Inhibitor of C1q secretion suppresses the macrophage response to lipid A for nitric oxide but not for TNF production: evidence for a role of C1q in autocrine binding of TNF

Extracellular vesicles: Natural liver-accumulating drug delivery vehicles for the treatment of liver diseases

Extracellular vesicles (EVs) are excellent potential vectors for the delivery of therapeutic drugs. However, issues with biological safety and disease targeting substantially limit their clinical application. EVs from red blood cells (RBC-EVs) are potential drug delivery vehicles because of their unique biological safety. Here, we demonstrated that EVs, including RBC-EVs, show natural liver accumulation. Mechanistically, the liver environment induces macrophages to phagocytize RBC-EVs in a C1q-dependent manner. RBC-EVs loaded with antisense oligonucleotides of microRNA-155 showed macrophage-dependent protective effects against acute liver failure (ALF) in a mouse model. These RBC-EVs were also effective in treatment of ALF. Furthermore, compared to routine doses of doxorubicin and sorafenib (SRF), RBC-EVs loaded with doxorubicin or SRF showed enhanced therapeutic effects on a murine model of orthotopic liver cancer through a mechanism dependent on macrophages. Importantly, drug-loaded RBC-EVs showed no systemic toxicity at therapeutically effective doses, whereas routine doses of doxorubicin and SRF showed obvious toxicity. Thus, drug-loaded RBC-EVs hold high potential for clinical applications in the treatment of liver disease therapy.

Modulation of nitric oxide synthase activity in macrophages

L-Arginine is converted to the highly reactive and unstable nitric oxide (NO) and L-citrulline by an enzyme named nitric oxide synthase (NOS). NO decomposes into other nitrogen oxides such as nitrite (NO₂^-) and nitrate (NO₂^-), and in the presence of superoxide anion to the potent oxidizing agent peroxynitrite (ONOO⁻). Activated rodent macrophages are capable of expressing an inducible form of this enzyme (iNOS) in response to appropriate stimuli, i.e., lipopolysaccharide (LPS) and interferon-γ (IFNγ). Other cytokines can modulate the induction of NO biosynthesis in macrophages. NO is a major effector molecule of the anti-microbial and cytotoxic activity of rodent macrophages against certain micro-organisms and tumour cells, respectively. The NO synthesizing pathway has been demonstrated in human monocytes and other cells, but its role in host defence seems to be accessory. A delicate functional balance between microbial stimuli, host-derived cytokines and hormones in the microenvironment regulates iNOS expression. This review will focus mainly on the known and proposed mechanisms of the regulation of iNOS induction, and on agents that can modulate NO release once the active enzyme has been expressed in the macrophage.

Role of peroxynitrite and activation of poly (ADP-ribose) synthase in the vascular failure induced by zymosan-activated plasma

1. Zymosan is a wall component of the yeast Saccharomyces Cerevisiae. Injection of zymosan into experimental animals is known to produce an intense inflammatory response. Recent studies demonstrated that the zymosan-induced inflammatory response in vivo can be ameliorated by inhibitors of nitric oxide (NO) biosynthesis. The cytotoxic effects of NO are, in part, mediated by the oxidant preoxynitrite and subsequent activation of the nuclear enzyme poly (ADP-ribose) synthetase (PARS). In the present in vitro study, we have investigated the cellular mechanisms of vascular failure elicited by zymosan-activated plasma and the contribution of peroxynitrite production and activation of PARS to the changes. 2. Incubation of rat aortic smooth muscle cells with zymosan-activated plasma (ZAP) induced the production of nitrite, the breakdown product of NO, due to the expression of the inducible isoform of NO synthase (iNOS) over 6 24 h. In addition, ZAP triggered the production of peroxynitrite in these cells, as measured by the oxidation of the fluorescent dye dihydrorhodamine 123 and by nitrotyrosine Western blotting. 3. Incubation of the smooth muscle cells with ZAP induced DNA single strand breakage and PARS activation. These effects were reduced by inhibition of NOS with NG-methyl-L-arginine (L-NMA, 3 mM), and by glutathione (3 mM), a scavenger of peroxynitrite. The PARS inhibitor 3-aminobenzamide (1 mM) inhibited the ZAP-induced activation of PARS. 4. Incubation of thoracic aortae with ZAP in vitro caused a reduction of the contractions of the blood vessels to noradrenaline (vascular hyporeactivity) and elicited a reduced responsiveness to the endothelium-dependent vasodilator acetylcholine (endothelial dysfunction). 5. Preincubation of the thoracic aortae with L-NMA (1 mM), glutathione (3 mM) or by the PARS inhibitor 3-aminobenzamide (1 mM) prevented the development of vascular hyporeactivity in response to ZAP. Moreover, glutathione and 3-aminobenzamide treatment protected against the ZAP-induced development of endothelial dysfunction. The PARS-related loss of the vascular contractility was evident at 30 min after incubation in endothelium-intact, but not in endothelium-denuded vessels and also manifested at 6 h after incubation with ZAP in endothelium-denuded rings. The acute response is probably related, therefore, to peroxynitrite formation (involving the endothelial NO synthase), whereas the delayed response may be related to the expression of iNOS in the smooth muscle. 6. The data obtained suggest that zymosan-activated plasma causes vascular dysfunction by inducing the simultaneous formation of superoxide and NO. These radicals combine to form peroxynitrite, which, in turn causes DNA injury and PARS activation. The protective effect of 3-aminobenzamide demonstrates that PARS activation contributes both to the development of vascular hyporeactivity and endothelial dysfunction during the vascular failure induced by ZAP.

Autocrine induction of macrophage synthesis of complement subcomponent C1q by endogenous interferon-alpha/beta

Peritoneal macrophages (M phi) constitutively synthesize and secrete interferon-alpha (IFN-alpha) and IFN-beta, as well as complement subcomponent C1q. Because exogenous interferon-gamma (IFN-gamma) stimulates Mø synthesis of C1q, our purpose was to determine if endogenous secretion of IFN-alpha/beta regulated the constitutive level of endogenous C1q mRNA synthesis in an autocrine fashion. Both exogenous IFN-alpha and IFN-beta effectively substituted for IFN-gamma in stimulating M phi C1q mRNA expression in a dose-dependent fashion by northern blot analysis. Neutralizing anti-INF-alpha/beta antibodies inhibited M phi constitutive C1q mRNA synthesis by approximately twofold and abrogated the feedback stimulatory effects of exogenous C1q on C1q mRNA expression. Paraffin oil-elicited inflammatory M phi displayed distinctively different constitutive levels of C1q mRNA expression from thioglycollate brothelicited M phi, which was correlated with their relative levels of secretory IFN-alpha/beta by ELISA. Exogenous IFN-alpha/beta also restored C1q mRNA synthesis of AKR mouse M phi with low constitutive C1q mRNA expression. The cumulative results support the concept that constitutive synthesis of C1q by M phi is regulated by the endogenous synthesis and secretion of IFN-alpha/beta, which appears to act in an autocrine fashion.

Lipid A and the lipid A analogue anti-tumour compound ONO-4007 induce nitric oxide synthase in vitro and in vivo

The ability of lipid A and the antitumour compound, ONO-4007 (sodium2-deoxy-2-[3S-(9-phenylnonanoyloxy)tetradecanoyl] amino-3-O-(9phenylnonanoyl)-D-glucopyranose 4-sulphate) to induce nitric oxide (NO) synthase was investigated in vitro and in vivo, in comparison to the effects of lipopolysaccharide and di- and monophosphoryl lipid A. In J744.2 macrophages, lipopolysaccharide, di-and monophosphoryl lipid A and ONO-4007 (10(-9) - 10(-5) g/ml) alone, or in combination with interferon-gamma, induced NO synthase (order of potency: lipopolysaccharide > diphosphoryl lipid A > monophosphoryl lipid A > ONO-4007). ONO-4007 increased the activity of the inducible NO synthase in the lung of anesthetised rats (20% of the increased caused by bacterial lipopolysaccharide). Thus, ONO-4007 is a weak inducer of the inducible isoform of NO synthase in vitro and in vivo. The finding that di- and monophosphoryl lipid A also induce NO synthase indicates that the lipid A moiety of lipopolysaccharide contributes to the induction of NO synthase by lipopolysaccharide. The induction of NO synthase by ONO-4007, resulting in the formation of cytotoxic NO may contribute to the antitumour activity of the compound.

Complement activation in amyloid plaques in Alzheimer's disease brains does not proceed further than C3

In Alzheimer's disease (AD) patients, the complement components Clq, C4 and C3 can be detected in different types of beta/A4 plaques, one of the hallmarks of AD. Contradictory findings on the presence of late complement components in AD brains have been reported. Nevertheless, it was suggested in recent studies that in AD brain complement activation results in complement membrane attack complex (MAC) formation and that complement activation may act as an intermediate between beta/A4 deposits and the neurotoxicity observed in AD. In the present study the presence of a number of complement components and regulatory proteins in AD temporal cortex and, for comparison, in glomerulonephritis (GN) was analysed. In GN kidneys, besides Clq, Clr, Cls and C3, the late components and the C5b-9 complex are also associated with capillary basement membrane and mesangial immune complex deposits. In AD temporal cortex Clq, C4 and C3 are co-localized with beta/A4 deposits. However, in contrast to the GN kidney, the late complement components C5, C7 and C9, as well as the C5b-9 membrane attack complex cannot be detected in beta/A4 positive plaques. The absence of the cytolytic C5b-9 complex in AD brain suggests that in AD, the complement MAC does not function as the proposed inflammatory mediator between beta/A4 deposits and the neurofibrillary changes.