Lipopolysaccharide Stimulus Research Articles

Aldose reductase deficiency inhibits LPS-induced M1 response in macrophages by activating autophagy

Macrophage M1 polarization mediates inflammatory responses and tissue damage. Recently, aldose reductase (AR) has been shown to play a critical role in M1 polarization in macrophages. However, the underlying mechanisms are unknown. Here, we demonstrated, for the first time, that AR deficiency repressed the induction of inducible nitric oxide synthase in lipopolysaccharide (LPS)-stimulated macrophages via activation of autophagy. This suppression was related to a defect in the inhibitor of nuclear factor κB (NF-κB) kinase (IKK) complex in the classical NF-κB pathway. However, the mRNA levels of IKKβ and IKKγ were not reduced in LPS-treated AR knockout (KO) macrophages, indicating that their proteins were downregulated at the post-transcriptional level. We discovered that LPS stimuli induced the recruitment of more beclin1 and increased autophagosome formation in AR-deficient macrophages. Blocking autophagy through 3-methyladenine and ammonium chloride treatment restored IKKβ and IKKγ protein levels and increased nitric oxide synthase production in LPS-stimulated AR-deficient macrophages. More assembled IKKβ and IKKγ underwent ubiquitination and recruited the autophagic adaptor p62 in LPS-induced AR KO macrophages, promoting their delivery to autophagosomes and lysosomes. Collectively, these findings suggest that AR deficiency is involved in the regulation of NF-κB signaling, and extends the role of selective autophagy in fine-tuned M1 macrophage polarization.

Microglia activated by microbial neuraminidase contributes to ependymal cell death

The administration of microbial neuraminidase into the brain ventricular cavities of rodents represents a model of acute aseptic neuroinflammation. Ependymal cell death and hydrocephalus are unique features of this model. Here we demonstrate that activated microglia participates in ependymal cell death. Co-cultures of pure microglia with ependymal cells (both obtained from rats) were performed, and neuraminidase or lipopolysaccharide were used to activate microglia. Ependymal cell viability was unaltered in the absence of microglia or inflammatory stimulus (neuraminidase or lipopolysaccharide). The constitutive expression by ependymal cells of receptors for cytokines released by activated microglia, such as IL-1β, was demonstrated by qPCR. Besides, neuraminidase induced the overexpression of both receptors in ventricular wall explants. Finally, ependymal viability was evaluated in the presence of functional blocking antibodies against IL-1β and TNFα. In the co-culture setting, an IL-1β blocking antibody prevented ependymal cell death, while TNFα antibody did not. These results suggest that activated microglia are involved in the ependymal damage that occurs after the administration of neuraminidase in the ventricular cavities, and points to IL-1β as possible mediator of such effect. The relevance of these results lies in the fact that brain infections caused by neuraminidase-bearing pathogens are frequently associated to ependymal death and hydrocephalus.

Olodaterol exerts anti-inflammatory effects on COPD airway epithelial cells

BackgroundAirway inflammation is a key feature of chronic obstructive pulmonary disease (COPD) and inhaled corticosteroids (ICS) remain the main treatment for airway inflammation. Studies have noted the increased efficacy of ICS and long-acting beta 2 agonist (LABA) combination therapy in controlling exacerbations and improving airway inflammation than either monotherapy. Further studies have suggested that LABAs may have inherent anti-inflammatory potential, but this has not been well-studied.ObjectiveWe hypothesize that the LABA olodaterol can inhibit airway inflammation resulting from exposure to respiratory syncytial virus (RSV) via its binding receptor, the β2-adrenergic receptor.MethodsHuman bronchial epithelial brushing from patients with and without COPD were cultured into air–liquid interface (ALI) cultures and treated with or without olodaterol and RSV infection to examine the effect on markers of inflammation including interleukin-8 (IL-8) and mucus secretion. The cell line NCI-H292 was utilized for gene silencing of the β2-adrenergic receptor via siRNA as well as receptor blocking via ICI 118,551 and butaxamine.ResultsAt baseline, COPD-ALIs produced greater amounts of IL-8 than control ALIs. Olodaterol reduced RSV-mediated IL-8 secretion in both COPD and control ALIs and also significantly reduced Muc5AC staining in COPD-ALIs infected with RSV. A non-significant reduction was seen in control ALIs. Gene silencing of the β2-adrenergic receptor in NCI-H292 negated the ability of olodaterol to inhibit IL-8 secretion from both RSV infection and lipopolysaccharide stimulus, as did blocking of the receptor with ICI 118,551 and butaxamine.ConclusionsOlodaterol exhibits inherent anti-inflammatory properties on the airway epithelium, in addition to its bronchodilation properties, that is mediated through the β2-adrenergic receptor and independent of ICS usage.

The influence of the R47H triggering receptor expressed on myeloid cells 2 variant on microglial exosome profiles.

Variants in the triggering receptor expressed on myeloid cells 2 gene are linked with an increased risk of dementia, in particular the R47Hhet triggering receptor expressed on myeloid cells 2 variant is linked to late-onset Alzheimer’s disease. Using human induced pluripotent stem cells-derived microglia, we assessed whether variations in the dynamics of exosome secretion, including their components, from these cells might underlie some of this risk. We found exosome size was not altered between common variant controls and R47Hhet variants, but the amount and constitution of exosomes secreted were different. Exosome quantities were rescued by incubation with an ATP donor or with lipids via a phosphatidylserine triggering receptor expressed on myeloid cells 2 ligand. Following a lipopolysaccharide or phagocytic cell stimulus, exosomes from common variant and R47Hhet microglia were found to contain cytokines, chemokines, APOE and triggering receptor expressed on myeloid cells 2. Differences were observed in the expression of CCL22, IL-1β and triggering receptor expressed on myeloid cells 2 between common variant and R47Hhet derived exosomes. Furthermore unlike common variant-derived exosomes, R47Hhet exosomes contained additional proteins linked to negative regulation of transcription and metabolic processes. Subsequent addition of exosomes to stressed neurones showed R47Hhet-derived exosomes to be less protective. These data have ramifications for the responses of microglia in Alzheimer’s disease and may point to further targets for therapeutic intervention.

6-Formylindolo[3,2-b]carbazole alleviates lipopolysaccharide-induced acute lung injury via suppressing endoplasmic reticulum stress

To investigate the effect and mechanism of 6-formylindolo[3,2-b]carbazole (FICZ) on lipopolysaccharide (LPS)-induced acute lung injury (ALI) in mice. Male C57BL/6J mice aged 8-12 weeks were divided into 4 groups with 8 mice in each group, according to the method of simple random sampling. Sepsis-induced ALI mice model was established by intraperitoneal injection of LPS 5 mg/kg (LPS group), and phosphate buffer saline (PBS) control group (PBS group) was injected with equal volume of PBS. The LPS+FICZ group was intervened by intraperitoneal injection of 1 μg FICZ 1 hour after LPS stimuli, while the FICZ control group (FICZ group) was given the same amount of FICZ 1 hour after intraperitoneal injection of PBS. Serum and lung tissue were collected 24 hours after LPS stimuli, and the pathological changes of lung tissue were analyzed by hematoxylin-eosin (HE) staining and wet/dry weight (W/D) ratio of lung tissue. The concentrations of inflammatory factors in serum and lung tissue were detected by enzyme linked immunosorbent assay (ELISA). The expression levels of endoplasmic reticulum stress signaling pathway related molecules were detected by real-time fluorescent quantitative polymerase chain reaction (RT-qPCR) and Western blotting. Compared with PBS group, inflammatory cell infiltration, alveolar collapse and obvious alveolar exudative lesions had increased, lung tissue W/D ratio was significantly increased, serum interleukin-6 (IL-6) level, lung tissue IL-6 mRNA expression, and the mRNA expressions of glucose-regulated protein 78 (GRP78), protein kinase R-like endoplasmic reticulum kinase (PERK), CCAAT/EBP homologous protein (CHOP), and the protein expressions of GRP78, PERK, activating transcription factor 6 (ATF6), CHOP in lung tissue were significantly increased in LPS group. However, the indexes of FICZ group were not affected. Compared with LPS group, LPS+FICZ group had less inflammatory cell infiltration, relatively intact alveolar structure. Lung W/D weight ratio in LPS+FICZ group was significantly decreased (5.38±0.10 vs. 6.60±0.30, P < 0.01), so as serum IL-6 (ng/L: 15.55±3.77 vs. 32.22±3.84) and lung IL-6 mRNA expression (2-ΔΔCt: 0.79±0.21 vs. 6.89±0.92, both P < 0.01). The mRNA expressions of GRP78, PERK and CHOP were also significantly decreased [GRP78 mRNA (2-ΔΔCt): 1.90±0.16 vs. 7.55±1.29, PERK mRNA (2-ΔΔCt): 1.68±0.20 vs. 4.54±0.89, CHOP mRNA (2-ΔΔCt): 1.13±0.24 vs. 4.44±1.13, all P < 0.05], and the protein expressions of GRP78, PERK, ATF6 and CHOP were significantly decreased (GRP78/GAPDH: 0.59±0.02 vs. 0.77±0.01, PERK/GAPDH: 0.48±0.03 vs. 1.04±0.05, ATF6/GAPDH: 0.51±0.03 vs. 0.65±0.01, CHOP/GAPDH: 0.91±0.05 vs. 1.11±0.07, all P < 0.05). FICZ protects LPS-induced ALI possibly via suppressing endoplasmic reticulum stress and reducing IL-6 expression in blood and lung tissue.

Unraveling the characterization of minichromosome maintenance complex component 2 (MCM2) gene and its SNPs associated with cold-tolerance trait in Pacific white shrimp (Litopenaeus vannamei)

Minichromosome maintenance complex component 2 (MCM2) plays an important role in DNA replication induced by cold stress. In this study, MCM2 cDNA and genomic DNA (gDNA) sequences were isolated from Pacific white shrimp (Litopenaeus vannamei), and the gene was designated Lv-MCM2. The full-length Lv-MCM2 cDNA was 3,138 bp in length, with an open reading frame (ORF) of 2,721 bp encoding 906 amino acids. The Lv-MCM2 gDNA sequence was 7,322 bp in length and consisted of 16 coding segments in the L. vannamei genome. The expression of Lv-MCM2 mRNA was detected in all selected tissues, with the highest levels being observed in the stomach and gills of the shrimp. The transcript levels of Lv-MCM2 in the stomach and gills were found to be significantly affected by low-temperature, high-pH, low-pH, poly(I:C), and lipopolysaccharide (LPS) stimuli, indicating that Lv-MCM2 might play roles in coping with various stresses. Specifically, under low-temperature stress (13 °C), the knockdown of Lv-MCM2 with siRNA significantly decreased the shrimp survival rate, indicating its key roles in the response to low-temperature stress. Additionally, four single-nucleotide polymorphisms (SNPs) in the Lv-MCM2 gene were identified as being significantly associated (P < 0.001) with the cold tolerance trait in a full-sib family of L. vannamei. Our study suggests that the Lv-MCM2 gene itself or closely linked genes might play important roles in the cold tolerance trait in L. vannamei, and the SNPs from the Lv-MCM2 gene provide a basis for developing molecular markers for breeding cold-tolerant Pacific white shrimp seeds in the future.

Intravenous transplantation of olfactory ensheathing cells reduces neuroinflammation after spinal cord injury via interleukin-1 receptor antagonist.

Rationale: Olfactory ensheathing cell (OEC) transplantation has emerged as a promising therapy for spinal cord injury (SCI) repair. In the present study, we explored the possible mechanisms of OECs transplantation underlying neuroinflammation modulation.Methods: Spinal cord inflammation after intravenous OEC transplantation was detected in vivo and ex vivo by translocator protein PET tracer [18F]F-DPA. To track transplanted cells, OECs were transduced with enhanced green fluorescent protein (eGFP) and HSV1-39tk using lentiviral vector and were monitored by fluorescence imaging and [18F]FHBG study. Protein microarray analysis and ELISA studies were employed to analyze differential proteins in the injured spinal cord after OEC transplantation. The anti-inflammation function of the upregulated protein was also proved by in vitro gene knocking down experiments and OECs/microglia co-culture experiment.Results: The inflammation in the spinal cord was decreased after OEC intravenous transplantation. The HSV1-39tk-eGFP-transduced OECs showed no accumulation in major organs and were found at the injury site. After OEC transplantation, in the spinal cord tissues, the interleukin-1 receptor antagonist (IL-1Ra) was highly upregulated while many chemokines, including pro-inflammatory chemokines IL-1α, IL-1β were downregulated. In vitro studies confirmed that lipopolysaccharide (LPS) stimulus triggered OECs to secrete IL-1Ra. OECs significantly suppressed LPS-stimulated microglial activity, whereas IL-1Ra gene knockdown significantly reduced their ability to modulate microglial activity.Conclusion: The OECs that reached the lesion site were activated by the release of pro-inflammatory cytokines from activated microglia in the lesion site and secreted IL-1Ra to reduce neuroinflammation. Intravenous transplantation of OECs has high therapeutic effectiveness for the treatment of SCI via the secretion of IL-1Ra to reduce neuroinflammation.

Gold nanoparticles (AuNPs) impair LPS-driven immune responses by promoting a tolerogenic-like dendritic cell phenotype with altered endosomal structures.

Dendritic cells (DCs) shape immune responses by influencing T-cell activation. Thus, they are considered both an interesting model for studying nano-immune interactions and a promising target for nano-based biomedical applications. However, the accentuated ability of nanoparticles (NPs) to interact with biomolecules may have an impact on DC function that poses an unexpected risk of unbalanced immune reactions. Here, we investigated the potential effects of gold nanoparticles (AuNPs) on DC function and the consequences for effector and memory T-cell responses in the presence of the microbial inflammatory stimulus lipopolysaccharide (LPS). Overall, we found that, in the absence of LPS, none of the tested NPs induced a DC response. However, whereas 4-, 8-, and 11 nm AuNPs did not modulate LPS-dependent immune responses, 26 nm AuNPs shifted the phenotype of LPS-activated DCs toward a tolerogenic state, characterized by downregulation of CD86, IL-12 and IL-27, upregulation of ILT3, and induction of class E compartments. Moreover, this DC phenotype was less proficient in promoting Th1 activation and central memory T-cell proliferation. Taken together, these findings support the perception that AuNPs are safe under homeostatic conditions; however, particular care should be taken in patients experiencing a current infection or disorders of the immune system.

The long non-coding RNA LUCAT1 is a negative feedback regulator of interferon responses in humans

Long non-coding RNAs are important regulators of biological processes including immune responses. The immunoregulatory functions of lncRNAs have been revealed primarily in murine models with limited understanding of lncRNAs in human immune responses. Here, we identify lncRNA LUCAT1 which is upregulated in human myeloid cells stimulated with lipopolysaccharide and other innate immune stimuli. Targeted deletion of LUCAT1 in myeloid cells increases expression of type I interferon stimulated genes in response to LPS. By contrast, increased LUCAT1 expression results in a reduction of the inducible ISG response. In activated cells, LUCAT1 is enriched in the nucleus where it associates with chromatin. Further, LUCAT1 limits transcription of interferon stimulated genes by interacting with STAT1 in the nucleus. Together, our study highlights the role of the lncRNA LUCAT1 as a post-induction feedback regulator which functions to restrain the immune response in human cells.

Abstract IA12: Dynamic metabolic regulation of epigenetic remodeling in macrophages

Abstract Over the course of an immune response, macrophages undergo a sequence of functional transitions. These transitions are coupled to dynamic rewiring of cellular metabolism. The impact of metabolic state on chromatin modifications allows the dynamic metabolic reprogramming to orchestrate immunity during immune responses. Specifically, we found that in response to the classic stimuli lipopolysaccharide and interferon-γ, pyruvate dehydrogenase complex is profoundly inhibited over time, mediating the metabolic transition from the early pro-inflammatory stage to the later more immunosuppressive stage. The regulation of PDHC activity dynamically controls cellular acetyl-coA availability. We will discuss how this affects histone acetylation in macrophages over a course of prolonged stimulation and upon repeated stimulation. Furthermore, our study revealed that several metabolites directly involved in the addition or removal of histone methylation, such as S-adenosyl-methionine and succinate, show highly dynamic changes during the immune response. We will discuss which specific epigenetic modifications are sensitive to fluctuations in metabolite levels. This work reveals important mechanisms connecting metabolism, epigenetic and changes in macrophage functions during immune response. Citation Format: Jing Fan. Dynamic metabolic regulation of epigenetic remodeling in macrophages [abstract]. In: Abstracts: AACR Special Virtual Conference on Epigenetics and Metabolism; October 15-16, 2020; 2020 Oct 15-16. Philadelphia (PA): AACR; Cancer Res 2020;80(23 Suppl):Abstract nr IA12.

Pro-inflammatory response ensured by LPS and Pam3CSK4 in RAW 264.7 cells did not improve a fungistatic effect on Cryptococcus gattii infection.

BackgroundThe macrophage lineage is characterized by plasticity due to the acquisition of distinct functional phenotypes, and two major subsets are evaluated; classical M1 activation (strong microbicidal activity) and alternative M2 activation (immunoregulatory functions). The M1 subset expresses inducible nitric oxide synthase (iNOS), which is a primary marker to identify these cells, whereas M2 macrophages are characterized by expression of Arginase-1, found in inflammatory zone 1 (Fizz1), chitinase-like molecule (Ym-1), and CD206. The micro-environmental stimuli and signals in tissues are critical in the macrophage polarization. Toll-like receptors (TLR) ligands, such as lipopolysaccharide (LPS), palmitoyl-3-cysteine-serine-lysine-4 (Pam3CSK4), and ArtinM (mannose-binding lectin) are inductors of M1 subset. The impact of TLR2 and TLR4 signals to fight against Cryptococcus gattii infection is unknown, which is a fungal pathogen that preferentially infects the lung of immunocompetent individuals. The macrophages initiate an immune response to combat the C. gattii, then we evaluated in RAW 264.7 cell the effect of TLR2 and TLR4 agonists on the macrophage polarization dynamic and the impact on the growth of C. gattii.Methods and ResultsWe demonstrated that P3C4, LPS, and ArtinM induced an increase in the levels of iNOS transcripts in RAW 264.7 cells, whereas the relative expression of arginase-1, Ym-1, and Fizz1 was significantly increased in the presence of IL-4 alone. The effects of TLR2 and TLR4 agonists on repolarization from the M2 to M1 subset was evaluated, and the first stimulus was composed of IL-4 and, after 24 h of incubation, the cells were submitted to a second stimulus of P3C4, LPS, ArtinM, or Medium. These TLR agonists induced the production of TNF-α in polarized RAW 264.7 cells to the M2 subset, moreover the measurement of M1/M2 markers using qRT-PCR demonstrated that a second stimulus with LPS for 24 h induced a significant augmentation of levels of iNOS mRNA. This impact of TLR2 and TLR4 agonists in the activation of the RAW 264.7 macrophage was assayed in the presence of C. gattii, the macrophages stimulated with TLR2 and TLR4 agonists for 24 h and co-cultured with C. gattii, as a second stimulus, reached high levels of TNF-α even after incubation with different concentrations of C. gattii. The activation of RAW 264.7 cells induced by TLR2 and TLR4 agonists favored the phagocytosis of C. gattii and inhibited the growth of yeast in the early period of infection. However, RAW 264.7 cells incubated with C. gattii in the presence of TLR2 and TLR4 agonists did not result a significant difference in the colony forming unit (CFU) assay in the early period of C. gattii infection, compared to negative control.ConclusionPolarized RAW 264.7 cells to the M1 subset with TLR2 and TLR4 agonists did not inhibit the growth of C. gattii, whereas robust immunity was identified that could dysregulate host tolerance to this pathogen.

Inhibition of yes-associated protein dephosphorylation prevents aggravated periodontitis with occlusal trauma.

Occlusal trauma can aggravate periodontitis, but the mechanism remains unclear. Yes-associated protein (YAP), a mechanical stressor protein, may play an important role in this process. Western blot and quantitative real-time polymerase chain reaction (qRT-PCR) were applied to detect the expression of YAP and inflammatory factors in patients with periodontitis accompanied with or without occlusal trauma. Through local administration of Porphyromonas gingivalis and composite resin bonding on maxillary molars in mice, we established periodontitis and occlusal trauma models. Treatment with or without XAV939, to inhibit YAP activation, was performed in these models. Micro-computed tomography, immunofluorescence (IF), and qRT-PCR were used to explore the YAP pathway in periodontitis with occlusal trauma. Cyclic stress and lipopolysaccharide (LPS) stimuli were applied to the L929 mouse fibroblast cell line with or without XAV939. Western blot, IF, and qRT-PCR were used to verify the in vivo results. Activated dephosphorylated YAP and increased expression of inflammatory factors were observed in patients with periodontitis accompanied with occlusal trauma. In the mouse model of periodontitis with occlusal trauma, YAP transferred into the nucleus, resulting in Jun N-terminal kinases (JNK) related pro-inflammatory pathway up-regulation. L929 cell cyclic stress and LPS stimulation results confirmed the in vivo results. Application of XAV939 inhibited YAP protein dephosphorylation and reduced JNK pro-inflammatory pathway factor expression in vivo and in vitro. Occlusal trauma can activate YAP nuclear transfer, resulting in the up-regulation of the JNK pro-inflammatory pathway. This can be inhibited by the XAV939 YAP inhibitor.

β-hydroxybutyrate (β-HB) exerts anti-inflammatory and antioxidant effects in lipopolysaccharide (LPS)-stimulated macrophages in Liza haematocheila

Poly-β-hydroxybutyrate (PHB) can be hydrolyzed to β-hydroxybutyrate (β-HB) in the intestinal tract of animals, and dietary PHB supplementation could enhance the immunity and disease resistance of aquatic animals. Antioxidant system is responsive to PHB stimuli via MAPK/PI3K-Akt/TNF/NF-κB/TCR/TLR signaling pathways. However, the precise immunopotentiation mechanism needs further study. In this study, macrophages from spleen in Liza haematocheila was used to study the effect of β-HB on cell viability and antioxidant function to illustrate the immunopotentiation mechanism of PHB. The results showed that β-HB (100 μg/mL) promoted the viability of macrophages and balanced the production of reactive oxygen species, but inhibited the excessive production of intracellular nitric oxide. In order to further explore the immunopotentiation mechanism of β-HB, LPS (100 μg/mL) was used to induce the inflammation and investigated the inhibitory effect of β-HB on inflammation. The results showed that LPS could induce inflammation successfully, and β-HB exerted anti-inflammatory and antioxidant effects in LPS-stimulated macrophages. Compared with LPS stimuli alone, the expression of anti-inflammatory genes NF-κBIA, MAP3K8 and TLR5 in β-HB pretreatment group was up-regulated, and the expression of pro-inflammatory genes TNFSF6, TNF-α, PI3K, NF-κB and TLR1 down-regulated. It suggested that β-HB inhibited the inflammatory response by up-regulation of anti-inflammatory genes such as NF-κBIA, thereby enhancing the immunity of the body.

Nanostructured Lipid Carriers Made of Ω-3 Polyunsaturated Fatty Acids: In Vitro Evaluation of Emerging Nanocarriers to Treat Neurodegenerative Diseases.

Neurodegenerative diseases (ND) are one of the main problems of public health systems in the 21st century. The rise of nanotechnology-based drug delivery systems (DDS) has become in an emerging approach to target and treat these disorders related to the central nervous system (CNS). Among others, the use of nanostructured lipid carriers (NLCs) has increased in the last few years. Up to today, most of the developed NLCs have been made of a mixture of solid and liquid lipids without any active role in preventing or treating diseases. In this study, we successfully developed NLCs made of a functional lipid, such as the hydroxylated derivate of docohexaenoic acid (DHAH), named DHAH-NLCs. The newly developed nanocarriers were around 100 nm in size, with a polydispersity index (PDI) value of <0.3, and they exhibited positive zeta potential due to the successful chitosan (CS) and TAT coating. DHAH-NLCs were shown to be safe in both dopaminergic and microglia primary cell cultures. Moreover, they exhibited neuroprotective effects in dopaminergic neuron cell cultures after exposition to 6-hydroxydopamine hydrochloride (6-OHDA) neurotoxin and decreased the proinflammatory cytokine levels in microglia primary cell cultures after lipopolysaccharide (LPS) stimuli. The levels of the three tested cytokines, IL-6, IL-1β and TNF-α were decreased almost to control levels after the treatment with DHAH-NLCs. Taken together, these data suggest the suitability of DHAH-NLCs to attaining enhanced and synergistic effects for the treatment of NDs.

DGLA from the Microalga Lobosphaera Incsa P127 Modulates Inflammatory Response, Inhibits iNOS Expression and Alleviates NO Secretion in RAW264.7 Murine Macrophages.

Microalgae have been considered as a renewable source of nutritional, cosmetic and pharmaceutical compounds. The ability to produce health-beneficial long-chain polyunsaturated fatty acids (LC-PUFA) is of high interest. LC-PUFA and their metabolic lipid mediators, modulate key inflammatory pathways in numerous models. In particular, the metabolism of arachidonic acid under inflammatory challenge influences the immune reactivity of macrophages. However, less is known about another omega-6 LC-PUFA, dihomo-γ-linolenic acid (DGLA), which exhibits potent anti-inflammatory activities, which contrast with its delta-5 desaturase product, arachidonic acid (ARA). In this work, we examined whether administrating DGLA would modulate the inflammatory response in the RAW264.7 murine macrophage cell line. DGLA was applied for 24 h in the forms of carboxylic (free) acid, ethyl ester, and ethyl esters obtained from the DGLA-accumulating delta-5 desaturase mutant strain P127 of the green microalga Lobosphaera incisa. DGLA induced a dose-dependent increase in the RAW264.7 cells’ basal secretion of the prostaglandin PGE1. Upon bacterial lipopolysaccharide (LPS) stimuli, the enhanced production of pro-inflammatory cytokines, tumor necrosis factor alpha (TNFα) and interleukin 1β (IL-1β), was affected little by DGLA, while interleukin 6 (IL-6), nitric oxide, and total reactive oxygen species (ROS) decreased significantly. DGLA administered at 100 µM in all forms attenuated the LPS-induced expression of the key inflammatory genes in a concerted manner, in particular iNOS, IL-6, and LxR, in the form of free acid. PGE1 was the major prostaglandin detected in DGLA-supplemented culture supernatants, whose production prevailed over ARA-derived PGE2 and PGD2, which were less affected by LPS-stimulation compared with the vehicle control. An overall pattern of change indicated DGLA’s induced alleviation of the inflammatory state. Finally, our results indicate that microalgae-derived, DGLA-enriched ethyl esters (30%) exhibited similar activities to DGLA ethyl esters, strengthening the potential of this microalga as a potent source of this rare anti-inflammatory fatty acid.

Antagonistic effect of N-acetyl-L-cysteine against cadmium-induced cytotoxicity and abnormal immune response on chicken peritoneal macrophages

Cadmium is a highly toxic metal threatening human and animal health. N-acetyl-L-cysteine (NAC) was reported to play a positive role in disease treatment and immune regulation. The present study aimed to explore the effect of NAC administration on Cd-induced cytotoxicity and abnormal immune response on chicken peritoneal macrophages. Peritoneal macrophages isolated from Isa Brown male chickens were exposed to CdCl2 (20 or 50 μM) and/or NAC (500 μM) for different time periods. Results showed that Cd caused dose-dependent damage on chicken peritoneal macrophages characterized by morphologic and ultrastructural alterations, increased cell apoptosis, reactive oxygen species accumulation and mitochondrial injury. Cd exposure inhibited phagocytic activity of chicken peritoneal macrophages, and promoted transcriptional status of pro-inflammatory cytokines (IL-1β, IL-6 and TNF-α) in both unactivated macrophages and cells in response to lipopolysaccharide (LPS) stimuli. Pretreatment with 500 μM NAC did not affect growth of normal chicken peritoneal macrophages, while remarkably inhibiting Cd-caused cell death, oxidative stress, and mitochondrial membrane depolarization. NAC pretreatment significantly prevented intracellular Cd2+ accumulation in the Cd-exposed macrophages. Inhibitory effects of NAC on Cd-induced ROS accumulation and mitochondrial injury on chicken macrophages were confirmed in HD-11 macrophage cell line. In addition, NAC pretreatment promoted the phagocytic activity of Cd-exposed chicken peritoneal macrophages, and significantly inhibited expression of pro-inflammatory factors (IL-1β, IL-6 and TNF-α) in both Cd-exposed macrophages and Cd-treated cells in response to LPS stimuli. In conclusion, the present study firstly demonstrated the antagonistic effect of NAC against Cd-caused damage and abnormal immune response on chicken peritoneal macrophages. Protective effect of NAC on chicken macrophages was highly related to its suppression on Cd-induced ROS overproduction, pro-inflammatory reaction and intracellular Cd2+ accumulation.

Allomyrina dichotoma larval extract attenuates intestinal barrier disruption by altering inflammatory response and tight junction proteins in lipopolysaccharide-induced Caco-2 cells

Intestinal epithelial cells form a barrier between the intestinal lumen and host connective tissues and play an important role in maintaining intestinal nutrient homeostasis. This study investigated effects of Allomyrina dichotoma (rhinoceros beetle) larval extract (ADLE) on the intestinal barrier damage and explored mechanisms for reversing intestinal barrier dysfunction in lipopolysaccharide (LPS)-stimulated Caco-2, human intestinal epithelial cells. LPS reduced intestinal epithelial barrier function by increasing transepithelial electrical resistance, and this effect was significantly attenuated by ADLE treatment. ADLE also significantly countered the inhibition of tight junction-related protein expression in both LPS-induced Caco-2 cells and intestine from HFD-induced mice. Moreover, ADLE significantly decreased expression and production of inflammatory factors, such as iNOS, cox-2, nitric oxide, and cytokines induced by LPS stimulus. Reduction in phosphorylation of adenosine monophosphate-activated protein kinase was averted by ADLE treatment in LPS treated INS-1 cells. Finally, reactive oxygen stress level was decreased and ATP production was increased by ADLE treatment. ADLE appears to display gut health-promoting effects by reducing inflammation and inducing tight junction proteins in Caco-2 cells. Therefore, ADLE might be useful for preventing or treating intestine cell damage in inflammatory bowel disease.

An association between mitochondria and microglia effector function. What do we think we know?

While resident innate immune cells of the central nervous system, the microglia, represent a cell population unique in origin, microenvironment, and longevity, they assume many properties displayed by peripheral macrophages. One prominent shared property is the ability to undergo a metabolic switch towards glycolysis and away from oxidative phosphorylation (OXPHOS) upon activation by the pro-inflammatory stimuli lipopolysaccharide. This shift serves to meet specific cellular demands and allows for cell survival, similar to the Warburg effect demonstrated in cancer cells. In contrast, normal survelliance phenotype or stimulation to a non-proinflammatory phenotype relies primarily on OXPHOS and fatty acid oxidation. Thus, mitochondria appear to function as a pivotal signaling platform linking energy metabolism and macrophage polarization upon activation. These unique shifts in cell bioenergetics in response to different stimuli are essential for proper effector responses at sites of infection, inflammation, or injury. Here we present a summary of recent developments as to how these dynamics characterized in peripheral macrophages are displayed in microglia. The new insights provided by an increased understanding of metabolic reprogramming in macrophages may allow for translation to the CNS and a better understanding of microglia heterogeneity, regulation, and function.

Immuno-modulatory effects of macluraxanthone on macrophage phenotype and function

Macluraxanthone was previously reported to have many biological activities, including anti-cholinesterase, anti-oxidant, anti-cancer, anti-malarial and anti-inflammatory effects. The aim of the current study was to further characterise the effect of macluraxanthone on human macrophage, a type of immune cell that has been implicated in the development of various inflammatory diseases. The expression of surface markers and cytokine production by THP-1 human macrophages following treatment with macluraxanthone were investigated. Macluraxanthone was shown to promote polarisation of M1-like pro-inflammatory macrophages by increasing the percentage of macrophages expressing CD86, while decreasing their CD14, CD11b and CD80 expression. However, in the presence of the pro-inflammatory stimulus lipopolysaccharide, macluraxanthone significantly decreased TNF-α and IL-10 cytokine production.

A unique hybrid characteristic having both pro- and anti-inflammatory phenotype transformed by repetitive low-dose lipopolysaccharide in C8-B4 microglia

Although lipopolysaccharide (LPS) is regarded as an inducer of inflammation, previous studies have suggested that repetitive low-dose LPS has neuroprotective effects via immunomodulation of microglia, resident macrophages of brain. However, microglia transformed by the stimulus of repetitive low-dose LPS (REPELL-microglia) are not well characterized, whereas microglia transformed by repetitive high-dose LPS are well studied as an endotoxin tolerance model in which the induction of pro-inflammatory molecules is suppressed. In this study, to characterize REPELL-microglia, the gene expression and phagocytic activity of REPELL-microglia were analyzed with the murine C8-B4 microglia cell line. The REPELL-microglia were characterized by a high expression of pro-inflammatory molecules (Nos2, Ccl1, IL-12B, and CD86), anti-inflammatory molecules (IL-10, Arg1, Il13ra2, and Mrc1), and neuroprotective molecules (Ntf5, Ccl7, and Gipr). In addition, the phagocytic activity of REPELL-microglia was promoted as high as that of microglia transformed by single low-dose LPS. These results suggest the potential of REPELL-microglia for inflammatory regulation, neuroprotection, and phagocytic clearance. Moreover, this study revealed that gene expression of REPELL-microglia was distinct from that of microglia transformed by repetitive high-dose LPS treatment, suggesting the diversity of microglia transformation by different doses of LPS.