Spontaneous Necrotizing Hepatic Arteriopathy in Male Sprague-Dawley Rats.

Differentiating test article-related vascular changes from spontaneous findings is important for microscopic interpretation in drug safety evaluation studies intended for regulatory submission. Here, we report background spontaneous hepatic artery degeneration and necrosis in up to 20% of 3- to 9-month-old control male Sprague-Dawley rats in 23 individual safety studies. The vascular degeneration occurred in one cross section of a medium-sized hepatic artery near the hilus and ranged from acute intramural hemorrhage and fibrinoid necrosis to chronic fibrosis of the vascular wall with perivascular edema, hemorrhage, and inflammatory cell infiltrates. The cause was uncertain. Many microscopic features were consistent with systemic necrotizing arteriopathy (SNA) or polyarteritis; however, there was no change in arteries commonly affected in SNA/polyarteritis (mesenteric, pancreatic, or testicular arteries) and hepatic artery degeneration/necrosis occurred in younger rats which is unusual for SNA/polyarteritis. Spontaneous hepatic artery degeneration/necrosis represents a sporadic background finding that may be confused with a test article's toxicologic effect.

Changes in the major cell envelope components of Mycobacterium tuberculosis during in vitro growth.

One-third of the world's population is infected with Mycobacterium tuberculosis (M.tb), which causes tuberculosis. Mycobacterium tuberculosis cell envelope components such as glycolipids, lipoglycans and polysaccharides play important roles in bacteria-host cell interactions that dictate the host immune response. However, little is known about the changes in the amounts and types of these cell envelope components as the bacillus divides during in vitro culture. To shed light on these phenomena, we examined growth-dependent changes over time in major cell envelope components of virulent M.tb by using sodium dodecyl sulfate-polyacrylamide gel electrophoresis, thin-layer chromatography, mass spectrometry, immunoblotting and flow cytometry. Our studies provide evidence that major mannosylated glycoconjugates on the M.tb cell envelope change as M.tb grows in vitro on the widely used Middlebrook 7H11 agar. In particular, our compositional analyses show that from Day 9 to 28 the amounts of mannose-containing molecules, such as mannose-capped lipoarabinomannan, lipomannan and phosphatidyl-myo-inositol mannosides, change continuously in both the cell envelope and outer cell surface. Along with these changes, mannan levels on the outer cell surface also increase significantly over time. The implications of these differences in terms of how M.tb is grown for studies performed in vitro and in vivo for assessing M.tb-host recognition and establishment of infection are discussed.

Mycobacterium tuberculosis lipomannan blocks TNF biosynthesis by regulating macrophage MAPK-activated protein kinase 2 (MK2) and microRNA miR-125b.

Contact of Mycobacterium tuberculosis (M.tb) with the immune system requires interactions between microbial surface molecules and host pattern recognition receptors. Major M.tb-exposed cell envelope molecules, such as lipomannan (LM), contain subtle structural variations that affect the nature of the immune response. Here we show that LM from virulent M.tb (TB-LM), but not from avirulent Myocobacterium smegmatis (SmegLM), is a potent inhibitor of TNF biosynthesis in human macrophages. This difference in response is not because of variation in Toll-like receptor 2-dependent activation of the signaling kinase MAPK p38. Rather, TB-LM stimulation leads to destabilization of TNF mRNA transcripts and subsequent failure to produce TNF protein. In contrast, SmegLM enhances MAPK-activated protein kinase 2 phosphorylation, which is critical for maintaining TNF mRNA stability in part by contributing microRNAs (miRNAs). In this context, human miRNA miR-125b binds to the 3' UTR region of TNF mRNA and destabilizes the transcript, whereas miR-155 enhances TNF production by increasing TNF mRNA half-life and limiting expression of SHIP1, a negative regulator of the PI3K/Akt pathway. We show that macrophages incubated with TB-LM and live M.tb induce high miR-125b expression and low miR-155 expression with correspondingly low TNF production. In contrast, SmegLM and live M. smegmatis induce high miR-155 expression and low miR-125b expression with high TNF production. Thus, we identify a unique cellular mechanism underlying the ability of a major M.tb cell wall component, TB-LM, to block TNF biosynthesis in human macrophages, thereby allowing M.tb to subvert host immunity and potentially increase its virulence.

Racism in the electronic age: Role of online forums in expressing racial attitudes about American Indians.

This study investigated racial attitudes about American Indians that are electronically expressed in newspaper online forums by examining the University of North Dakota's Fighting Sioux nickname and logo used for their athletic teams. Using a modified Consensual Qualitative Research (CQR) methodology to analyze over 1,000 online forum comments, the research team generated themes, domains, and core ideas from the data. The core ideas included (a) surprise, (b) power and privilege, (c) trivialization, and (d) denigration. The findings indicated that a critical mass of online forum comments represented ignorance about American Indian culture and even disdain toward American Indians by providing misinformation, perpetuating stereotypes, and expressing overtly racist attitudes toward American Indians. Results of this study were explained through the lens of White power and privilege, as well as through the framework of two-faced racism (Picca & Feagin, 2007). Results provide support to previous findings that indicate the presence of Native-themed mascots, nicknames, or logos can negatively impact the psychological well-being of American Indians.

Critical role of amino acid position 343 of surfactant protein-D in the selective binding of glycolipids from Mycobacterium tuberculosis.

Surfactant protein D (SP-D), a lectin that recognizes carbohydrates via its C-type carbohydrate recognition domains (CRDs), regulates Mycobacterium tuberculosis (M.tb)-macrophage interactions via recognition of M.tb mannosylated cell wall components. SP-D binds to, agglutinates, and reduces phagocytosis and intracellular growth of M.tb. Species-specific variations in the CRD amino acid sequence contribute to carbohydrate recognition preferences and have been exploited to enhance the antimicrobial properties of SP-D in vitro. Here, we characterized the binding interaction between several wild-type and mutant SP-D neck + CRD trimeric subunits (NCRDs) and pathogenic and nonpathogenic mycobacterial species. Specific amino acid substitutions (i.e., the 343-amino-acid position) that flank the carbohydrate binding groove led to significant increases in binding of only virulent and attenuated M.tb strains and to a lesser extent M. marinum, whereas there was negligible binding to M. avium complex and M. smegmatis. Moreover, a nonconserved mutation at the critical 321-amino-acid position (involved in Ca(2+) coordination) abrogated binding to M.tb and M. marinum. We further characterized the binding of NCRDs to the predominant surface-exposed mannosylated lipoglycans of the M.tb cell envelope. Results showed a binding pattern that is dependent on the nature of the side chain of the 343-amino-acid position flanking the SP-D CRD binding groove and the nature of the terminal mannosyl sugar linkages of the mycobacterial lipoglycans. We conclude that the 343 position is critical in defining the binding pattern of SP-D proteins to M.tb and its mannosylated cell envelope components.

Lack of CXCR3 delays the development of hepatic inflammation but does not impair resistance to Leishmania donovani.

CXC chemokine receptor 3 (CXCR3) ligands CXCL9 and CXCL10 are produced at high levels in mice and humans infected with Leishmania donovani, but their contribution to host resistance against L. donovani is not clear. Here, using CXCR3(-/-) mice, we demonstrate that, although CXCR3 regulates early immune cell trafficking and hepatic inflammation during L. donovani infection, it is not essential for immunity against L. donovani, unlike L. major. CXCR3(-/-) C57BL/6 mice show a delayed onset of hepatic inflammation and granuloma formation after L. donovani infection. However, they mount an efficient T helper cell type 1 response, recruit T cells to the liver, and control parasite growth as efficiently as do CXCR3(+/+) C57BL/6 mice.