Protective effects of leucine against lipopolysaccharide-induced inflammatory response in Labeo rohita fingerlings

Progressive Skeletal Muscle Atrophy in Muscular Dystrophies: A Role for Toll-like Receptor-Signaling in Disease Pathogenesis

Muscle atrophy is an active process controlled by specific transcriptional programs, in which muscle mass is lost by increased protein degradation and/or decreased protein synthesis. This review explores the involvement of Toll-like receptors (TLRs) in the muscle atrophy as it is observed in muscular dystrophies, disorders characterized by successive bouts of muscle fiber degeneration and regeneration in an attempt to repair contraction-induced damage. TLRs are defense receptors that detect infection and recognize self-molecules released from damaged cells. In muscular dystrophies, these receptors become over-active, and are firmly involved in the sustained chronic inflammation exhibited by the muscle tissue, via their induction of pro-inflammatory cytokine expression. Taming the exaggerated activation of TLR2/4 and TLR7/8/9, and their downstream effectors in particular, comes forward as a therapeutic strategy with potential to slow down disease progression.

Florfenicol alleviated lipopolysaccharide (LPS)-induced inflammatory responses in Ctenopharyngodon idella through inhibiting toll / NF-κB signaling pathways

The present study was conducted to evaluate the anti-inflammatory activity of florfenicol (FFC) against lipopolysaccharide (LPS)-induced inflammatory responses in Ctenopharyngodon idella in vivo and in vitro. Head-kidney (HK) macrophages were pre-treated with 10 μg/mL LPS and then exposed to different concentrations of FFC to determine its in vitro anti-inflammatory activity. Inhibitory effect of FFC on inflammatory mediators TNF-α, IL-6 and IL-1β, as well as LPS-induced nitric oxide (NO) and prostaglandin E 2 (PGE 2) production were assayed by ELISA. The expression level of nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) were investigated by RT-PCR. Expression level of TLR-related genes (TLR1, TLR2, TLR4, TLR7, TLR8) expression, tumor necrosis factor receptor-associated factor 6 (TRAF6), transforming growth factor-b-activated kinase 1 (TAK1), Myeloid differentiation factor 88 (MyD88), nucleus p65, NF-κBα (IκBα) were measured by RT-PCR after grass carp were treated with 50, 100 and 200 mg FFC/kg body weight for 3 days. Results from in vitro tests demonstrated that FFC dose-dependently inhibited LPS-induced inflammatory cytokines TNF-α, IL-6 and IL-1β, inflammatory factors NO and PGE 2 production in macrophages. In addition, iNOS and COX-2 expression levels decreased significantly as compared with LPS treated group. In vivo test demonstrated that treatment with FFC prevented the LPS-induced upregulation of TNF-α, IL-6, IL-1β, NO and PGE 2. The expression level of iNOS, and COX-2 in FFC-treated grass carp were also downregulated as compared with LPS treated fish. Besides, FFC blocked the expression of Toll-like receptor 2 (TLR2) and then suppressed the phosphorylation of nuclear transcription factor-kappa B (NF-κB) p65 and degradation inhibitor of IκBα. Furthermore, administration of FFC inhibited the up-regulation of IRAK4, TRAF6 and TAK1 induced by LPS. These results suggest that the anti-inflammatory properties of FFC might be the results from the inhibition of iNOS, COX-2, IL-6, IL-1β, and TNF-α expressions through the down-regulation of Toll/NF-κB signaling pathways.

Leucine competes with kynurenine for blood-to-brain transport and prevents lipopolysaccharide-induced depression-like behavior in mice

Inflammation activates indoleamine 2,3-dioxygenase (IDO) which metabolizes tryptophan into kynurenine. Circulating kynurenine is transported into the brain by the large amino transporter LAT1 at the level of the blood-brain barrier. We hypothesized that administration of leucine that has a high affinity for LAT1 should prevent the entry of kynurenine into the brain and attenuate the formation of neurotoxic kynurenine metabolites. To test whether leucine could prevent inflammation-induced depression-like behavior, mice were treated with lipopolysaccharide (LPS, 0.83 mg/kg IP) or saline and treated with L-leucine (50 mg/kg, IP) or vehicle administered before and 6 h after LPS. Depression-like behavior was measured by increased duration of immobility in the forced swim test and decreased sucrose preference. Leucine decreased brain kynurenine levels, blocked LPS-induced depression-like behavior and had antidepressant-like effects in control mice. Leucine had no effect of its own on sickness behavior and neuroinflammation. To confirm that leucine acts by interfering with the transport of kynurenine into the brain, mice were injected with L-leucine (300 mg/kg, IP) immediately before kynurenine (33 mg/kg IP) and brain kynurenine and depression-like behavior were measured 3 h later. Leucine did prevent the entry of exogenous kynurenine into the brain and abrogated depression-like behavior measured by increased duration of immobility in the forced swim test. Additional experiments using an in vitro model of the blood-brain barrier confirmed that kynurenine competes with leucine at the level of the amino acid transporter LAT1 for brain uptake. These experiments also revealed that efflux was the dominant direction of kynurenine transport and was largely independent of LAT1 and leucine, which explains why leucine could block brain uptake of kynurenine without affecting brain clearance. These findings demonstrate that leucine has antidepressant properties vis-à-vis inflammation-induced depression and one mechanism for this is by blocking the ability of kynurenine to enter the brain.

Astaxanthin protects lipopolysaccharide-induced inflammatory response in Channa argus through inhibiting NF-κB and MAPKs signaling pathways

The present study was conducted to evaluate the protective effects of astaxanthin against lipopolysaccharide (LPS)-induced inflammatory responses in Channa argus in vivo and ex vivo. Primary hepatocytes were exposed to different concentrations of LPS for 24 h to induce an inflammatory response, and the protective effects of astaxanthin against LPS-induced inflammation were studied ex vivo and in vivo. Hepatocytes exposed to LPS (5-20 μg mL^-1) alone for 24 h resulted in a significant increase in lactate dehydrogenase release (LDH), Nitric oxide (NO) production and Malondialdehyde (MDA) content, 10 μg mL^-1 LPS could induced inflammatory response in hepatocytes. Gene expression of TLR4, NFkBp65, MAPKp38, TNF-α, IL-6 and IL-1β mRNA expression were also enhanced ex vivo (p < 0.05). In vivo test demonstrated that pretreatment with astaxanthin prevented the LPS-induced upregulation of pro-inflammatory cytokines TNF-α, IL-6 and IL-1β. Besides, astaxanthin blocked the expression of Toll-like receptor 4 (TLR4) and then suppressed the phosphorylation of nuclear transcription factor-kappa B (NF-κB) p65 and degradation inhibitor of NF-κBα (IκBα). Further study showed that astaxanthin could suppress the phosphorylation of p38, extracellular signal-regulated kinase (ERK) and c-jun NH2-terminal kinase (JNK) in mitogen-activated protein kinase (MAPK) signal pathway. In conclusion, our results suggest that astaxanthin played an anti-inflammatory role by regulating TLR4 and the NF-κB and MAPK signaling pathways in C. argus.