Gladstone Institute of Neurological Disease, 1650 Owens St., San Francisco, CA 94158, USA.
J Neuroinflammation. 2012 Jan 24;9:22. doi: 10.1186/1742-2094-9-22.
Microglia, the resident immune cells of the brain, have been implicated in brain injury and various neurological disorders. However, their precise roles in different pathophysiological situations remain enigmatic and may range from detrimental to protective. Targeting the delivery of biologically active compounds to microglia could help elucidate these roles and facilitate the therapeutic modulation of microglial functions in neurological diseases.
Here we employ primary cell cultures and stereotaxic injections into mouse brain to investigate the cell type specific localization of semiconductor quantum dots (QDs) in vitro and in vivo. Two potential receptors for QDs are identified using pharmacological inhibitors and neutralizing antibodies.
In mixed primary cortical cultures, QDs were selectively taken up by microglia; this uptake was decreased by inhibitors of clathrin-dependent endocytosis, implicating the endosomal pathway as the major route of entry for QDs into microglia. Furthermore, inhibiting mannose receptors and macrophage scavenger receptors blocked the uptake of QDs by microglia, indicating that QD uptake occurs through microglia-specific receptor endocytosis. When injected into the brain, QDs were taken up primarily by microglia and with high efficiency. In primary cortical cultures, QDs conjugated to the toxin saporin depleted microglia in mixed primary cortical cultures, protecting neurons in these cultures against amyloid beta-induced neurotoxicity.
These findings demonstrate that QDs can be used to specifically label and modulate microglia in primary cortical cultures and in brain and may allow for the selective delivery of therapeutic agents to these cells.
小胶质细胞是大脑中的固有免疫细胞，它们与脑损伤和各种神经紊乱有关。然而，它们在不同病理生理情况下的具体作用仍不清楚，其作用范围可能从有害到保护。将生物活性化合物靶向递送至小胶质细胞有助于阐明这些作用，并促进神经疾病中小胶质细胞功能的治疗性调节。
我们采用原代细胞培养和立体定位注射到小鼠脑内来研究半导体量子点（QD）在体外和体内的细胞类型特异性定位。使用药理学抑制剂和中和抗体鉴定了两个潜在的 QD 受体。
在混合原代皮质培养物中，QD 被小胶质细胞选择性摄取；用网格蛋白依赖性内吞抑制剂处理后，QD 的摄取减少，表明内体途径是 QD 进入小胶质细胞的主要途径。此外，抑制甘露糖受体和巨噬细胞清道夫受体可阻止 QD 被小胶质细胞摄取，表明 QD 摄取是通过小胶质细胞特异性受体内吞作用发生的。当注射到脑内时，QD 主要被小胶质细胞摄取，摄取效率高。在原代皮质培养物中，与毒素 saporin 偶联的 QD 耗尽了混合原代皮质培养物中的小胶质细胞，从而保护这些培养物中的神经元免受淀粉样β诱导的神经毒性。
这些发现表明 QD 可用于特异性标记和调节原代皮质培养物以及脑内的小胶质细胞，并可能允许将治疗剂选择性递送至这些细胞。
