenous neurogenesis pathways, being further enhanced upon addition of the neurogenic compound ISX9, which greatly improves iNs' differentiation and functional maturation. Importantly, miR-124 is potent in guiding direct conversion of reactive astrocytes to immature iNs in vivo following cortical trauma, while ISX9 supplementation confers a survival advantage to newly produced iNs.

Down-regulation of KLF2 in lung fibroblasts is linked with COVID-19 immunofibrosis and restored by combined inhibition of NETs, JAK-1/2 and IL-6 signaling.

Kruppel-like factor 2 (KLF2) has been linked with fibrosis and neutrophil-associated thromboinflammation; however, its role in COVID-19 remains elusive. We investigated the effect of disease microenvironment on the fibrotic potential of human lung fibroblasts (LFs) and its association with KLF2 expression. LFs stimulated with plasma from severe COVID-19 patients down-regulated KLF2 expression at mRNA/protein and functional level acquiring a pre-fibrotic phenotype, as indicated by increased CCN2/collagen levels. Pre-incubation with the COMBI-treatment-agents (DNase I and JAKs/IL-6 inhibitors baricitinib/tocilizumab) restored KLF2 levels of LFs to normal abolishing their fibrotic activity. LFs stimulated with plasma from COMBI-treated patients at day-7 expressed lower CCN2 and higher KLF2 levels, compared to plasma prior-to-treatment, an effect not observed in standard-of-care treatment. In line with this, COMBI-treated patients had better outcome than standard-of-care group. These data link fibroblast KLF2 with NETosis and JAK/IL-6 signaling, suggesting the potential of combined therapeutic strategies in immunofibrotic diseases, such as COVID-19.

Neutrophil extracellular traps in giant cell arteritis biopsies: presentation, localization and co-expression with inflammatory cytokines.

OBJECTIVES: To explore the presence of neutrophil extracellular traps (NETs) in inflamed temporal artery biopsies (TABs) of patients with GCA. METHODS: Ten patients with GCA [five with limited and five with associated generalized vascular involvement, as defined by 18F-fluorodeoxyglucose PET with CT (PET/CT)] and eight with PMR were studied. The presence, location, quantitation and decoration of NETs with IL-6, IL-1ß and IL-17A were assessed in TABs at the time of disease diagnosis by tissue immunofluorescence and confocal microscopy. Paired serum levels of IL-6 and IL-17A were also evaluated in all patients. RESULTS: All temporal artery biopsies from GCA, but not PMR, patients had NETs located mainly in the adventitia, adjacent to the vasa vasorum. NETs decorated with IL-6 were present in 8/10 TABs of GCA patients, of whom 5 were PET/CT(+) and 3 PET/CT(-) patients. IL-17A(+) NETs were observed in all GCA patients. IL-1ß(+) NETs were not detected in any GCA patient. No relation was found between serum IL-6 and IL-17A levels and NETs containing IL-6 and/or IL-17A. CONCLUSIONS: NETs bearing pro-inflammatory cytokines are present in inflamed GCA-TABs. Future studies with a larger number of patients from different centres will show whether the findings regarding neutrophils/NETs in the TAB are consistent and disclose their clinical impact.

Novel cell-based analysis reveals region-dependent changes in microglial dynamics in grey matter in a cuprizone model of demyelination.

Microglia are key players in Multiple Sclerosis (MS), expressing many susceptibility genes for this disease. They constantly survey the brain microenvironment, but the precise functional relationships between microglia and pathological processes remain unknown. We performed a detailed assessment of microglial dynamics in three distinct grey matter regions in a cuprizone-induced demyelination model. We found that microglial activation preceded detectable demyelination and showed regional specificities, such as prominent phagocytic activity in cortical layer 5 and early hypertrophic morphology in hippocampal CA1. Demyelination happened earliest in cortical layer 5, although was more complete in CA1. In cortical layer 2/3, microglial activation and demyelination were less pronounced but microglia became hyper-ramified with slower process movement during remyelination, thereby maintaining local brain surveillance. Profiling of microglia using specific morphological and motility parameters revealed region-specific heterogeneity of microglial responses in the grey matter that might serve as sensitive indicators of progression in CNS demyelinating diseases.

Exploiting the Role of Hypoxia-Inducible Factor 1 and Pseudohypoxia in the Myelodysplastic Syndrome Pathophysiology.

Myelodysplastic syndromes (MDS) comprise a heterogeneous group of clonal hematopoietic stem (HSCs) and/or progenitor cells disorders. The established dependence of MDS progenitors on the hypoxic bone marrow (BM) microenvironment turned scientific interests to the transcription factor hypoxia-inducible factor 1 (HIF-1). HIF-1 facilitates quiescence maintenance and regulates differentiation by manipulating HSCs metabolism, being thus an appealing research target. Therefore, we examine the aberrant HIF-1 stabilization in BMs from MDS patients and controls (CTRLs). Using a nitroimidazole-indocyanine conjugate, we show that HIF-1 aberrant expression and transcription activity is oxygen independent, establishing the phenomenon of pseudohypoxia in MDS BM. Next, we examine mitochondrial quality and quantity along with levels of autophagy in the differentiating myeloid lineage isolated from fresh BM MDS and CTRL aspirates given that both phenomena are HIF-1 dependent. We show that the mitophagy of abnormal mitochondria and autophagic death are prominently featured in the MDS myeloid lineage, their severity increasing with intra-BM blast counts. Finally, we use in vitro cultured CD34+ HSCs isolated from fresh human BM aspirates to manipulate HIF-1 expression and examine its potential as a therapeutic target. We find that despite being cultured under 21% FiO2, HIF-1 remained aberrantly stable in all MDS cultures. Inhibition of the HIF-1α subunit had a variable beneficial effect in all <5%-intra-BM blasts-MDS, while it had no effect in CTRLs or in ≥5%-intra-BM blasts-MDS that uniformly died within 3 days of culture. We conclude that HIF-1 and pseudohypoxia are prominently featured in MDS pathobiology, and their manipulation has some potential in the therapeutics of benign MDS.

Increased autophagy/mitophagy levels in primary tumours of patients with pancreatic neuroendocrine neoplasms.

BACKGROUND/AIMS: We assessed the levels of autophagy and mitophagy, that are linked to cancer development and drug resistance, in well differentiated pancreatic neuroendocrine neoplasms (PanNENs) and correlated them with clinico-pathological parameters. METHODS: Fluorescent immunostaining for the autophagy markers LC3Β and p62/or LAMP1 was performed on 22 PanNENs and 11 controls of normal pancreatic tissues and validated through Western blotting. Autophagy quantitative scoring was generated for LC3B-positive puncta and analysed in relation to clinico-pathological parameters. TOMM20/LC3B qualitative assessment of mitophagy levels was undertaken by fluorescent immunostaining. The presence of autophagy/mitophagy was validated by transmission electron microscopy. RESULTS: Autophagy levels (LC3B-positive puncta/cell) were discriminative for normal vs. NEN pancreatic tissue (p = 0.007). A significant association was observed between autophagy levels and tumour grade (Ki67 < 3% vs. Ki67 ≥ 3%; p = 0.021), but not functionality (p = 0.266) size (cut-off of 20 mm; p = 0.808), local invasion (p = 0.481), lymph node- (p = 0.849) and distant metastases (p = 0.699). Qualitative assessment of TOMM20/LC3B demonstrated strong mitophagy levels in PanNENs by fluorescent immunostaining as compared with normal tissue. Transmission electron microscopy revealed enhanced autophagy and mitophagy in PanNEN tissue. Response to molecular targeted therapies in metastatic cases (n = 4) did not reveal any patterns of association to autophagy levels. CONCLUSIONS: Increased autophagy levels are present in primary tumours of patients with PanNENs and are partially attributed to upregulated mitophagy. Grade was the only clinico-pathological parameter associated with autophagy scores.

Combining RANK/RANKL and ERBB-2 targeting as a novel strategy in ERBB-2-positive breast carcinomas.

BACKGROUND: ERBB-2 is overexpressed in about 20% of breast cancers (BCs), indicating poor prognosis. The receptor activator of nuclear factor-κB (RANK) pathway is implicated in ERBB-2 (+) BC. The purpose of this study was to elucidate the underlying molecular mechanism of this interaction and the beneficial impact of dual targeting of RANK and ERBB-2 pathways. METHODS: We used SKBR3, MCF7, MDA-MB-453, and BT-474 human BC cell lines. We examined RANK and RANKL expression using RT-PCR, Western blot, and immunofluorescence. The evaluation of RANK expression in a cohort of BC patients was performed using immunohistochemistry. The interaction between RANK and ERBB family members was detected using proximity ligation assay (PLA), which enables the visualization of interacting proteins. We used inhibitors of both pathways [trastuzumab (T), pertuzumab (P), denosumab (D)]. NF-κB pathway activation was studied using Western blot. Cell growth and viability was evaluated using XTT, flow cytometry, and clonogenic assay. For cell migration evaluation, scratch assay was performed. Data were analyzed by one-way ANOVA. RESULTS: Cell lines express RANK and RANKL. RANK immunostaining was also detected in human BC tissue samples. RANK receptor dimerizes with ERBB family members. RANK/ERBB-2 dimer number seems to be associated with ERBB-2 expression (SKBR3, 5.4; BT-474, 8.2; MCF7, 0.7; MDA-MB-453, 0.3). RANK/ERBB-2 dimers were decreased in the presence of the inhibitors D, T, and P, while they were increased after RANKL (R) treatment in SKBR3 (m, 5.4; D, 1.2; T, 1.9; DT, 0.6; TP, 1; DTP, 0.4; R, 11.8) and BT-474 (m, 8.2; D, 3.1; T, 4.3; DT, 0.7; TP, 3.4; DTP, 3.2; R, 11.6). Combination targeting of SKBR3 further decreased NF-κB pathway activation compared to single targeting. In SKBR3, RANKL and ERBB-2 blockage resulted in reduced cell proliferation, increased apoptosis, and lower metastatic potential compared to mock cells (m) and reversed values in RANKL presence. The combination treatment of SKBR3 with D, T, and P had an advantage in functional traits compared to single targeting. Denosumab suppressed NF-κB signaling and diminished proliferation rate in MDA-MB-453 cells. MCF7 did not correspond to inhibitors. CONCLUSIONS: The results indicate a novel physical and molecular association between ERBB-2 and RANK pathways that affects ERBB-2 (+) BC growth. We also present data suggesting that the combination of anti-ERBB-2 agents and RANKL inhibitors have a potential direct anti-tumor effect and should be further tested in certain BC patients.

Estrogen receptor beta increases sensitivity to enzalutamide in androgen receptor-positive triple-negative breast cancer.

PURPOSE: Androgen receptor (AR) is playing an important role in the progression of a subset of TNBC. We evaluated the impact of ERß expression along with anti-AR drugs in AR-positive TNBC. METHODS: ERß expression was examined in AR-positive TNBC cell line using MTT assay, scratch and Annexin V-FITC assay in the presence or absence of anti-androgens. Protein levels of involved molecules were assessed using Western blot. Receptors' localization was detected by immunofluorescence and their physical association was examined using proximity ligation assay (PLA), which enables the visualization of interacting proteins in fixed cells and tissues. RESULTS: Transient transfection of ERß in MDA-MB 453 AR-positive TNBC cell line significantly inhibited cell proliferation, metastatic potential and induced apoptosis. ERß expression reversed the aggravating role of AR in both indirect and direct ways. Indirectly, ERß decreased AR activation through the inhibition of PI3K/AKT signaling pathway. Directly, ERß formed heterodimers with AR in MDA-MB 453 cells and in human tissue samples impeding AR from forming homodimers. Enzalutamide is a more potent anti-androgen in AR + TNBC compared to bicalutamide. ERß expression increased the sensitivity of MDA-MB 453 cells to anti-androgens and especially to enzalutamide. The administration of enzalutamide enhanced AR:ERß heterodimers formation increasing the anti-tumor capacity of ERß. CONCLUSIONS: Collectively, our results provide evidence for a novel mechanism by which ERß exerts oncosuppressive effect in AR-positive TBNC through direct and indirect interactions with AR. Moreover, ERß expression may identify a new subset of TNBC that would respond more favorable to anti-androgens.

Systemic activation of NLRP3 inflammasome in patients with severe primary Sjögren's syndrome fueled by inflammagenic DNA accumulations.

Sjögren's syndrome (SS) patients manifest high cell-free DNA (cf-DNA) levels in serum, associated with impaired DNaseI activity. Undegraded DNA may accumulate in tissues and act as an inflammasome-activating signal. Herein, we investigated the occurrence of aberrant DNA build-up in various biologic compartments of SS patients and its correlation with the activity of NLRP3 and AIM2 inflammasomes. For this purpose, we evaluated sera, PBMC, circulating monocytes and salivary glands (SG) from different SS patient subgroups and controls. We found that SS patients at high risk for lymphoma and those with established lymphoma display high serum cf-DNA levels, substantial extranuclear DNA accumulations in PBMC and SG tissues, a unique NLRP3 inflammasome gene signature in PBMC, and significantly increased serum IL-18 and ASC levels. In these patients, the circulating monocytes manifested NLRP3 inflammasome activation and increased response to NLRP3 stimuli, whereas SG-infiltrating macrophages exhibited signs of NLRP3 activation and pyroptosis. Cell-free nucleic acids isolated from patients' sera competently primed the activation of both NLRP3 and AIM2 inflammasomes in healthy monocytes. SS patients also manifested diminished DNaseI activity in serum and DNaseII expression in PBMC, which inversely correlated with indices of inflammasome activation. DNaseII gene-silencing in healthy monocytes led to cytoplasmic DNA deposition and activation of inflammasome-related genes and of caspase1. Our data reveal the occurrence of systemic NLRP3 inflammasome activation in severe SS, which is associated with widespread extranuclear accumulations of inflammagenic DNA and impaired DNA degradation. These findings can provide novel biomarkers and new therapeutic targets for the management of SS patients with adverse outcomes.

Neural stem/progenitor cells differentiate into oligodendrocytes, reduce inflammation, and ameliorate learning deficits after transplantation in a mouse model of traumatic brain injury.

The central nervous system has limited capacity for regeneration after traumatic injury. Transplantation of neural stem/progenitor cells (NPCs) has been proposed as a potential therapeutic approach while insulin-like growth factor I (IGF-I) has neuroprotective properties following various experimental insults to the nervous system. We have previously shown that NPCs transduced with a lentiviral vector for IGF-I overexpression have an enhanced ability to give rise to neurons in vitro but also in vivo, upon transplantation in a mouse model of temporal lobe epilepsy. Here we studied the regenerative potential of NPCs, IGF-I-transduced or not, in a mouse model of hippocampal mechanical injury. NPC transplantation, with or without IGF-I transduction, rescued the injury-induced spatial learning deficits as revealed in the Morris Water Maze. Moreover, it had beneficial effects on the host tissue by reducing astroglial activation and microglial/macrophage accumulation while enhancing generation of endogenous oligodendrocyte precursor cells. One or two months after transplantation the grafted NPCs had migrated towards the lesion site and in the neighboring myelin-rich regions. Transplanted cells differentiated toward the oligodendroglial, but not the neuronal or astrocytic lineages, expressing the early and late oligodendrocyte markers NG2, Olig2, and CNPase. The newly generated oligodendrocytes reached maturity and formed myelin internodes. Our current and previous observations illustrate the high plasticity of transplanted NPCs which can acquire injury-dependent phenotypes within the host CNS, supporting the fact that reciprocal interactions between transplanted cells and the host tissue are an important factor to be considered when designing prospective cell-based therapies for CNS degenerative conditions.

6-Br-5methylindirubin-3'oxime (5-Me-6-BIO) targeting the leishmanial glycogen synthase kinase-3 (GSK-3) short form affects cell-cycle progression and induces apoptosis-like death: exploitation of GSK-3 for treating leishmaniasis.

Indirubins known to target mammalian cyclin-dependent kinases (CDKs) and glycogen synthase kinase (GSK-3) were tested for their antileishmanial activity. 6-Br-indirubin-3'-oxime (6-BIO), 6-Br-indirubin-3'acetoxime and 6-Br-5methylindirubin-3'oxime (5-Me-6-BIO) were the most potent inhibitors of Leishmania donovani promastigote and amastigote growth (half maximal inhibitory concentration (IC(50)) values < or =1.2 microM). Since the 6-Br substitution on the indirubin backbone greatly enhances the selectivity for mammalian GSK-3 over CDKs, we identified the leishmanial GSK-3 homologues, a short (LdGSK-3s) and a long one, focusing on LdGSK-3s which is closer to human GSK-3beta, for further studies. Kinase assays showed that 5-Me-6-BIO inhibited LdGSK-3s more potently than CRK3 (the CDK1 homologue in Leishmania), whilst 6-BIO was more selective for CRK3. Promastigotes treated with 5-Me-6-BIO accumulated in the S and G2/M cell-cycle phases and underwent apoptosis-like death. Interestingly, these phenotypes were completely reversed in parasites over-expressing LdGSK-3s. This finding strongly supports that LdGSK-3s is: (i) the intracellular target of 5-Me-6-BIO, and (ii) involved in cell-cycle control and in pathways leading to apoptosis-like death. 6-BIO treatment induced a G2/M arrest, consistent with inhibition of CRK3 and apoptosis-like death. These effects were partially reversed in parasites over-expressing LdGSK-3s suggesting that in vivo 6-BIO may also target LdGSK-3s. Molecular docking of 5-Me-6-BIO in CRK3 and 6-BIO in human GSK-3beta and LdGSK-3s active sites predict the existence of functional/structural differences that are sufficient to explain the observed difference in their affinity. In conclusion, LdGSK-3s is validated as a potential drug target in Leishmania and could be exploited for the development of selective indirubin-based leishmanicidals.

In vitro activity of 10-deacetylbaccatin III against Leishmania donovani promastigotes and intracellular amastigotes.

Current treatments for leishmaniasis are unsatisfactory due to their route of administration, toxicity and expense but, most importantly, to the developed resistance of Leishmania to first-line drugs. Therefore, the identification of new effective targeted drugs is an urgent need. Since many studies have shown that medicinal plants contain compounds active against protozoa we have undertaken a study aiming to determine the antileishmanial activity of the taxoid 10-deacetylbaccatin III, isolated from dried needles and small branches of the European yew tree (Taxus baccata). Interestingly, 10-deacetylbaccatin III was found to selectively inhibit the growth of L. DONOVANI intracellular amastigotes within J774 murine macrophages in vitro at nanomolar concentrations with an IC(50) value of 70 nM. Concentrations of 10-deacetylbaccatin III as high as 5 microM did not affect J774 murine macrophages whereas 20 nM of taxol, used as a control, was toxic to macrophages. The compound also inhibited the growth of L. donovani promastigotes but at higher concentrations with a maximum level of inhibition of 35 %. Taxol inhibited promastigote growth at micromolar concentrations. Comparison of the effect of 10-deacetylbaccatin III to that of taxol on cell cycle progression and cellular morphology showed that their mechanisms of action are different. The 10-deacetylbaccatin III-treated promastigotes were slightly arrested in the G2/M phase whereas taxol-treated cells were blocked in the G2/M phase. In addition 10-deacetylbaccatin III treatment, contrary to taxol, did not affect cellular morphology.

Leishmania histone H1 overexpression delays parasite cell-cycle progression, parasite differentiation and reduces Leishmania infectivity in vivo.

Episomal expression of Leishmania histone H1 sense mRNAs in Leishmania major promastigotes was found previously to result in overexpression of this molecule and to reduce parasite infectivity in vitro. Herein, we evaluated the in vivo infectivity of these transfectants, in BALB/c mice, and showed that it is dramatically reduced. No lesions were observed in this group of mice and this was associated with an extremely low number of parasites both in the footpad and in the draining lymph nodes. Interestingly, the transfectants-reduced infectivity was associated with a delay in their cell-cycle progression and differentiation to axenic amastigotes, assessed in vitro. Therefore, the dramatic reduction in their infectivity may be attributed to the above-mentioned phenotypic modifications. As the metazoan linker histone H1(0) homologue is known to delay cell-cycle progression in mammalian cells we investigated whether its Leishmania counterpart, which possesses homology to its C-terminal region, when expressed in mammalian cells may also affect their cell-cycle progression. It was thus shown that Leishmania histone H1 expressed in COS7 and NIH 3T3 cells, delays cell-cycle progression in these cells too. The latter strengthens the phenotype observed in Leishmania and provides evidence that critical functions of histone H1 molecules are conserved throughout evolution.