Chicago Sky Blue 6B

Chicago Sky Blue 6B is a counterstain for background autofluorescence in fluorescence and immunofluorescence histochemistry^[1]. Chicago Sky Blue 6B is a potent competitive inhibitor of vesicular glutamate transporter 1 (VGLUT1) with an IC₅₀ of 3μM^[2]. Chicago Sky Blue 6B is the first small molecule PrP ligand that can inhibit Aβ binding^[3]. Chicago Sky Blue 6B has anti-inflammatory activity^[4].

In vitro, Chicago Sky Blue 6B (3.3-10μM) treatment of Aβ- and lipopolysaccharide-treated BV2 microglia for 1h significantly inhibited the production of proinflammatory cytokines such as Tumor necrosis factor-α (TNF-α) and Interleukin-1β (IL-1β)^[5]. Treatment of primary mouse bone marrow monocytes/macrophages (BMMs) with Chicago Sky Blue 6B (5, 10, 20μM) for 5-7 days inhibited osteoclast differentiation and bone resorption function and suppressed early NF-κB signaling^[6].

In vivo, treatment of A53T α-synuclein transgenic (Tg) mice with Chicago Sky Blue 6B (20mg/kg/day) for 3 months rescued the motor coordination defects of Tg mice and significantly reduced the levels of S129-phosphorylated α-synuclein (pS129) in the brain regions and glial acidic protein (GFAP) immunoreactivity in the prefrontal cortex of Tg mice^[7].

References:
[1] Priya S, Kaore N M M, Kaore S P N, et al. Utility of Chicago Sky Blue Stain in Rapid Diagnosis of Mycotic Infections[J]. National Journal of Laboratory Medicine, 2021.
[2] Favre-Besse F C, Poirel O, Bersot T, et al. Design, synthesis and biological evaluation of small-azo-dyes as potent Vesicular Glutamate Transporters inhibitors[J]. European Journal of Medicinal Chemistry, 2014, 78: 236-247.
[3] Risse E, Nicoll A J, Taylor W A, et al. Identification of a compound that disrupts binding of amyloid-β to the prion protein using a novel fluorescence-based assay[J]. Journal of Biological Chemistry, 2015, 290(27): 17020-17028.
[4] Pomierny B, Krzyżanowska W, Skórkowska A, et al. Inhibition of vesicular glutamate transporters (VGLUTs) with Chicago Sky Blue 6B before focal cerebral ischemia offers neuroprotection[J]. Molecular neurobiology, 2023, 60(6): 3130-3146.
[5] Yan S, Xuan Z, Yang M, et al. CSB6B prevents β-amyloid-associated neuroinflammation and cognitive impairments via inhibiting NF-κB and NLRP3 in microglia cells[J]. International Immunopharmacology, 2020, 81: 106263.
[6] Jin K, Zheng L, Ye L, et al. Chicago sky blue 6B (CSB6B), an allosteric inhibitor of macrophage migration inhibitory factor (MIF), suppresses osteoclastogenesis and promotes osteogenesis through the inhibition of the NF-κB signaling pathway[J]. Biochemical Pharmacology, 2021, 192: 114734.
[7] Min J O, Strohäker T, Jeong B C, et al. Chicago sky blue 6B inhibits α-synuclein aggregation and propagation[J]. Molecular brain, 2022, 15(1): 27.

Chicago Sky Blue 6B是荧光和免疫荧光组织化学中背景自发荧光的复染剂^[1]。Chicago Sky Blue 6B是一种有效的竞争性囊泡谷氨酸转运体1（VGLUT1）抑制剂，IC₅₀为3μM^[2]。Chicago Sky Blue 6B是第一个能够抑制Aβ结合的小分子PrP配体^[3]。Chicago Sky Blue 6B具有抗炎活性^[4]。

在体外，Chicago Sky Blue 6B（3.3-10μM）处理Aβ和脂多糖处理的BV2小胶质细胞1h，显著抑制了肿瘤坏死因子-α（TNF-α）、白细胞介素-1β（IL-1β）等促炎因子的产生^[5]。Chicago Sky Blue 6B（5、10、20μM）处理原代小鼠骨髓单核细胞/巨噬细胞（BMMs）5-7天，抑制了破骨细胞分化和骨吸收功能，抑制了早期NF-κB信号传导^[6]。

在体内，Chicago Sky Blue 6B（20mg/kg/day）处理A53T α-突触核蛋白转基因（Tg）小鼠3个月，挽救了Tg小鼠的运动协调缺陷，显著降低了Tg小鼠脑区域中S129-磷酸化α-突触核蛋白（pS129）水平和前额叶皮层中的胶质细胞酸性蛋白（GFAP）免疫反应性^[7]。