Immune response of BV-2 microglial cells is impacted by peroxisomal beta-oxidation

Microglia are crucial for brain homeostasis, and dysfunction of these cells is a key driver in most neurodegenerative diseases, including peroxisomal leukodystrophies. In X-linked adrenoleukodystrophy (X-ALD), a neuroinflammatory disorder, very long-chain fatty acid (VLCFA) accumulation due to impaired degradation within peroxisomes results in microglial defects, but the underlying mechanisms remain unclear. Using CRISPR/Cas9 gene editing of key genes in peroxisomal VLCFA breakdown (Abcd1, Abcd2, and Acox1), we recently established easily accessible microglial BV-2 cell models to study the impact of dysfunctional peroxisomal β-oxidation and revealed a disease-associated microglial-like signature in these cell lines. Transcriptomic analysis suggested consequences on the immune response. To clarify how impaired lipid degradation impacts the immune function of microglia, we here used RNA-sequencing and functional assays related to the immune response to compare wild-type and mutant BV-2 cell lines under basal conditions and upon pro-inflammatory lipopolysaccharide (LPS) activation. A majority of genes encoding proinflammatory cytokines, as well as genes involved in phagocytosis, antigen presentation, and co-stimulation of T lymphocytes, were found differentially overexpressed. The transcriptomic alterations were reflected by altered phagocytic capacity, inflammasome activation, increased release of inflammatory cytokines, including TNF, and upregulated response of T lymphocytes primed by mutant BV-2 cells presenting peptides. Together, the present study shows that peroxisomal β-oxidation defects resulting in lipid alterations, including VLCFA accumulation, directly reprogram the main cellular functions of microglia. The elucidation of this link between lipid metabolism and the immune response of microglia will help to better understand the pathogenesis of peroxisomal leukodystrophies

Nuclear Control of the Inflammatory Response in Mammals by Peroxisome Proliferator-Activated Receptors

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that play pivotal roles in the regulation of a very large number of biological processes including inflammation. Using specific examples, this paper focuses on the interplay between PPARs and innate immunity/inflammation and, when possible, compares it among species. We focus on recent discoveries establishing how inflammation and PPARs interact in the context of obesity-induced inflammation and type 2 diabetes, mostly in mouse and humans. We illustrate that PPARγ ability to alleviate obesity-associated inflammation raises an interesting pharmacologic potential. In the light of recent findings, the protective role of PPARα and PPARβ/δ against the hepatic inflammatory response is also addressed. While PPARs agonists are well-established agents that can treat numerous inflammatory issues in rodents and humans, surprisingly very little has been described in other species. We therefore also review the implication of PPARs in inflammatory bowel disease; acute-phase response; and central, cardiac, and endothelial inflammation and compare it along different species (mainly mouse, rat, human, and pig). In the light of the data available in the literature, there is no doubt that more studies concerning the impact of PPAR ligands in livestock should be undertaken because it may finally raise unconsidered health and sanitary benefits

Regulation of lipogenic genes in obesity

Lipogenesis describes the process of fatty acid and triglyceride synthesis. Lipogenesis mainly occurs in liver and fat tissue and is under the coordinated control of hormonal, nutritional and transcription factors. Several transcription factors have been identified as critical regulators that mediate the effect of hormones and nutrients on gene transcription. This includes the Sterol Regulatory Element Binding Protein-1c “SREBP-1c”, the CCAAT/Enhancer-Binding Protein-alpha “C/EBPalpha”, the nuclear hormone receptors Liver X Receptors “LXRs”, the Peroxisome Proliferator-Activated Receptor gamma “PPARgamma”, the Estrogen Related Receptor alpha “ERRalpha”. The role of these transcription factors in these processes is reviewed and discussed. Although lipogenesis may appear as an attractive target for pharmacological treatment of obesity, recent insights into the metabolic consequences of non-adipose triglyceride storage has shifted attention to alternative targets

Effects of peroxisome proliferators (PPS) on peroxisome proliferators-activated receptors (PPAR) alpha signaling in three different models of rodents

This thesis illustrates the effects of ciprofibrate and aspirin, which are widely used for their therapeutic properties and also known to induce peroxisome proliferation in rodents, on suckling and adult rats, respectively. Moreover, the same pharmacologic approach was used to highlight defects of thiolase B mutation in knock out mouse. Suckling rats fed by lactating-mothers treated with ciprofibrate showed a strong induction of peroxisomal beta-oxidation activity especially in liver, while catalase activity was weakly up-regulated, confirming a dilution of this enzyme activity, which, in turn, could lead to an oxidative stress. Furthermore, a perturbation on cell proliferation and apoptosis was observed exclusively in liver. So that, this imbalance and the oxidative stress produced by ciprofibrate in suckling rats may mediate the hepatocarcinogenesis, as observed in PP long term administration in adults rats. Treatment of adult rats with aspirin has demonstrated that this drug is able to produce, as expected, a slight induction of some peroxisomal enzymes both in liver and kidney, while no modification on cell proliferation or apoptosis neither during drug treatment nor after withdrawal was observed. The correlation between the peroxisome and cell proliferation is, at present, widely investigated and it is thought that the two phenomena are associated but not closely related. In the last part of this thesis, we studied the characterization of the thiolase B knoch out mouse. At first sight, thiolase B-/- mouse was viable, healthy, fertile and devoid of gross phenotypic defects under basal conditions. The pharmacologic treatment with WY14,643, which induces both expression of the thiolase B and peroxisome proliferation, highlighted some molecular alterations: in particular, it was shown by Affymetrix microarrays that the lack of thiolase B dysregulated the cholesterol biosinthesis, while PPAR alpha signaling was not affected. At physiological level, we did not observe any changes in hepatic cholesterol contents, while a significant increase of plasma triglicerides profile was observed in knoch out mice with respect to the wild type.Cette thèse illustre dans la première partie les effets du ciprofibrate et de l'aspirine (qui sont largement utilisés pour leurs propriétés thérapeutiques et aussi connues pour induire la prolifération de peroxysomes chez les rongeurs) dans rats nourrissons et rats adultes, respectivement. Par ailleurs, la même approche pharmacologique a permis de mettre en évidence, dans la seconde partie de cette thèse, les défauts des souris mutants pour la 3-cétoacyl-CoA Thiolase B (ThB) de peroxysomes. Rats nourrissons nourris par des mères traitées avec ciprofibrate montrent une forte induction de l activité de beta-oxydation de peroxysome surtout dans le foie, tandis que l'activité de la catalase a été faiblement up-regulated, confirmant ainsi une dilution de cette dernière activité que, à son tour, pourrait conduire à un stress oxydatif. En outre, une perturbation sur la prolifération cellulaire et l'apoptose a été observée uniquement dans le foie. Alors que, ce déséquilibre et le stress oxydatif produit par le ciprofibrate dans les rats nourrissons peut produire la tumeur du foie, comme a été observé dans les rats adultes traités pour une période très long. Le traitement des rats adultes avec de l'aspirine a démontré que ce médicament est capable de produire, comme prévu, une légère induction de certaines enzymes de peroxysomes dans le foie et les reins, tandis que aucune modification sur la prolifération cellulaire ou sur l'apoptose ni pendant ni après traitement a été observée. La corrélation entre la prolifération cellulaire et prolifération de peroxysomes est, actuellement, largement étudiée et on pense que les deux phénomènes sont liés, mais pas strictement liées. Dans la dernière partie de cette thèse, nous avons étudié la caractérisation de la souris déficiente pour la thiolase B. A première vue, la souris déficiente pour la ThB était viable, saine, fertile et sans gros défauts phénotypiques dans les conditions basales. Le traitement pharmacologique avec WY 14,643, ce qui induit l expression de la thiolase B dans le fois et de la prolifération de peroxysomes, a mis en évidence certaines altérations moléculaires: en particulier, en utilisant des puces à ADN a été montré que le manque de ThB dysrégulation la biosynthèse du cholestérol, tandis que la voie de signalisation contrôlée par PPAR alpha n est pas affectée. Au niveau physiologique, nous n'avons pas observé de changements dans le cholestérol contenu dans le foie, alors qu'une augmentation significative des concentrations plasmatiques de triglycérides a été observée chez les souris déficiente pour la ThB par rapport au type sauvage.DIJON-BU Sciences Economie (212312102) / SudocSudocFranceF

Physiological and Nutritional Roles of PPAR across Species

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Nuclear Localization of a New C-Cbl Related Protein, Carp 90, During in Vivo Thymic Apoptosis in Mice

This study investigates the involvement of the c-cbl protooncogene in thymocyte apoptosis occurring in vivo after hydrocortisone treatment. In the thymus of untreated mice, a few medullary and cortical thymocytes expressed p120cbl, mainly in the cytoplasm. In the cortex, their number and distribution resemble that of apoptotic cells evidenced by TUNEL staining. The expression of Cbl is rapidly increased when apoptosis is triggered by hydrocortisone. This Cbl-specific immunostaining was detected in the nucleus and is due to a Cbl-related 90 kDa protein (CARP 90). These results show that a c-cbl product could localize in the nucleus and suggest that it could be involved as a regulator of thymic apoptosis

Lipopolysaccharides-mediated increase in glucose-stimulated insulin secretion: Involvement of the glucagon-like peptide 1 (GLP1) pathway.

International audienceLipopolysaccharides (LPS) of the cell wall of Gram (-) bacteria trigger inflammation, which is associated with marked changes in glucose metabolism. Hyperglycemia is frequently observed during bacterial infection and it is a marker of a poor clinical outcome in critically ill patients. The aim of the present study was to investigate the effect of an acute injection or continuous infusion of LPS on experimentally-induced hyperglycemia in wild-type and genetically-engineered mice. The acute injection of a single dose of LPS produced an increase in glucose disposal and glucose-stimulated insulin secretion (GSIS). Continuous infusion of LPS through mini-osmotic pumps was also associated with increased GSIS. Finally, manipulation of LPS detoxification by knocking out the plasma phospholipid transfer protein (PLTP) led to increased glucose disposal and GSIS. Overall, glucose tolerance and GSIS tests supported the hypothesis that mice treated with LPS develop glucose-induced hyperinsulinemia. The effects of LPS on glucose metabolism were significantly altered as a result of either the accumulation or antagonism of glucagon-like peptide 1 (GLP1). Complementary studies in wild-type and GLP1-R knockout mice further implicated the GLP1R-dependent pathway in mediating the LPS-mediated changes in glucose metabolism. Hence, enhanced GLP1 secretion and action underlies the development of glucose-mediated hyperinsulinemia associated with endotoxemia

Phospholipid transfer protein (PLTP), lipopolysaccharides detoxification and metabolic diseases: a connection ?

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