A New Immunomodulatory Role for Peroxisomes in Macrophages Activated by the TLR4 Ligand Lipopolysaccharide

Abstract

Peroxisomes are proposed to play an important role in the regulation of systemic inflammation; however, the functional role of these organelles in inflammatory responses of myeloid immune cells is largely unknown. In this article, we demonstrate that the nonclassical peroxisome proliferator 4-phenyl butyric acid is an efficient inducer of peroxisomes in various models of murine macrophages, such as primary alveolar and peritoneal macrophages and the macrophage cell line RAW264.7, but not in primary bone marrow-derived macrophages. Further, proliferation of peroxisomes blocked the TLR4 ligand LPS-induced proinflammatory response, as detected by the reduced induction of the proinflammatory protein cyclooxygenase (COX)-2 and the proinflammatory cytokines TNF-α, IL-6, and IL-12. In contrast, disturbing peroxisome function by knockdown of peroxisomal gene or markedly increased the LPS-dependent upregulation of the proinflammatory proteins COX-2 and TNF-α. Specifically, induction of peroxisomes did not affect the upregulation of COX-2 at the mRNA level, but it reduced the half-life of COX-2 protein, which was restored by COX-2 enzyme inhibitors but not by proteasomal and lysosomal inhibitors. Liquid chromatography-tandem mass spectrometry analysis revealed that various anti-inflammatory lipid mediators (e.g., docosahexaenoic acid) were increased in the conditioned medium from peroxisome-induced macrophages, which blocked LPS-induced COX-2 upregulation in naive RAW264.7 cells and human primary peripheral blood-derived macrophages. Importantly, LPS itself induced peroxisomes that correlated with the regulation of COX-2 during the late phase of LPS activation in macrophages. In conclusion, our findings identify a previously unidentified role for peroxisomes in macrophage inflammatory responses and suggest that peroxisomes are involved in the physiological cessation of macrophage activation.

HSD17B4, ACAA1, and PXMP4 in Peroxisome Pathway Are Down-Regulated and Have Clinical Significance in Non-small Cell Lung Cancer

“…The genes were applied to enrichment analysis and they were significant enriched in 11 terms (Figure 8B). Interestingly, except peroxisome, several immune-related processes including phagocytosis, regulation of adaptive immune response, regulation of lymphocyte mediated immunity, and ECM affiliated were enriched, consistent with the associations of peroxisomes with immune response and inflammation reported in previous studies (Vijayan et al, 2017;Di Cara et al, 2019), indicating the implication of HSD17B4, ACAA1, and PXMP4 in these processes.…”

Metabolic Reprogramming during Microglia Activation

“…We could speculate that lipid metabolism, fatty acid synthesis and degradation in particular, might support a protective microglia phenotype, which could drive neuroprotection in neurodegenerative diseases. Furthermore, as we previously showed that peroxisomal FAO is a hallmark of M2 macrophages [73], and considering the novel roles of peroxisomes in immune cell functioning [74][75][76][77], it is of importance to also highlight this aspect of metabolism in microglia. In our study, we observed, in contrast to macrophages, no changes in peroxisomal FAO in polarized microglia.…”

Analysis of ketone‐based neurosteroids by reactive low‐temperature plasma mass spectrometry

“…After repeating the extraction and centrifugation twice, the supernatants were combined and diluted with 7 mL of water. For some experiments, the sample was further purified with a polymeric reversed phase SPE cartridge as described previously . Briefly, the cartridge was first equilibrated with 3.5 mL of 100% methanol followed by 3.5 mL of water; then the sample was loaded and washed with 10% methanol; neurosteroids were eluted from the cartridge with 1.5 mL of methanol.…”

“…For some experiments, the sample was further purified with a polymeric reversed phase SPE cartridge as described previously. 47 Briefly, the cartridge was first equilibrated with 3.5 mL of 100% methanol followed by 3.5 mL of water; then the sample was loaded and washed with 10% methanol; neurosteroids were eluted from the cartridge with 1.5 mL of methanol. After evaporating the solvent from the eluate in a nitrogen stream, the residue was reconstituted in 200 μL of methanol.…”