BackgroundOxaliplatin, a platinum-based chemotherapeutic agent, causes an unusual acute peripheral neuropathy. Oxaliplatin-induced acute peripheral neuropathy appears in almost all patients rapidly after infusion, and is triggered or exacerbated by cold, while its mechanisms are poorly understood. In this study, the involvement of thermosensitive transient receptor potential channels (TRPA1, TRPM8 and TRPV1) in oxaliplatin-induced acute hypersensitivity was investigated in mice.ResultsA single intraperitoneal administration of oxaliplatin (1–10 mg/kg) induced cold but not mechanical hypersensitivity within 2 h in a dose-dependent manner. Infusion of the oxaliplatin metabolite, oxalate (1.7 mg/kg), also induced acute cold hypersensitivity, while another platinum-based chemotherapeutic agent, cisplatin (5 mg/kg), or the non-platinum-containing chemotherapeutic agent, paclitaxel (6 mg/kg) failed to induce mechanical or cold hypersensitivity. The oxaliplatin-induced acute cold hypersensitivity was abolished by the TRPA1 antagonist HC-030031 (100 mg/kg) and by TRPA1 deficiency. The nocifensive behaviors evoked by intraplantar injections of allyl-isothiocyanate (AITC; TRPA1 agonist) were significantly enhanced in mice treated for 2 h with oxaliplatin (1–10 mg/kg) in a dose-dependent manner, while capsaicin (TRPV1 agonist)-evoked nocifensive behaviors were not affected. Menthol (TRPM8/TRPA1 agonist)-evoked nocifensive-like behaviors were also enhanced by oxaliplatin pretreatment, which were inhibited by TRPA1 deficiency. Similarly, oxalate enhanced, but neither cisplatin nor paclitaxel affected AITC-evoked nocifensive behaviors. Pretreatment of cultured mouse dorsal root ganglia (DRG) neurons with oxaliplatin (30–300 μM) for 1, 2, or 4 h significantly increased the number of AITC-sensitive neurons in a concentration-dependent manner whereas there was no change in the number of menthol- or capsaicin-sensitive neurons.ConclusionsTaken together, these results suggest that a brief treatment with oxaliplatin or its metabolite oxalate is sufficient to enhance the responsiveness of TRPA1 but not that of TRPM8 and TRPV1 expressed by DRG neurons, which may contribute to the characteristic acute peripheral neuropathy induced by oxaliplatin.

We have previously shown that endochondral ossification is finely regulated by the Clock system expressed in chondrocytes during postnatal skeletogenesis. Here we show a sophisticated modulation of bone resorption and bone mass by the Clock system through its expression in bone-forming osteoblasts. Brain and muscle aryl hydrocarbon receptor nuclear translocator-like protein 1 (Bmal1) and Period1 (Per1) were expressed with oscillatory rhythmicity in the bone in vivo, and circadian rhythm was also observed in cultured osteoblasts of Per1::luciferase transgenic mice. Global deletion of murine Bmal1, a core component of the Clock system, led to a low bone mass, associated with increased bone resorption. This phenotype was recapitulated by the deletion of Bmal1 in osteoblasts alone. Co-culture experiments revealed that Bmal1-deficient osteoblasts have a higher ability to support osteoclastogenesis. Moreover, 1α,25-dihydroxyvitamin D [1,25(OH) D ]-induced receptor activator of nuclear factor κB ligand (Rankl) expression was more strongly enhanced in both Bmal1-deficient bone and cultured osteoblasts, whereas overexpression of Bmal1/Clock conversely inhibited it in osteoblasts. These results suggest that bone resorption and bone mass are regulated at a sophisticated level by osteoblastic Clock system through a mechanism relevant to the modulation of 1,25(OH) D -induced Rankl expression in osteoblasts. © 2017 American Society for Bone and Mineral Research.

Mammalian transient receptor potential ankyrin 1 (TRPA1) is a polymodal nociceptor that plays an important role in pain generation, but its role as a cold nociceptor is still controversial. Here, we propose that TRPA1 can sense noxious cold via transduction of reactive oxygen species (ROS) signalling. We show that inhibiting hydroxylation of a proline residue within the N-terminal ankyrin repeat of human TRPA1 by mutation or using a prolyl hydroxylase (PHD) inhibitor potentiates the cold sensitivity of TRPA1 in the presence of hydrogen peroxide. Inhibiting PHD in mice triggers mouse TRPA1 sensitization sufficiently to sense cold-evoked ROS, which causes cold hypersensitivity. Furthermore, this phenomenon underlies the acute cold hypersensitivity induced by the chemotherapeutic agent oxaliplatin or its metabolite oxalate. Thus, our findings provide evidence that blocking prolyl hydroxylation reveals TRPA1 sensitization to ROS, which enables TRPA1 to convert ROS signalling into cold sensitivity.

Similar to neurons, microglia have an intrinsic molecular clock. The master clock oscillator Bmal1 modulates interleukin-6 upregulation in microglial cells exposed to lipopolysaccharide. Bmal1 can play a role in microglial inflammatory responses. We previously demonstrated that gliotransmitter ATP induces transient expression of the clock gene Period1 via P2X7 purinergic receptors in cultured microglia. In this study, we further investigated mechanisms underlying the regulation of pro-inflammatory cytokine production by clock molecules in microglial cells. Several clock gene transcripts exhibited oscillatory diurnal rhythmicity in microglial BV-2 cells. Real-time luciferase monitoring also showed diurnal oscillatory luciferase activity in cultured microglia from Per1::Luciferase transgenic mice. Lipopolysaccharide (LPS) strongly induced the expression of pro-inflammatory cytokines in BV-2 cells, whereas an siRNA targeting Brain and muscle aryl hydrocarbon receptor nuclear translocator-like protein 1 (Bmal1), a core positive component of the microglial molecular clock, selectively inhibited LPS-induced interleukin-6 (IL-6) expression. In addition, LPS-induced IL-6 expression was attenuated in microglia from Bmal1-deficient mice. This phenotype was recapitulated by pharmacological disruption of oscillatory diurnal rhythmicity using the synthetic Rev-Erb agonist SR9011. Promoter analysis of the Il6 gene revealed that Bmal1 is required for LPS-induced IL-6 expression in microglia. Mice conditionally Bmal1 deficient in cells expressing CD11b, including microglia, exhibited less potent upregulation of Il6 expression following middle cerebral artery occlusion compared with that in control mice, with a significant attenuation of neuronal damage. These results suggest that the intrinsic microglial clock modulates the inflammatory response, including the positive regulation of IL-6 expression in a particular pathological situation in the brain, GLIA 2016. GLIA 2017;65:198-208.

Functional food ingredients, including prebiotics, have been ardently developed for improving the intestinal environment. Fructooligosaccarides (FOS), including fructans, are the well researched and commercialized prebiotics. However, to our knowledge, few studies have been conducted on the physiological effects of each component of FOS as prebiotics. 1-Kestose, a component of FOS, is composed of one glucose and two fructose molecules, and is considered as a key prebiotic component in short-chain FOS. In the present study, we examined the effects of dietary 1-kestose using 0.5–5% 1-kestose diets on cecal microbiota composition and cecal contents of short-chain fatty acids and lactate in rats. The findings indicate that dietary 1-kestose induced cecal hypertrophy and alterations in the cecal microbiota composition, including a marked increase in the cell number of Bifidobacterium spp. These alterations were associated with significant increases in acetate and lactate, and a marked increase in butyrate in cecal contents. Furthermore, dietary 1-kestose induced a significant decrease in serum insulin concentration in rats fed 2.5–5% 1-kestose diet. These findings suggest a potential of 1-kestose to be a prebiotic for improving the metabolism of the host.