original article Serum paraoxonase activity, total thiols levels, and oxidative status in patients with acute brucellosis 1 1 3 Summary It is well known that paraoxonase-1 (PON1) activity may decrease during the course of infection and infammation. Te aim of this study was to investigate serum PON1 activity, oxidative status, and thiols levels in patients with acute brucellosis. In addition, we inves- tigated the PON1 phenotype in patients with acute bru- cellosis. Tirty patients with acute brucellosis and 35 healthy controls were enrolled. Serum paraoxonase and arylesterase activities, thiols levels, lipid hydroperoxide levels, total antioxidant capacity (TAC), total oxidant status (TOS) and oxidative stress index (OSI) were deter- mined. Serum basal and salt-stimulated paraoxonase– arylesterase activities, TAC levels and thiols levels were signifcantly lower in patients with acute brucellosis than controls (for all, p < 0.05), while LOOH levels, TOS levels, and OSI values were signifcantly higher (for all, p < 0.05). We concluded that oxidative stress is increased, while serum PON1 activity is decreased in patients with acute brucellosis. Tese results indicate that lower PON1 activ- ity is associated with oxidant–antioxidant imbalance. Keywords Acute brucellosis · PON1 activity · Total anti- oxidant capacity · Total oxidant status · Oxidative stress index · Tiol Introduction Brucellosis is a zoonosis widely distributed in rural Mediterranean areas [1]. Te vast majority of cases are attributed to the subtype Brucella melitensis [2]. It is a small gram-negative, facultative intracellular pathogenic bacterium which is able to surviving and replicate within the cells of the mononuclear phagocytic system [3]. In humans, brucellosis is a systemic infection, which may involve any organ or system of the body [1]. It has been demonstrated that in the many infectious diseases, a variety of infammatory cells are activated, which lead to production of reactive oxygen species (ROS) to kill intracellular and extracellular parasites [4]. ROS are one of the crucial molecules that kill bacteria internalized into phagocytic cells, such as polymorpho- nuclear neutrophils and macrophages [5]. Brucellae invade macrophages during the early phase of infection, adapt to the acidic environment, and proliferate in the vacuolar compartments [6]. It has been stated that the oxidative killing pathways of host macrophages represent a primary mechanism utilized by these host phagocytes to control the intracellular replication of the brucellae [7]. Furthermore, it has been shown that brucellosis is related to increased free radical production and anti- oxidant depletion. Tus, oxidative stress has been impli- cated in the pathogenesis of brucellosis [8]. Paraoxonase 1 (PON1) is a 354 amino acid Ca 2 + -depen- dent serum esterase that is synthesized in the liver. Te enzyme has both arylesterase and paraoxonase activities [9]. Human serum PON1 is an enzyme associated with high-density lipoprotein (HDL) that prevents oxida- tive modifcation of low-density lipoprotein (LDL) [10]. Dr. M. Aslan () · R. Esen · M. E. Kucukoglu Medical Faculty, Department of Internal Medicine, Yuzuncu Yıl University, 65000 Van, Turkey e-mail: m.aslan301@mynet.com A. Cıkman Medical Faculty, Department of Microbiology, Yuzuncu Yıl University, Van, Turkey U. Yakan · M. Sunnetcioglu Medical Faculty, Department of Infectious Disease and Clinical Microbiology, Yuzuncu Yıl University, Van, Turkey S. Selek Medical Faculty, Department of Clinical Biochemistry, Bezmialem Vakif University, Istanbul, Turkey Received: 2 September 2014 / Accepted: 19 January 2015 © Springer-Verlag Wien 2015 Wien Klin Wochenschr DOI 10.1007/s00508-015-0720-z Serum paraoxonase activity, total thiols levels, and oxidative status in patients with acute brucellosis Ramazan Esen · Mehmet Aslan · Mehmet Emin Kucukoglu · Aytekin Cıkman · Umit Yakan · Mahmut Sunnetcioglu · Sahbettin Selek