Vector Group, Liverpool School of Tropical Medicine, Liverpool, United Kingdom.
PLoS One. 2011 Mar 9;6(3):e17486. doi: 10.1371/journal.pone.0017486.
The phlebotomine sand fly Lutzomyia longipalpis is the most important vector of American visceral leishmaniasis (AVL), the disseminated and most serious form of the disease in Central and South America. In the natural environment, most female L. longipalpis are thought to survive for less than 10 days and will feed on blood only once or twice during their lifetime. Successful transmission of parasites occurs when a Leishmania-infected female sand fly feeds on a new host. Knowledge of factors affecting sand fly longevity that lead to a reduction in lifespan could result in a decrease in parasite transmission. Catalase has been found to play a major role in survival and fecundity in many insect species. It is a strong antioxidant enzyme that breaks down toxic reactive oxygen species (ROS). Ovarian catalase was found to accumulate in the developing sand fly oocyte from 12 to 48 hours after blood feeding. Catalase expression in ovaries as well as oocyte numbers was found to decrease with age. This reduction was not found in flies when fed on the antioxidant ascorbic acid in the sugar meal, a condition that increased mortality and activation of the prophenoloxidase cascade. RNA interference was used to silence catalase gene expression in female Lu. longipalpis. Depletion of catalase led to a significant increase of mortality and a reduction in the number of developing oocytes produced after blood feeding. These results demonstrate the central role that catalase and ROS play in the longevity and fecundity of phlebotomine sand flies.
白蛉属沙蝇卢氏长尾舌蝇是美洲内脏利什曼病（AVL）最重要的传播媒介，也是中美洲和南美洲传播最广、最严重的疾病形式。在自然环境中，大多数雌性卢氏长尾舌蝇的寿命不到 10 天，一生中只会吸血一到两次。当感染寄生虫的雌性沙蝇叮咬新宿主时，寄生虫就会成功传播。了解影响沙蝇寿命的因素，从而缩短其寿命，可能会减少寄生虫的传播。过氧化氢酶在许多昆虫物种的生存和繁殖中都起着重要作用。它是一种强大的抗氧化酶，可以分解有毒的活性氧物质（ROS）。研究发现，卵巢过氧化氢酶在吸血后 12 至 48 小时内会在发育中的沙蝇卵母细胞中积累。随着年龄的增长，卵巢中的过氧化氢酶表达以及卵母细胞数量会减少。然而，当这些苍蝇在糖餐中摄入抗氧化剂抗坏血酸时，这种情况会增加死亡率并激活酚氧化酶原级联反应，因此不会出现这种减少。RNA 干扰被用来沉默雌性卢氏长尾舌蝇中的过氧化氢酶基因表达。过氧化氢酶的耗竭导致死亡率显著增加，并减少吸血后产生的发育中的卵母细胞数量。这些结果表明，过氧化氢酶和 ROS 在白蛉属沙蝇的寿命和繁殖力中起着核心作用。
