Alam Mohammad Samiul, Akaike Takaaki, Okamoto Shinichiro, Kubota Tatsuo, Yoshitake Jun, Sawa Tomohiro, Miyamoto Yoichi, Tamura Fumio, Maeda Hiroshi
Department of Microbiology, Kumamoto University School of Medicine, Kumamoto 860-0811, Japan.
Infect Immun. 2002 Jun;70(6):3130-42. doi: 10.1128/IAI.70.6.3130-3142.2002.
Host defense functions of nitric oxide (NO) are known for many bacterial infections. In this study, we investigated the antimicrobial effect of NO in murine salmonellosis by using inducible NO synthase (iNOS)-deficient mice infected with an avirulent or virulent Salmonella enterica serovar Typhimurium strain. All iNOS-deficient mice died of severe septicemia within 6 days after intraperitoneal injection with an avirulent strain (LT2) to which wild-type mice were highly resistant; 50% lethal doses (LD(50)s) of the LT2 strain for iNOS-deficient and wild-type mice were 30 CFU and 7 x 10(4) CFU, respectively. Lack of NO production in iNOS-deficient mice was verified directly by electron spin resonance spectroscopy. Bacterial yields in liver and blood were much higher in iNOS-deficient mice than in wild-type mice throughout the course of infection. Very small amounts of a virulent strain of serovar Typhimurium (a clinical isolate, strain Gifu 12142; LD(50), 50 CFU) given orally caused severe septicemia in iNOS-deficient animals; wild-type mice tolerated higher doses (LD(50), 6 x 10(2) CFU). Histopathology of livers from infected iNOS-deficient mice revealed extensive damage, such as diffuse hepatocellular apoptosis and increased neutrophil infiltration, but livers from infected wild-type mice showed a limited number of microabscesses, consisting of polymorphonuclear cells and macrophages and low levels of apoptotic change. The LT2 strain was much more susceptible to the bactericidal effect of peroxynitrite than the Gifu strain, suggesting that peroxynitrite resistance may contribute to Salmonella pathogenicity. These results indicate that NO has significant host defense functions in Salmonella infections not only because of its direct antimicrobial effect but also via cytoprotective actions for infected host cells, possibly through its antiapoptotic effect.
一氧化氮（NO）的宿主防御功能在许多细菌感染中都为人所知。在本研究中，我们通过使用感染无毒或有毒肠炎沙门氏菌鼠伤寒血清型菌株的诱导型一氧化氮合酶（iNOS）缺陷小鼠，研究了NO在鼠伤寒沙门氏菌病中的抗菌作用。所有iNOS缺陷小鼠在腹腔注射无毒菌株（LT2）后6天内死于严重败血症，而野生型小鼠对该菌株具有高度抗性；LT2菌株对iNOS缺陷小鼠和野生型小鼠的半数致死剂量（LD50）分别为30 CFU和7×10⁴ CFU。通过电子自旋共振光谱直接证实了iNOS缺陷小鼠中NO的产生缺乏。在整个感染过程中，iNOS缺陷小鼠肝脏和血液中的细菌产量远高于野生型小鼠。口服极少量的鼠伤寒血清型有毒菌株（临床分离株，岐阜12142株；LD50，50 CFU）会在iNOS缺陷动物中引起严重败血症；野生型小鼠能耐受更高剂量（LD50，6×10² CFU）。感染iNOS缺陷小鼠的肝脏组织病理学显示广泛损伤，如弥漫性肝细胞凋亡和中性粒细胞浸润增加，但感染野生型小鼠的肝脏显示出由多形核细胞和巨噬细胞组成的少量微脓肿，且凋亡变化水平较低。LT2菌株比岐阜菌株对过氧亚硝酸盐的杀菌作用更敏感，这表明过氧亚硝酸盐抗性可能有助于沙门氏菌的致病性。这些结果表明，NO在沙门氏菌感染中具有重要的宿主防御功能，不仅因为其直接抗菌作用，还通过对感染宿主细胞的细胞保护作用，可能是通过其抗凋亡作用。
