Daisuke Shiva

The reduction of voluntary physical activity after poly I:C injection is independent of the effect of poly I:C-induced interferon-beta in mice.

One characteristic of sickness behavior in mice is demonstrated by a reduction in voluntary wheel-running activity during infection. Among synthetic double-stranded (ds) RNAs, polyriboinosinic: polyribocytidylic acid (poly I:C) activates to produce interferon (IFN) -beta, which plays an important role in anti-viral activity and host-defense. However, how voluntary wheel-running activity is regulated during poly I:C infection is unknown. To determine whether poly I:C-induced IFN-beta production is responsible for reduced spontaneous physical activity, we measured poly I:C-induced changes in voluntary wheel-running activity in mice. In this experiment, the mice were injected with poly I:C (0-5 mg/kg i.v.) and/or anti-IFN-beta neutralizing antibody (1.5x10(5) U/kg i.v.). We also observed the direct effect of injection of recombinant IFN-beta (rIFN-beta: 5.0x10(4) and 2.5x10(5) U/kg) on wheel-running behavior. Poly I:C treatment dose-dependently reduced wheel-running activity, and induced an increase in plasma IFN-beta in mice. However the activity was not attenuated by the neutralizing antibody specific to IFN-beta treatment. Additionally, the wheel-running activity in rIFN-beta treated mice was maintained, although they showed a higher IFN-gamma inducible protein (IP)-10 concentration in plasma compared with that of the vehicle group. Our results suggest that the transient reduction in physical activity after poly I:C injection is induced dose dependently, but that the mediator might not be poly I:C-induced IFN-beta.

Lipopolysaccharide-induced monocyte chemotactic protein-1 is enhanced by suppression of nitric oxide production, which depends on poor CD14 expression on the surface of skeletal muscle.

It is known that lipopolysaccharide (LPS)‐induced monocyte chemotactic protein (MCP)‐1 secretion from tissues recruits monocytes from the circulation, but the mechanism of the LPS‐induced MCP‐1 production in skeletal muscle is largely unexplained. To clarify the effect of LPS on MCP‐1 production in skeletal muscle cells, C2C12 cells from a mouse skeletal muscle cell line, and RAW 264.7 cells from a mouse macrophage cell line, were used to assess production of LPS‐induced MCP‐1, nitric oxide (NO) and interferon (IFN)‐β. In addition, we evaluated inducible NO synthases (iNOS) mRNA expression using RT‐PCR, and cell surface expression of CD14 and toll‐like receptor (TLR) 4 using flow cytometry. In C2C12 cells, LPS stimulation increased MCP‐1 production (p < 0.01), but combined treatment with LPS and NO inducer, diethylammonium (Z)‐1‐(N,N‐diethylamino) diazen‐1‐ium‐1,2‐diolate (NONOate), significantly inhibited its production (p < 0.01). LPS stimulation neither induced production of NO nor of IFN‐β, which is an NO inducer. Recombinant IFN‐β stimulation, on the other hand, enhanced LPS‐induced NO production (p < 0.01). Interestingly, we found that surface expression of CD14, which regulates IFN‐β production, in C2C12 cells was much lower than that in RAW 264.7 cells, although TLR4 expression on C2C12 cells was similar to that on RAW 264.7 cells. These data suggest that the reduced NO production in response to LPS may depend on low expression of CD14 on the cell surface of skeletal muscle, and that it may enhance LPS‐induced MCP‐1 production. Together, these functions of skeletal muscle could decrease the risk of bacterial infection by recruitment of monocytes. Copyright

High dose of lipopolysaccharide pre-treatment prevents OVA-induced anaphylactic decreases in rectal temperature in the immunized mice.

It remains unclear whether lipopolysaccharide (LPS) pre-treatment, which prevents Th2-type responses via Toll-like receptor 4 (TLR4), inhibits anaphylaxis. To determine the dose-dependent effects of LPS pre-treatment on anaphylactic decreases in rectal temperature caused by ovalbumin (OVA) re-exposure in immunized mice, C3H/HeN mice were divided into vehicle/OVA (0 mg/kg LPS), L-LPS/OVA (0.5 mg/kg LPS), M-LPS/OVA (1.0 mg/kg LPS) and H-LPS/OVA (3.0 mg/kg LPS) groups. After receiving these treatments, the mice were systemically immunized with OVA. Negative control mice were not immunized with OVA (N-OVA). After measuring the serum levels of OVA-specific IgE and IgG1 antibodies, the mice were examined for changes in their rectal temperature and plasma histamine concentration after OVA re-exposure. The allergen-specific IgE and IgG1 concentrations in sera from L-LPS/OVA, M-LPS/OVA and H-LPS/OVA mice were significantly lower than those in sera from vehicle/OVA mice despite OVA immunization. However, the antibody levels in all OVA-immunized mice, with the exception of the IgG1 levels in H-LPS/OVA mice, were significantly higher than those in N-OVA mice. Interestingly, H-LPS/OVA mice were the only group that did not exhibit a decrease in rectal temperature, since the rectal temperatures in vehicle/OVA, L-LPS/OVA and M-LPS/OVA mice were significantly decreased by OVA re-exposure. Furthermore, the decrease in rectal temperature after OVA re-exposure in L-LPS/OVA mice, which did not exhibit an increase in the plasma histamine concentration, was significantly prevented by treatment with a platelet-activating factor (PAF) receptor antagonist alone. Taken together, the present results indicate that high-dose LPS pre-treatment may prevent anaphylaxis in OVA-immunized mice, and that this mechanism may depend on inhibition of the IgG-PAF pathway rather than the IgE-histamine pathway.

α-Tocopheryl succinate induces rapid and reversible phosphatidylserine externalization in histiocytic lymphoma through the caspase-independent pathway

Phosphatidylserine (PS) externalization is a key feature of apoptotic cell death and plays an important role in clearance of apoptotic cells by phagocytes. PS externalization during apoptosis is generally an irreversible event mediated by caspase activation and is accompanied by other apoptotic events. We report here that an apoptosis inducer α-tocopheryl succinate (TOS) can induce PS externalization that is independent of apoptosis and reversible in the absence of fetal bovine serum (FBS) in histiocytic lymphoma U937 cells. In the presence of FBS, TOS induced PS externalization via a caspase-dependent mechanism accompanied by mitochondrial depolarization, cell shrinkage, increase of caspase-3 activity, and chromatin condensation. In contrast, in the absence of FBS, TOS induced the rapid PS externalization which was not accompanied by other apoptotic events. The PS externalization was reversible by removing TOS and was not involved in Ca2+-dependent scramblase activation and thiol oxidation of aminophospholipid translocase. A similar PS externalization was also induced by cholesteryl hemisuccinate (CS), the other succinate ester. These results suggested that the mechanism of TOS- and CS-induced PS externalization in the absence of FBS was different from it occurring during typical apoptosis.