Arsenite Selectively Inhibits Mouse Bone Marrow Lymphoid Progenitor Cell Development In Vivo and In Vitro and Suppresses Humoral Immunity In Vivo

Abstract

It is known that exposure to As+3 via drinking water causes a disruption of the immune system and significantly compromises the immune response to infection. The purpose of these studies was to assess the effects of As+3 on bone marrow progenitor cell colony formation and the humoral immune response to a T-dependent antigen response (TDAR) in vivo. In a 30 day drinking water study, mice were exposed to 19, 75, or 300 ppb As+3. There was a decrease in bone marrow cell recovery, but not spleen cell recovery at 300 ppb As+3. In the bone marrow, As+3 altered neither the expression of CD34+ and CD38+ cells, markers of early hematopoietic stem cells, nor CD45−/CD105+, markers of mesenchymal stem cells. Spleen cell surface marker CD45 expression on B cells (CD19+), T cells (CD3+), T helper cells (CD4+) and cytotoxic T cells (CD8+), natural killer (NK+), and macrophages (Mac 1+) were not altered by the 30 day in vivo As+3 exposure. Functional assays of CFU-B colony formation showed significant selective suppression (p<0.05) by 300 ppb As+3 exposure, whereas CFU-GM formation was not altered. The TDAR of the spleen cells was significantly suppressed at 75 and 300 ppb As+3. In vitro studies of the bone marrow revealed a selective suppression of CFU-B by 50 nM As+3 in the absence of apparent cytotoxicity. Monomethylarsonous acid (MMA+3) demonstrated a dose-dependent and selective suppression of CFU-B beginning at 5 nM (p<0.05). MMA+3 suppressed CFU-GM formation at 500 nM, a concentration that proved to be nonspecifically cytotoxic. As+5 did not suppress CFU-B and/or CFU-GM in vitro at concentrations up to 500 nM. Collectively, these results demonstrate that As+3 and likely its metabolite (MMA+3) target lymphoid progenitor cells in mouse bone marrow and mature B and T cell activity in the spleen.

Arsenite Interacts with Dibenzo[def,p]chrysene (DBC) at Low Levels to Suppress Bone Marrow Lymphoid Progenitors in Mice

“…2c, 2d). These findings are consistent with our previous studies showing the selective suppression of CFU-B in mouse BM following 30 day low level As +3 exposures [6]. …”

“…Because we previously found that MMA +3 (an As +3 metabolite) may be responsible for the toxicity of As +3 on BM in vivo [6], we investigated possible interaction of MMA +3 with DBC or DBC-diol in in vitro cultures, using one concentration (5 nM) that was previously establshed to be minimally toxic to the BM and another at a ten times lower concentration (0.5 nM). Both concentrations of MMA +3 suppressed CFU-B formation in mouse BM (Fig 3b).…”

“…Bone marrow cells were isolated according to the procedure outlined in the Stem Cell Technologies Technical Manual version 3.1.1 (http://www.stemcell.com/) and as described in previous work [6]. Briefly, each mouse was euthanized and the femurs were sterilely harvested, then placed and held on ice in Hanks' Balanced Salt Solution (HBSS) from Lonza Walkersville, MD, and transported to the laboratory.…”

“…Our previous studies showed that As +3 given orally at low levels selectively suppressed bone marrow (BM) lymphoid progenitor cells responses in vivo and in vitro , and spleen T-dependent antibody responses (TDAR) in vitro [6]. Immunosuppression is one of the major adverse manifestations of As +3 and PAH exposures.…”

“…Concentrations of 19 and 75 ppb As +3 in 30 day drinking water were previously established to be non-toxic to the BM [6], and 0.1 and 1 mg/kg cumulative doses of DBC in pill forms [10] were chosen based on previous dose-range studies.…”