Functional characterization of equine neutrophils in response to calcium ionophore A23187 and phorbol myristate acetate ex vivo

New Application of the Commercially Available Dye Celestine Blue B as a Sensitive and Selective Fluorescent “Turn-On” Probefor Endogenous Detection of HOCl and Reactive Halogenated Species

Hypochlorous acid (HOCl) derived from hydrogen peroxide and chloride anion by myeloperoxidase (MPO) plays a significant role in physiological and pathological processes. Herein we report a phenoxazine-based fluorescent probe Celestine Blue B (CB) that is applicable for HOCl detection in living cells and for assaying the chlorinating activity of MPO. A remarkable selectivity and sensitivity (limit of detection is 32 nM), along with a rapid “turn-on” response of CB to HOCl was demonstrated. Furthermore, the probe was able to detect endogenous HOCl and reactive halogenated species by fluorescence spectroscopy, confocal microscopy, and flow cytometry techniques. Hence, CB is a promising tool for investigating the role of HOCl in health and disease and for screening the drugs capable of regulating MPO activity.

Extracellular Reactive Oxygen Species (ROS) Production in Fresh Donkey Sperm Exposed to Reductive Stress, Oxidative Stress and NETosis

Jenny shows a large endometrial reaction after semen influx to the uterus with a large amount of polymorphonuclear neutrophils (PMN) migrating into the uterine lumen. PMN act as a sperm selection mechanism through phagocytosis and NETosis (DNA extrudes and, together with proteins, trap spermatozoa). While a reduced percentage of spermatozoa are phagocytosed by PMN, most are found to be attached to neutrophil extracellular traps (NETs). This selection process together with sperm metabolism produces a large amount of reactive oxygen species (ROS) that influence the reproductive success. The present study aimed to determine the extracellular ROS production in both sperm and PMN. With this purpose, (1) donkey sperm were exposed to reductive and oxidative stresses, through adding different concentrations of reduced glutathione (GSH) and hydrogen peroxide (H₂O₂), respectively; and (2) PMN were subjected to NETosis in the presence of the whole semen, sperm, seminal plasma (SP) or other activators such as formyl-methionyl-leucyl-phenylalanine (FMLP). Extracellular ROS production (measured as H₂O₂ levels) was determined with the Amplex^® Red Hydrogen Peroxide/Peroxidase Assay Kit. Donkey sperm showed more resilience to oxidative stress than to the reductive one, and GSH treatments led to greater H₂O₂ extracellular production. Moreover, not only did SP appear to be the main inducer of NETosis in PMN, but it was also able to maintain the extracellular H₂O₂ levels produced by sperm and NETosis.

Role of adrenoceptor-coupled second messenger system in sympatho-adrenomedullary modulation of splenic macrophage functions in live fish Channa punctatus

In order to understand the role of sympatho-adrenomedullary (SAM) system in mediating stress effect on non-specific immune responses in fishes, the splenic macrophage phagocytic and respiratory burst activities of normal and chemically sympathectomized Channa punctatus under restraint stress were studied. Chemical sympathectomy abrogated the differential effects of acute stress on diverse functions of macrophages. The SAM regulation of macrophage activities was substantiated by in vitro experiments with catecholamines, the end product of SAM system. Further, for the first time in fishes, different adrenoceptors and their precise second messenger system regulating diverse functions of macrophages by catecholamines were demonstrated. Norepinephrine (NE)/epinephrine (E) decreased the phagocytosis through beta-adrenergic receptor as only propranolol, the beta-adrenergic receptor antagonist, blocked the suppressive effect of NE/E. However, dopamine (DA) regulates phagocytosis solely via the dopaminergic receptor. The DA effect was mimicked by DA receptor agonists, apomorphine and bromocryptine. Adenylate cyclase system linked to beta-adrenoceptor/dopaminergic receptor seems to be involved in mediating the effect of catecholamine on phagocytosis since db cAMP inhibited the phagocytosis in a dose-dependent manner. In case of superoxide production, only phenoxybenzamine, an alpha-adrenergic receptor antagonist, was seen effective in blocking the stimulatory effect of NE/E. Further, Ca2+ as second messenger system coupled to alpha1-adrenergic receptor was shown to mediate this effect since phospholipase C (PLC) inhibitor, U73122 and intracellular calcium chelating agent, BAPTA-AM downregulated the NE/E-induced superoxide production. The role of calcium in modulation of superoxide production was also emphasized using calcium ionophore A23187.

A rapid and simple method for the separation of pure lymphocytes from horse blood

A method for the separation of pure and viable lymphocytes and granulocytes from the same blood sample in horses was reported. By centrifuging equine heparinized blood at 100 xg for 10 min at room temperature (r.t.), the resulting supernatant plasma was an almost pure (97.71 +/- 0.30%; n = 15) suspension of highly viable (98.72 +/- 0.28%) lymphocytes. When sodium citrate was used as an anticoagulant, lymphocyte suspensions collected in the same manner showed lower purity (87.89 +/- 1.59%; n = 9) and higher yields (56.56 +/- 3.89%, n = 9 versus 36.11 +/- 2.23%, n = 15). Where needed, a further centrifugation at 250 xg for 3 min (r.t.) of heparinized lymphocyte preparations removed an average of 87.39% (n = 15) contaminating platelets. A suspension of 85.96 +/- 2.20% pure granulocytes (93.23 +/- 1.74% neutrophils; n = 14) with minimal contamination by erythrocytes and high viability (93.11 +/- 1.26%) was obtained by performing a flash red blood cell lysis on the white-greyish layer resulting from the centrifugation of the heparinized blood samples. Among the several methods available, the procedure described herein is easy, rapid, cheap and reproducible.

Generation of reactive oxygen species by equine neutrophils and their effect on motility of equine spermatozoa

Contaminating leukocytes in the ejaculate are an important source of reactive oxygen species (ROS) in human semen. When present in sufficient numbers, they can have a detrimental influence on sperm function in humans. Unfortunately, there is little published information regarding the importance of leukocytes in stallion semen. The objectives of this study were to determine the production of hydrogen peroxide (H2O2) by activated equine neutrophils and to examine the effect of this ROS production on equine sperm motility in vitro. Motile equine spermatozoa (two ejaculates each from four stallions) and peripheral blood neutrophils were isolated on discontinuous Percoll gradients, washed and resuspended in a modified Tyrode's medium. Spermatozoa (25 x 10(6)/ml) were incubated for 30 min at 38 C with neutrophils (0,0.5 x 10(6),1 x 10(6), 5 x 10(6) and 10 x 10(6)/ml) activated by either the protein kinase C agonist, 12-myristate, 13-acetate phorbol ester (PMA; 100 nM) or the leukocyte chemotactic peptide, formyl-methionyl-leucyl-phenylalanine (FMLP; 0.1 mM). Sperm motility was determined by computer-assisted semen analysis (CASA) at time 0 min (T0) and time 30 min (T30), and H2O2 was measured at T30 with the Amplex Red assay kit. At T30, there was a significant (P < 0.01) increase in H2O2 with the addition of 5 x 10 and 10 x 10(6) neutrophils/ml activated by FMLP (0.76 +/- 0.3 and 0.99 +/- 0.4 microM, respectively, versus 0.0024 +/- 0.002 microM in sperm alone), and this increase was associated with a significant (P < 0.001) decrease in total motility (52 +/- 5.1 and 48 +/- 6.0%, respectively, versus 80 +/- 4.7% in sperm alone). At T30, there was also a significant (P < 0.001) increase in H2O2 with the addition of 5 x 10(6) and 10 x 10(6) neutrophils/ml activated by PMA (1.88 +/- 0.2 and 2.07 +/- 0.3 microM, respectively, versus 0.0009 +/- 0.0006 microM in sperm alone). The results of this study demonstrate that 5 x 10(6) activated neutrophils/ml are sufficient to impair equine sperm motility in vitro.