In vitro evaluation of the effect of a novel immunosuppressive agent, FTY720, on the function of feline neutrophils

The Role of Sphingolipids and Sphingosine-1-phosphate-Sphingosine-1-phosphate-receptor Signaling in Psoriasis

Psoriasis is a long-lasting skin condition characterized by redness and thick silver scales on the skin's surface. It involves various skin cells, including keratinocytes, dendritic cells, T lymphocytes, and neutrophils. The treatments for psoriasis range from topical to systemic therapies, but they only alleviate the symptoms and do not provide a fundamental cure. Moreover, systemic treatments have the disadvantage of suppressing the entire body's immune system. Therefore, a new treatment strategy with minimal impact on the immune system is required. Recent studies have shown that sphingolipid metabolites, particularly ceramide and sphingosine-1-phosphate (S1P), play a significant role in psoriasis. Specific S1P-S1P-receptor (S1PR) signaling pathways have been identified as crucial to psoriasis inflammation. Based on these findings, S1PR modulators have been investigated and have been found to improve psoriasis inflammation. This review will discuss the metabolic pathways of sphingolipids, the individual functions of these metabolites, and their potential as a new therapeutic approach to psoriasis.

Inhibition of Human Neutrophil Functions In Vitro by Multiple Sclerosis Disease-Modifying Therapies

There is a growing optimism about the potential of new disease-modifying therapies (DMTs) in the management of relapsing-remitting multiple sclerosis (RRMS) patients. However, this initial enthusiasm has been tempered by evidence indicating that multiple sclerosis (MS) patients undergoing DMT may be at higher risk of developing infections through incompletely understood mechanisms. As neutrophils provide the first line of defense against pathogens, here we have compared the effects of some of the commonly used MS DMTs (i.e., moderate-efficacy injective, first-line: interferonβ-1b (IFNβ-1b), glatiramer acetate (GA); and high-efficacy, second-line: fingolimod (FTY) and natalizumab (NAT)) on the in vitro viability and functions of neutrophils isolated from healthy subjects. All the DMTs tested impaired the ability of neutrophils to kill Klebsiella pneumoniae, whereas none of them affected the rate of neutrophil apoptosis or CD11b and CD62L cell surface expression. Intriguingly, only FTY exposure negatively affected K. pneumoniae-induced production of reactive oxygen species (ROS) in polymorphonuclear leukocytes (PMNs). Furthermore, neutrophils exposed to K. pneumoniae secreted enhanced amounts of CXCL8, IL-1β and TNF-α, which were differentially regulated following DMT pretreatment. Altogether, these findings suggest that DMTs may increase the susceptibility of MS patients to microbial infections, in part, through inhibition of neutrophil functions. In light of these data, we recommend that the design of personalized therapies for RRMS patients should take into account not just the mechanism of action of the chosen DMT but also the potential risk of infection associated with the administration of such therapeutic compounds to this highly vulnerable population.

Hyposialylated α1-acid glycoprotein inhibits phagocytosis of feline neutrophils

Feline α1-acid glycoprotein (fAGP) modifies both its serum concentration and its glycan moiety during diseases. fAGP is hyposialylated in cats with feline infectious peritonitis (FIP), but not in clinically healthy cats or in cats with other diseases. This study was aimed to determine whether hyposialylated fAGP influences phagocytosis. A flow cytometric method based on ingestion of fluoresceinated bacteria and adapted to feline blood was used to assess phagocytosis of leukocytes incubated with 'non-pathological' fAGP (purified from sera with normal concentrations of AGP) and 'pathological' fAGP (purified from sera with >1.5mg/mL hyposialylated AGP). The flow cytometric method provided repeatable results for neutrophils (coefficients of variations, CVs <15%) but not for monocytes (CVs>20%) which had also a high individual variability. Compared with saline solution and with non-pathological fAGP, pathological fAGP significantly decreased phagocytosis in neutrophils and monocytes. This study demonstrated that hyposialylated fAGP down-regulates the phagocytic activity of feline neutrophils.

Oral pharmacokinetic and pharmacodynamic effects of FTY720 in cats

The aim of the study was to determine pharmacokinetic and pharmacodynamic profiles of FTY720 in cats and identify any toxic side effects. Six adult cats were used for the experimental study. Single oral dosages were tested at 0.05, 0.3 and 1.0 mg/kg. Whole blood drug concentration, total white blood cell and differential counts were monitored. Flow cytometry evaluated the effects on lymphocyte subsets. A toxicity study consisted of cats receiving a dose of 0.15 mg/kg daily for 30 days. Daily observation, physical examination and bloodwork were evaluated to assess for toxicity. All single doses resulted in > or =80% reduction in circulating lymphocytes within 12 h after administration, with the duration of lymphopenia being dose dependent. CD4+ and CD5+ T cells were specifically depleted. Peripheral neutrophils declined by approximately 70% at all dosages tested. No other toxic side effects were observed. Results of this study suggest that FTY720 is effective at inducing a peripheral lymphopenia in cats without any toxic side effects. Currently, cats appear to be the only species in which FTY720 induces a neutropenia. This study provides the foundation for future clinical transplantation trials using FTY720 in cats. By using combination therapy of FTY720 and low dose cyclosporine, the incidence of serious side effects may be reduced while still preventing allograft rejection.