Departamento de Parasitología, Universidad de Costa Rica, San José, Costa Rica.
PLoS Negl Trop Dis. 2008;2(10):e318. doi: 10.1371/journal.pntd.0000318. Epub 2008 Oct 15.
Envenomations by the snake Bothrops asper represent a serious medical problem in Central America and parts of South America. These envenomations concur with drastic local tissue pathology, including a prominent edema. Since lymph flow plays a role in the maintenance of tissue fluid balance, the effect of B. asper venom on collecting lymphatic vessels was studied.
METHODOLOGY/PRINCIPAL FINDINGS: B. asper venom was applied to mouse mesentery, and the effects were studied using an intravital microscopy methodology coupled with an image analysis program. B. asper venom induced a dose-dependent contraction of collecting lymphatic vessels, resulting in a reduction of their lumen and in a halting of lymph flow. The effect was reproduced by a myotoxic phospholipase A(2) (PLA(2)) homologue isolated from this venom, but not by a hemorrhagic metalloproteinase or a coagulant thrombin-like serine proteinase. In agreement with this, treatment of the venom with fucoidan, a myotoxin inhibitor, abrogated the effect, whereas no inhibition was observed after incubation with the peptidomimetic metalloproteinase inhibitor Batimastat. Moreover, fucoidan significantly reduced venom-induced footpad edema. The myotoxic PLA(2) homologue, known to induce skeletal muscle necrosis, was able to induce cytotoxicity in smooth muscle cells in culture and to promote an increment in the permeability to propidium iodide in these cells.
CONCLUSIONS/SIGNIFICANCE: Our observations indicate that B. asper venom affects collecting lymphatic vessels through the action of myotoxic PLA(2)s on the smooth muscle of these vessels, inducing cell contraction and irreversible cell damage. This activity may play an important role in the pathogenesis of the pronounced local edema characteristic of viperid snakebite envenomation, as well as in the systemic biodistribution of the venom, thus representing a potential therapeutical target in these envenomations.
在中美洲和南美洲部分地区，蛇 Bothrops asper 的咬伤是一个严重的医学问题。这些咬伤与剧烈的局部组织病理学有关，包括明显的水肿。由于淋巴流在维持组织液平衡中起作用，因此研究了 B. asper 毒液对收集淋巴管的作用。
方法/主要发现：将 B. asper 毒液应用于小鼠肠系膜，并使用活体显微镜方法结合图像分析程序研究其效果。B. asper 毒液诱导收集淋巴管的剂量依赖性收缩，导致其管腔缩小和淋巴流动停止。这种效应可以通过从这种毒液中分离出的一种肌毒性磷脂酶 A2（PLA2）同工酶重现，但不能通过一种出血性金属蛋白酶或一种凝血酶样丝氨酸蛋白酶重现。与此一致的是，用褐藻聚糖，一种肌毒素抑制剂，处理毒液可消除这种效应，而在用肽模拟金属蛋白酶抑制剂 Batimastat 孵育后则观察不到抑制作用。此外，褐藻聚糖可显著减少毒液引起的足垫水肿。已知引起骨骼肌坏死的肌毒性 PLA2 同工酶能够诱导培养中的平滑肌细胞产生细胞毒性，并促进这些细胞对碘化丙啶的通透性增加。
结论/意义：我们的观察结果表明，B. asper 毒液通过肌毒性 PLA2s 对这些血管的平滑肌作用来影响收集淋巴管，诱导细胞收缩和不可逆的细胞损伤。这种活性可能在响尾蛇咬伤毒液引起的明显局部水肿的发病机制中起重要作用，并且在毒液的全身分布中起作用，因此在这些毒液中毒中代表一个潜在的治疗靶点。
