The effects of increased heme oxygenase-1 on the lymphoproliferative response in dogs with visceral leishmaniasis

Abstract

Canine visceral leishmaniasis (CVL) is known to affect the cellular immunity of infected dogs, through impairing lymphoproliferation and microbicidal mechanisms. This study examined heme oxygenase-1 (HO-1) and its metabolites, oxidative stress and IL-10 levels in CVL and investigated correlations between these parameters. Additionally, the effects of HO-1 inhibition on the lymphoproliferative response and cytokine production in lymph node cells (LNCs) from infected dogs were evaluated. Forty-four dogs, 24 controls and 20 dogs with CVL were selected. Plasma and splenic levels of HO-1, haptoglobin, soluble CD163 receptor, ferritin and IL-10 were determined using capture ELISA. The HO-1 levels and relative gene expression in peripheral blood and bone marrow mononuclear cells were also determined. LNCs proliferation was evaluated with an HO-1 activator and with an HO-1 inhibitor, in the presence of the Leishmania infantum soluble antigen (SAgL), using flow cytometry. HO-1, IL-2, IFN-gamma and IL-10 were also determined in these cultures using capture ELISA. Infected dogs presented oxidative stress and increased HO-1 levels and relative gene expression, with correlation between oxidative stress and HO-1. The substances from heme metabolism and IL-10 were also elevated in the plasma and spleens of infected dogs. IL-10 and HO-1 levels were positively correlated with one another. Inhibition of HO-1 increased LNCs proliferation and decreased IL-10 and IL-2 production in the presence of SAgL. The increased HO-1 metabolism observed in CVL is probably associated with oxidative stress and increased IL-10, which could be one of the mechanisms responsible for inhibition of the lymphoproliferative response in sick dogs.

Induction of haem oxygenase‐1 increases infection of dog macrophages by L. infantum

“…Recent studies have proposed that increased HO‐1 metabolism might be related to susceptibility to VL among humans and dogs . Similarly, we observed that induction of HO‐1 in macrophages from healthy dogs increased the infection rate and parasite load in these cells.…”

“…Not only was the percentage of infected human macrophages increased when these cells were treated with CoPP, but also the number of intracellular amastigotes and the viability of L. chagasi inside macrophages increased . It is reasonable to assume that the increase in HO‐1 metabolism observed in infected dogs that was recently described is one of the mechanisms responsible for the establishment and persistence of L. infantum infection in these animals. Corroborating this, our results demonstrated that induction of HO‐1 in macrophages from healthy dogs increased both the infection rate and the parasite load, such that there was even a positive correlation between these parameters and HO‐1 levels and gene expression.…”

“…To evaluate HO‐1 gene expression ( Hmox1 ), a previous protocol was used, with some modifications. RNA was extracted from 2 × 10 6 cells, and 300 ng of RNA was used for the reverse transcription (RT) reaction in a final volume of 20 μL.…”

“…In this regard, involvement of haem oxygenase‐1 (HO‐1), a stress‐inducible enzyme, has been correlated with human and canine susceptibility to VL. HO‐1 is responsible for conversion of haem into iron, carbon monoxide and biliverdin (which is rapidly converted into bilirubin) .…”

Hepcidin mediated iron homoeostasis as immune regulator in visceral leishmaniasis patients

“…Cellular stress by heme oxygenase-1, during L.chagasi infection has also been shown to be responsible for inflammatory imbalance 14 and inhibition of lymphoproliferative responses 15 thereby conferring disease susceptibility. Therefore, iron serves as double-edged sword- as a nutrient for pathogen and antimicrobial defense, becoming an important parameter in context of macrophage-residing Leishmania , determining the disease fate and how this balance is regulated by HPN has been a mystery in VL infection.…”