The role of homocysteine and methylenetetrahydrofolate reductase, methionine synthase, methionine synthase reductase polymorphisms in the development of cardiovascular diseases and hypertension

Cardiovascular diseases (CVDs) are the leading causes of death in the developed countries. Elevated homocysteine level is as an independent risk factor of CVDs. The C677T and A1298C variants of methylenetetrahydrofolate reductase gene (MTHFR) have been shown to influence folate and homocysteine metabolisms. However, the relationship between MTHFR polymorphisms and hyperhomocysteinemia has not been well established yet. The gene variants were also reported to be associated with CVDs. In addition, the C677T polymorphisms may play a role in the development of hypertension. Recent research evidence has suggested that MTHFR variants might be independently linked to CVDs and hypertension, because of the involvement of the MTHFR enzyme product (5-methyl-tetrahydrofolate /5-MTHF) in the regulation of endothelial functions. Further research is required to investigate the association between gene polymorphisms of folate-metabolizing enzymes and CVDs, and to identify the possible role of the relevant gene variants in the molecular pathogenesis of hyperhomocysteinemia.     

Higher anti-TNF serum levels are associated with perianal fistula closure in Crohn’s disease patients

Objectives: Anti-TNF agents are effective to treat perianal Crohn’s disease (CD). Evidence suggests that Crohn’s disease patients with perianal fistulas need higher infliximab (IFX) serum concentrations compared to patients without perianal CD to achieve complete disease control. Our aim was to compare anti-TNF serum concentrations between patients with actively draining and closed perianal fistulas.

Methods: A retrospective survey was performed in CD patients with perianal disease treated with IFX or adalimumab (ADL). Fistula closure was defined as absence of active drainage at gentle finger compression and/or fistula healing on magnetic resonance imaging.

Results: We identified 66?CD patients with a history of perianal fistulas treated with IFX (n?=?47) and ADL (n?=?19). Median IFX serum trough concentrations ([interquartile range]) were higher in patients with closed fistulas (n?=?32) compared to patients with actively draining fistulas (n?=?15): 6.0?µg/ml [5.4–6.9] versus 2.3?µg/ml [1.1–4.0], respectively (p?<?.001)). A similar difference was seen in patients treated with ADL: median serum concentrations were 7.4?µg/ml [6.5–10.8] in 13 patients with closed fistulas versus 4.8?µg/ml [1.7–6.2] in 6 patients with producing fistulas (p?=?.003). Serum concentrations of ≥5.0?µg/ml for IFX (area under the curve of 0.92; 95% CI: 0.82–1.00)) and 5.9?µg/ml for ADL (area under the curve of 0.89; 95% CI 0.71–1.00) were associated with fistula closure.

Conclusion: Cut-off serum concentrations ≥5.0?µg/ml for IFX and ≥5.9?µg/ml for ADL were associated with perianal fistula closure. Hence, patients with producing perianal fistulas may benefit from anti-TNF dose intensification to achieve fistula closure.     

The Src family kinases Hck,Fgr, and Lyn are critical for the generation of the in vivo inflammatory environment without a direct role in leukocyte recruitment

Although Src family kinases participate in leukocyte function in vitro, such as integrin signal transduction, their role in inflammation in vivo is poorly understood. We show that Src family kinases play a critical role in myeloid cell–mediated in vivo inflammatory reactions. Mice lacking the Src family kinases Hck, Fgr, and Lyn in the hematopoietic compartment were completely protected from autoantibody-induced arthritis and skin blistering disease, as well as from the reverse passive Arthus reaction, with functional overlap between the three kinases. Though the overall phenotype resembled the leukocyte recruitment defect observed in β₂ integrin–deficient (CD18^−/−) mice, Hck^−/−Fgr^−/−Lyn^−/− neutrophils and monocytes/macrophages had no cell-autonomous in vivo or in vitro migration defect. Instead, Src family kinases were required for the generation of the inflammatory environment in vivo and for the release of proinflammatory mediators from neutrophils and macrophages in vitro, likely due to their role in Fcγ receptor signal transduction. Our results suggest that infiltrating myeloid cells release proinflammatory chemokine, cytokine, and lipid mediators that attract further neutrophils and monocytes from the circulation in a CD18-dependent manner. Src family kinases are required for the generation of the inflammatory environment but not for the intrinsic migratory ability of myeloid cells.Src family kinases are best known for their role in malignant transformation and tumor progression, as well as signaling through cell surface integrins (Parsons and Parsons, 2004; Playford and Schaller, 2004). Due to their role in cancer development and progression, Src family kinases have become major targets of cancer therapy (Kim et al., 2009; Zhang and Yu, 2012). Src family kinases are also present in immune cells with dominant expression of Lck and Fyn in T cells and NK cells; Lyn, Fyn, and Blk in B cells and mast cells; and Hck, Fgr, and Lyn in myeloid cells such as neutrophils and macrophages (Lowell, 2004).The best known function of Src family kinases in the immune system is their role in integrin signal transduction. Indeed, Hck, Fgr, and Lyn mediate outside-in signaling by β₁ and β₂ integrins in neutrophils and macrophages (Lowell et al., 1996; Meng and Lowell, 1998; Mócsai et al., 1999; Suen et al., 1999; Pereira et al., 2001; Giagulli et al., 2006; Hirahashi et al., 2006), Lck participates in LFA-1–mediated T cell responses (Morgan et al., 2001; Fagerholm et al., 2002; Feigelson et al., 2001; Suzuki et al., 2007), and Src family kinases are required for LFA-1–mediated signal transduction and target cell killing by NK cells (Riteau et al., 2003; Perez et al., 2004).Src family kinases also mediate TCR signal transduction by phosphorylating the TCR-associated immunoreceptor tyrosine-based activation motifs (ITAMs), leading to recruitment and activation of ZAP-70 (van Oers et al., 1996; Zamoyska et al., 2003; Palacios and Weiss, 2004). However, their role in receptor-proximal signaling by the BCR and Fc receptors is rather controversial. Although the combined deficiency of Lyn, Fyn, and Blk results in defective BCR-induced NF-κB activation, receptor-proximal BCR signaling (ITAM phosphorylation) is not affected (Saijo et al., 2003). Genetic deficiency of Lyn, the predominant Src family kinase in B cells, even leads to enhanced BCR signaling and B cell–mediated autoimmunity (Hibbs et al., 1995; Nishizumi et al., 1995; Chan et al., 1997). Similarly, both positive (Hibbs et al., 1995; Nishizumi and Yamamoto, 1997; Parravicini et al., 2002; Gomez et al., 2005; Falanga et al., 2012) and negative (Kawakami et al., 2000; Hernandez-Hansen et al., 2004; Odom et al., 2004; Gomez et al., 2005; Falanga et al., 2012) functions for Fyn and Lyn during Fc receptor signaling in mast cells have been reported. In addition, Hck^−/−Fgr^−/− neutrophils respond normally to IgG immune complex–induced activation (Lowell et al., 1996) and Fc receptor–mediated phagocytosis of IgG-coated red blood cells is delayed but not blocked in Hck^−/−Fgr^−/−Lyn^−/− macrophages (Fitzer-Attas et al., 2000; Lowell, 2004). The differential requirement for Src family kinases in TCR, BCR, and Fc receptor signaling is thought to derive from the fact that Syk, but not ZAP-70, is itself able to phosphorylate ITAM tyrosines (Rolli et al., 2002), making Src family kinases indispensable for signaling by the ZAP-70–coupled TCR but not by the Syk-coupled BCR and Fc receptors.Autoantibody production and immune complex formation is one of the major mechanisms of autoimmunity-induced tissue damage. In vivo models of those processes include the K/B×N serum transfer arthritis (Korganow et al., 1999) and autoantibody-induced blistering skin diseases (Liu et al., 1993; Sitaru et al., 2002, 2005), which mimic important aspects of human rheumatoid arthritis, bullous pemphigoid, and epidermolysis bullosa acquisita. Activation of neutrophils or macrophages (Liu et al., 2000; Wipke and Allen, 2001; Sitaru et al., 2002, 2005; Solomon et al., 2005), recognition of immune complexes by Fcγ receptors (Ji et al., 2002; Sitaru et al., 2002, 2005), and β₂ integrin–mediated leukocyte recruitment (Watts et al., 2005; Liu et al., 2006; Chiriac et al., 2007; Monach et al., 2010; Németh et al., 2010) are indispensable for the development of those in vivo animal models.The role of Src family kinases in β₂ integrin signaling and the requirement for β₂ integrins during autoantibody-induced in vivo inflammation prompted us to test the role of Src family kinases in autoantibody-induced inflammatory disease models. We found that Hck^−/−Fgr^−/−Lyn^−/− mice were completely protected from autoantibody-induced arthritis and inflammatory blistering skin disease. Surprisingly, this was not due to a cell-autonomous defect in β₂ integrin–mediated leukocyte migration but to defective generation of an inflammatory microenvironment, likely due to the role of Src family kinases in immune complex–induced neutrophil and macrophage activation.     

Nachweis gruppenspezifischer Substanzen im Knochengewebe durch Elution

Ohne Zusammenfassung     

Activation of a D2 receptor increases electrical coupling between retinal horizontal cells by inhibiting dopamine release.

In the fish retina, interplexiform cells release dopamine onto cone-driven horizontal cells. Dopamine decreases the electrical coupling between horizontal cells by activating adenylate cyclase through dopamine D1 receptors. Using intracellular recording, we have studied the effect of dopamine D2 receptor activation on horizontal cell electrical coupling in the intact goldfish retina. Superfusion of the D2 agonist LY171555 (quinpirole; 0.2-10 microM) increased horizontal cell coupling, as indicated by a decrease in responses to centered spots or slits of light. The length constant of the horizontal cell network increased an average of 31%. Although dopamine (0.5-20 microM) uncoupled horizontal cells, lower concentrations (e.g., 0.2 microM) initially uncoupled and then subsequently increased coupling beyond initial control levels. The coupling effect of LY171555 (10 microM) was blocked completely by prior application of the D1 agonist SKF 38393 at saturating (20 microM) or nonsaturating (2.5-5.0 microM) doses. Prior treatment of the retinas with 6-hydroxydopamine, which destroyed dopaminergic neurons, eliminated the coupling effect of LY171555 but not the uncoupling effect of SKF 38393. These results suggest that goldfish horizontal cells contain D1, but not D2, receptors and that dopamine activation of D2 autoreceptors on interplexiform cells inhibits dopamine release onto horizontal cells so that the electrical coupling between horizontal cells increases.     

Optimising the structure and function of the adult P23H-3 retina by light management in the juvenile and adult

This study tests the potential of light restriction to optimise retinal structure and function in adulthood, using the P23H-3 rhodopsin-mutant transgenic rat as a model. P23H-3 rats were reared in scotopic (5 lux) or mesopic (40–60 lux) cyclic (12 h/12 h light/dark) light. A further 2 groups were reared in one of these light conditions to P(postnatal day)30, and then were transferred to the other condition. Retinae were examined at P30-365. Rod and cone function were assessed by the dark-adapted flash electroretinogram. The rate of photoreceptor death was assessed with the TUNEL technique, and photoreceptor survival by the thickness of the outer nuclear layer (ONL). Photoreceptor structural changes were assessed by immunohistochemistry. Mesopic rearing severely reduced the number, function and outer segment (OS) length of photoreceptors. Light restriction in the adult (achieved by moving mesopic-reared animals to scotopic conditions at P30) slowed photoreceptor death, induced recovery of the ERG and of OS length in survivors, resulting in an adult retina that matched the scotopic-reared in function, photoreceptor survival (stability) and structure. Conversely, light exposure in the adult (achieved by moving scotopic-reared animals to mesopic conditions at P30) accelerated photoreceptor death, shortened OSs and reduced the ERG, resulting in a retina that was as damaged and dysfunctional as a mesopic-reared retina, and showed greater photoreceptor instability. Present observations suggest, that the stability and function of adult photoreceptors are determined by both early and adult ambient light experience. Light restriction in the adult was effective in inducing the self-repair of photoreceptors, and the recovery of their function and stability. Light restriction in the juvenile (before P30) improved early photoreceptor survival but made adult photoreceptors vulnerable to brighter light experienced in adulthood. For comparable human dystrophies, these results suggest that light restriction begun after retinal maturation may be effective in optimising the structure, function and stability of the adult retina.