Department of Pediatrics, Case Western Reserve University/Rainbow Babies and Children's Hospital, Cleveland, Ohio 44106, USA.
Invest Ophthalmol Vis Sci. 2010 Mar;51(3):1699-708. doi: 10.1167/iovs.09-3557. Epub 2009 Oct 15.
Evidence suggests that capillary degeneration in early diabetic retinopathy results from chronic inflammation, and leukotrienes have been implicated in this process. The authors investigated the cellular sources of leukotriene biosynthesis in diabetic retinas and the effects of hyperglycemia on leukotriene production.
Retinas and bone marrow cells were collected from diabetic and nondiabetic mice. Mouse retinal glial cells and retinal endothelial cells (mRECs) were cultured under nondiabetic and diabetic conditions. Production of leukotriene metabolites was assessed by mass spectrometry, and Western blot analysis was used to quantitate the expression of enzymes and receptors involved in leukotriene synthesis and signaling.
Bone marrow cells from nondiabetic mice expressed 5-lipoxygenase, the enzyme required for the initiation of leukotriene synthesis, and produced leukotriene B(4) (LTB(4)) when stimulated with the calcium ionophore A23187. Notably, LTB(4) synthesis was increased threefold over normal (P < 0.03) in bone marrow cells from diabetic mice. In contrast, retinas from nondiabetic or diabetic mice produced neither leukotrienes nor 5-lipoxygenase mRNA. Despite an inability to initiate leukotriene biosynthesis, the addition of exogenous leukotriene A(4) (LTA(4); the precursor of LTB(4)) to retinas resulted in robust production of LTB(4). Similarly, retinal glial cells synthesized LTB(4) from LTA(4), whereas mRECs produced both LTB(4) and the cysteinyl leukotrienes. Culturing the retinal cells in high-glucose concentrations enhanced leukotriene synthesis and selectively increased expression of the LTB(4) receptor BLT1. Antagonism of the BLT1 receptor inhibited LTB(4)-induced mREC cell death.
Transcellular delivery of LTA(4) from marrow-derived cells to retinal cells results in the generation of LTB(4) and the death of endothelial cells and, thus, might contribute to chronic inflammation and retinopathy in diabetes.
有证据表明，早期糖尿病性视网膜病变中的毛细血管退化是由慢性炎症引起的，而白三烯与此过程有关。作者研究了糖尿病视网膜中白三烯生物合成的细胞来源，以及高血糖对白三烯产生的影响。
从糖尿病和非糖尿病小鼠中收集视网膜和骨髓细胞。在非糖尿病和糖尿病条件下培养小鼠视网膜神经胶质细胞和视网膜内皮细胞（mRECs）。通过质谱法评估白三烯代谢产物的产生，并用 Western blot 分析定量参与白三烯合成和信号转导的酶和受体的表达。
非糖尿病小鼠的骨髓细胞表达了 5-脂氧合酶，这是白三烯合成的起始酶，当用钙离子载体 A23187 刺激时，产生白三烯 B4（LTB4）。值得注意的是，糖尿病小鼠的骨髓细胞中 LTB4 的合成增加了三倍（P<0.03）。相比之下，非糖尿病或糖尿病小鼠的视网膜既不产生白三烯，也不产生 5-脂氧合酶 mRNA。尽管不能起始白三烯生物合成，但将外源性白三烯 A4（LTA4；LTB4 的前体）添加到视网膜中会导致大量 LTB4 的产生。同样，视网膜神经胶质细胞从 LTA4 合成 LTB4，而 mRECs 则产生 LTB4 和半胱氨酰白三烯。在高葡萄糖浓度下培养视网膜细胞会增强白三烯的合成，并选择性增加 LTB4 受体 BLT1 的表达。BLT1 受体拮抗剂抑制 LTB4 诱导的 mREC 细胞死亡。
骨髓细胞向视网膜细胞传递 LTA4 导致 LTB4 的产生以及内皮细胞的死亡，从而可能导致糖尿病中的慢性炎症和视网膜病变。
