Microenvironmental Scenario of the Bone Marrow of Inorganic Arsenic-Exposed Experimental Mice

Arsenic Exposure Impairs Intestinal Stromal Cells

Arsenic is a toxicant commonly found in drinking water. Even though its main route of exposure is oral, little is known of the impact of in vivo arsenic exposure on small intestine. In vitro studies have shown that arsenic decreases differentiation of stem and progenitor cells in several different tissues. Thus, small intestinal organoids were used to assess if arsenic exposure would also impair intestinal stem cell differentiation. Unexpectedly, no changes in markers of differentiated epithelial cells were seen. However, exposing mice to 100 ppb arsenic in drinking water for 5 weeks impaired distinct populations of intestinal stromal cells. Arsenic reduced the width of the pericryptal lamina propria by 1.6-fold, and reduced Pdgfra mRNA expression, which is expressed in intestinal telocytes and trophocytes, by 4.2-fold. The height or extension of Pdgfra⁺ telopodes into the villus tip was also significantly reduced. Transcript expression of several other stromal cell markers, such as Grem1, Gli, CD81, were reduced by 1.9-, 2.3-, and 1.4-fold, respectively. Further, significant correlations exist between levels of Pdgfra and Gli1, Grem1, and Bmp4. Our results suggest arsenic impairs intestinal trophocytes and telocytes, leading to alterations in the Bmp signaling pathway.

Cellular and Molecular Mechanisms of Environmental Pollutants on Hematopoiesis

Hematopoiesis is a complex and intricate process that aims to replenish blood components in a constant fashion. It is orchestrated mostly by hematopoietic progenitor cells (hematopoietic stem cells (HSCs)) that are capable of self-renewal and differentiation. These cells can originate other cell subtypes that are responsible for maintaining vital functions, mediate innate and adaptive immune responses, provide tissues with oxygen, and control coagulation. Hematopoiesis in adults takes place in the bone marrow, which is endowed with an extensive vasculature conferring an intense flow of cells. A myriad of cell subtypes can be found in the bone marrow at different levels of activation, being also under constant action of an extensive amount of diverse chemical mediators and enzymatic systems. Bone marrow platelets, mature erythrocytes and leukocytes are delivered into the bloodstream readily available to meet body demands. Leukocytes circulate and reach different tissues, returning or not returning to the bloodstream. Senescent leukocytes, specially granulocytes, return to the bone marrow to be phagocytized by macrophages, restarting granulopoiesis. The constant high production and delivery of cells into the bloodstream, alongside the fact that blood cells can also circulate between tissues, makes the hematopoietic system a prime target for toxic agents to act upon, making the understanding of the bone marrow microenvironment vital for both toxicological sciences and risk assessment. Environmental and occupational pollutants, therapeutic molecules, drugs of abuse, and even nutritional status can directly affect progenitor cells at their differentiation and maturation stages, altering behavior and function of blood compounds and resulting in impaired immune responses, anemias, leukemias, and blood coagulation disturbances. This review aims to describe the most recently investigated molecular and cellular toxicity mechanisms of current major environmental pollutants on hematopoiesis in the bone marrow.

Preparation and anti-Raji lymphoma efficacy of a novel pH sensitive and magnetic targeting nanoparticles drug delivery system

BACKGROUND

Non-Hodgkin's lymphoma (NHL) is a heterogeneous class of cancers that arises in lymph nodes or other lymphatic tissues, which causes many deaths worldwide and its incidence is increasing.

METHODS

In this study, a pH-responsive DMSA-Fe₃O₄ magnetic nanoparticles (MNPs) covalently connect with ADM and As₂O₃ as a drug delivery system was invented to discuss the anticancer efficacy in non-Hodgkin's lymphoma (NHL) cell line--Raji.

RESULTS

Detailedly, according to the chelation of ADM and Fe²⁺, the release rate of ADM was accelerated in acidic environment, and slowed down/blocked in neutral environment. The inhibitory effect to induce apoptosis of Fe₃O₄/As₂O₃+Doxil on Raji cells was obvious compared with that of single-drug group. Furthermore, the expression of Bcl-2 gene in Raji cells was suppressed under the action of MNPs.

CONCLUSION

Taken together, the novel pH-responsive MNPs was proven to be a promising synergistic form of magnetic targeted drugs for clinical treatment of human Raji lymphoma.

Aberrant Wnt Signaling Pathway in the Hematopoietic Stem/Progenitor Compartment in Experimental Leukemic Animal

The evolutionarily conserved Wnt signaling pathway regulates physiological hematopoiesis, a process of formation of blood cells and has been shown to play crucial role in the development of both myeloid and lymphoid malignancies. The Wnt signaling pathway can be broadly divided into canonical and non-canonical pathways. In the present study, we investigated the pathobiology of leukemia by studying the expression profile of Wnt proteins, receptors, key signaling intermediates and endogenous Wnt antagonist involved in canonical and non-canonical pathways in the bone marrow (BM) hematopoietic stem/progenitor cell (HSPC) compartment of experimental leukemic mice. Cell adhesion molecule N-Cadherin and leukemic BM microenvironment with reference to Wnt were also studied. We used ENU, a potent carcinogen, to induce leukemia in wild type Swiss albino mice and malignant transformation was cofirmed by peripheral blood and BM studies. Flow cytometric expression analysis revealed profound up-regulation of canonical Wnt3a/β-catenin/CyclinD1 signaling axis along with N-Cadherin whereas down-regulation of non-canonical Wnt5a/Ca2+/CaMKII signaling axis in the leukemic HSPC compartment. Subsequent use of anti-Wnt3a antibody in the in vitro clonogenicity assay uncovered that anti-Wnt3a antibody preferentially inhibited the growth and number of the primitive leukemic hematopoietic CFU-GEMM and BFU-E colonies. Stromal cells derived from the leukemic BM also exhibited aberrant Wnt3a and Wnt5a protein expression. Taken together, alteration of canonical and non-canonical Wnt signaling pathways in the HSPC compartment along with classical Wnt protein expression pattern in the leukemic stromal microenvironment resulted in progression of leukemia.