Background: Huntington’s disease (HD) is caused by the expression of a mutated variant of Huntingtin (mHtt), which results in the complex pathology characterized by a defective function of the nervous system and altered inflammatory responses. While the neuronal effects of mHtt expression have been extensively studied, its effects on the physiology of immune cells have not been fully described. Mast cells (MCs) are unique tissue-resident immune cells whose activation has been linked to protective responses against parasites and bacteria, but also to deleterious inflammatory allergic reactions and, recently, to neurodegenerative diseases.Methods: Bone marrow-derived mast cells (BMMCs) were obtained from wild-type (WT-) and mHtt-expressing (R6/1) mice to evaluate the main activation parameters triggered by the high-affinity IgE receptor (FcεRI) and the Toll-like receptor (TLR) 4. Degranulation was assessed by measuring the secretion of β-hexosaminidase, MAP kinase activation was detected by Western blot, and cytokine production was determined by RT-PCR and ELISA. TLR-4 receptor and Htt vesicular trafficking was analyzed by confocal microscopy. In vivo, MC-deficient mice (c-Kit^Wsh/Wsh) were intraperitonally reconstituted with WT or R6/1 BMMCs and the TLR4-induced production of the tumor necrosis factor (TNF) was determined by ELISA. A survival curve of mice treated with a sub-lethal dose of bacterial lipopolysaccharide (LPS) was constructed.Results: R6/1 BMMCs showed normal β-hexosaminidase release levels in response to FcεRI, but lower cytokine production upon LPS stimulus. Impaired TLR4-induced TNF production was associated to the lack of intracellular dynamin-dependent TLR-4 receptor trafficking to perinuclear regions in BMMCs, a diminished ERK1/2 and ELK-1 phosphorylation, and a decrease inc-fosand TNF mRNA accumulation. R6/1 BMMCs also failed to produce TLR4-induced anti-inflammatory cytokines (like IL-10 and TGF-β). The detected defects were also observed in vivo, in a MCs-dependent model of endotoxemia. R6/1 andc-Kit^Wsh/Wshmice reconstituted with R6/1 BMMCs showed a decreased TLR4-induced TNF production and lower survival rates to LPS challenge than WT mice.Conclusions: Our data show that mHtt expression causes an impaired production of pro- and anti-inflammatory mediators triggered by TLR-4 receptor in MCs in vitro and in vivo, which could contribute to the aberrant immunophenotype observed in HD.

Objective: To determine the role of anion exchanger 3 (AE3) in dorsal root ganglion (DRG) in nerve injury-induced chronic nociception in the rat. Methods: Spared nerve injury (SNI) was used to induce neuropathic pain. Von Frey filaments and Hargreaves test were used to assess tactile allodynia and thermal hyperalgesia, respectively. Drugs were given by intrathecal administration. Western blotting was used to determine AE3 expression in DRG. Key findings: SNI produced long-lasting mechanical allodynia and thermal hyperalgesia. AE3 was found in DRG of sham-operated rats. SNI enhanced baseline AE3 expression in L4 and L5 DRGs at days 7 and 14, respectively. In contrast, SNI did not affect AE3 expression in L6 DRG. AE3 expression returned to baseline levels 21 days after SNI. Intrathecal 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid (DIDS) (5–50 μg) pretreatment prevented SNI-induced allodynia and, at a lesser extent, hyperalgesia. Moreover, DIDS (50 μg) reduced SNI-induced AE3 upregulation in L4, but not L5, DRGs. Intrathecal DIDS (5–50 μg) or anti-AE3 antibody (1 μg), but not vehicle, post-treatment (6 days) partially reversed SNI-induced allodynia and hyperalgesia. DIDS or anti-AE3 antibody post-treatment diminished SNI-induced AE3 upregulation in L4 and L5 DRGs. Conclusions: Data suggest that AE3 is present in DRG and contributes to mechanical allodynia and thermal hyperalgesia in neuropathic rats.

Jacareubin (2), nujiangexanthone A, and α-mangostin display the highest anti-allergic effects among the active xantones through still not well-known mechanisms. This study investigates the SAR of jacareubin, its precursor xanthone V (1) and their peracetylated (1a and 2a), permethylated (1b and 2b) derivatives and their anti-allergic and anti-inflammatory effects. To characterize the inhibitory effect of jacareubin, 2a and 2b on the anaphylactic reaction, we first utilized in vitro models of bone marrow derived mast cells (BMMCs), determining their capacity of inhibiting the IgE/Antigen-induced degranulation, myeloperoxidase (MPO), and xanthine oxidase (XO) activation. Also, we utilized in vivo models of passive cutaneous anaphylaxis (PCA) and TPA-induced ear edema. In vitro tests showed that the compound 2b was more effective than jacareubin in the inhibition of BMMCs degranulation. Besides, in vivo models of PCA revealed that the fourth cyclized ring of jacareubin is the critical structural element for anti-allergic efficacy, as compound 1 was less effective. Additionally, hydroxyl groups were found to be essential for inhibiting MPO. Jacareubin was the only tested xanthone that directly inhibited XO, a result supported by molecular docking. Overall, jacareubin represents a promising multi-target scaffold that could be used for developing new treatments for inflammatory and allergic diseases.