Impaired febrile responses of aging mice are mediated by endogenous lipocortin-1 (annexin-1)

Eicosapentaenoic acid changes muscle transcriptome and intervenes in aging-related fiber type transition in male mice

Age-related sarcopenia is associated with a variety of changes in skeletal muscle. These changes are interrelated with each other and associated with systemic metabolism, the details of which, however, are largely unknown. Eicosapentaenoic acid (EPA) is a promising nutrient against sarcopenia and has multifaceted effects on systemic metabolism. In this study, we hypothesized that the aging process in skeletal muscle can be intervened by the administration of EPA. Seventy-five-week-old male mice were assigned to groups fed an EPA-deprived diet (EPA-) or an EPA-enriched diet with 1 wt% EPA (EPA+) for 12 wk. Twenty-four-week-old male mice fed with normal chow were also analyzed. At baseline, the grip strength of the aging mice was lower than that of the young mice. After 12 wk, EPA+ showed similar muscle mass but increased grip strength compared with EPA-. EPA+ displayed higher insulin sensitivity than EPA-. Immunohistochemistry and gene expression analysis of myosin heavy chains (MyHCs) revealed fast-to-slow fiber type transition in aging muscle, which was partially inhibited by EPA. RNA sequencing (RNA-Seq) analysis suggested that EPA supplementation exerts pathway-specific effects in skeletal muscle including the signatures of slow-to-fast fiber type transition. In conclusion, we revealed that aging skeletal muscle in male mice shows lower grip strength and fiber type changes, both of which can be inhibited by EPA supplementation irrespective of muscle mass alteration.NEW & NOTEWORTHY This study demonstrated that the early phenotype of skeletal muscle in aging male mice is characterized by muscle weakness with fast-to-slow fiber type transition, which could be ameliorated by feeding with EPA-enriched diet. EPA induced metabolic changes such as an increase in systemic insulin sensitivity and altered muscle transcriptome in the aging mice. These changes may be related to the fiber type transition and influence muscle quality.

Annexin A1 translocates to nucleus and promotes the expression of pro-inflammatory cytokines in a PKC-dependent manner after OGD/R

Annexin A1 (ANXA1) is a protein known to have multiple roles in the regulation of inflammatory responses. In this study, we find that after oxygen glucose deprivation/reoxygenation (ODG/R) injury, activated PKC phosphorylated ANXA1 at the serine 27 residue (p27S-ANXA1), and promoted the translocation of p27S-ANXA1 to the nucleus of BV-2 microglial cells. This in turn induced BV-2 microglial cells to produce large amounts of pro-inflammatory cytokines. The phenomenon could be mimicked by either transfecting a mutant form of ANXA1 with its serine 27 residue converted to aspartic acid, S27D, or by using the PKC agonist, phorbol 12-myristate 13-acetate (PMA) in these microglial cells. In contrast, transfecting cells with an ANXA1 S27A mutant (serine 27 converted to alanine) or treating the cells with the PKC antagonist, GF103209X (GF) reversed this effet. Our study demonstrates that ANXA1 can be phosphorylated by PKC and is subsequently translocated to the nucleus of BV-2 microglial cells after OGD/R, resulting in the induction of pro-inflammatory cytokines.

Annexin 1: the new face of an old molecule

The annexin superfamily consists of 13 calcium or calcium and phospholipid binding proteins with a significant degree of biological and structural homology (40-60%). First described in the late 1970s and subsequently referred to as macrocortin, renocortin, lipomodulin, lipocortin-1, and more recently Annexin 1, this 37 kDa calcium and phospholipid binding protein is a strong inhibitor of glucocorticoid-induced eicosanoid synthesis and PLA2. Recent interest in the biological activity of this intriguing molecule has unraveled important functional attributes of Annexin 1 in a variety of inflammatory pathways, on cell proliferation machinery, in the regulation of cell death signaling, in phagocytic clearance of apoptosing cells, and most importantly in the process of carcinogenesis. Here we attempt to present a short review on these diverse biological activities of an interesting and important molecule, which could be a potential target for novel therapeutic intervention in a host of disease states.

Effect of annexin-1 on experimental autoimmune encephalomyelitis (EAE) in the rat

Annexin-1, a calcium-dependent phospholipid binding protein, has been shown to act as an endogenous central neuroprotectant, notably against cerebral ischaemic damage. In the present study we extend these findings to an animal model of multiple sclerosis, EAE, and report that endogenous annexin-1 is expressed in ED1+ macrophages and resident astrocytes localized within the lesions in the central nervous system (CNS). Intracerebroventricular (i.c.v.) administration of an NH2-terminal fragment spanning amino acids 1-188 of annexin-1 after the onset of the clinical symptoms significantly reduced both the neurological severity as well as weight loss of mild EAE. Immunoneutralization of endogenous brain annexin-1 failed to exacerbate the clinical features of EAE. Thus, although the role of endogenous annexin-1 in the pathogenesis of EAE remains to be determined, our findings suggest that annexin-1 may be of therapeutic benefit to the treatment of multiple sclerosis.

Acute inflammatory response in the mouse: exacerbation by immunoneutralization of lipocortin 1

1. An immuno-neutralization strategy was employed to investigate the role of endogenous lipocortin 1 (LC1) in acute inflammation in the mouse. 2. Mice were treated subcutaneously with phosphate-buffered solution (PBS), non-immune sheep serum (NSS) or with one of two sheep antisera raised against LC1 (LCS3), or its N-terminal peptide (LCPS1), three times over a period of seven days. Twenty four hours after the last injection several parameters of acute inflammation were measured including zymosan-induced inflammation in 6-day-old air-pouches, zymosan-activated serum (ZAS)-induced oedema in the skin, platelet-activating factor (PAF)-induced neutrophilia and interleukin-1 beta (IL-1 beta)-induced corticosterone (CCS) release. 3. At the 4 h time-point of the zymosan inflamed air-pouch model, treatment with LCS3 did not modify the number of polymorphonuclear leucocytes (PMN) recruited: 7.84 +/- 1.01 and 7.00 +/- 0.77 x 10(6) PMN per mouse for NSS- and LCS3 group, n = 7. However, several other parameters of cell activation including myeloperoxidase (MPO) and elastase activities were increased (2.2 fold, P < 0.05, and 6.5 fold, P < 0.05, respectively) in the lavage fluids of these mice. Similarly, a significant increase in the amount of immunoreactive prostaglandin E2 (PGE2; 1.81 fold, P < 0.05) and IL-1 alpha (2.75 fold, P < 0.05), but not tumour necrosis factor-alpha (TNF-alpha), was also observed in LCS3-treated mice. 4. The recruitment of PMN into the zymosan inflamed air-pouches by 24 h had declined substantially (4.13 +/- 0.61 x 10(6) PMN per mouse, n = 12) in the NSS-treated mice, whereas high values were still measured in those treated with LCS3 (9.35 +/- 1.20 x 10(6) PMN per mouse, n = 12, P < 0.05). A similar effect was also found following sub-chronic treatment of mice with LCPS1: 6.48 +/- 0.10 x 10(6) PMN per mouse, vs. 2.77 +/- 1.20 and 2.64 +/- 0.49 x 10(6) PMN per mouse for PBS- and NSS-treated groups (n = 7, P < 0.05). Most markers of inflammation were also increased in the lavage fluids of LCS3-treated mice: MPO and elastase showed a 2.47 fold and 17 fold increase, respectively (P < 0.05 in both cases); TNF-alpha showed a 11.1 fold increase (P < 0.05) whereas the IL-1 alpha levels were not significantly modified. PGE2 was still detectable in most (5 out of 7) of the mice treated with LCS3 but only in 2 out of 7 of the NSS-treated mice. 5. Intradermal injection of 50% ZAS caused a significant increase in the 2 hoedema formation in the skin of LCS3-treated mice in comparison to PBS- and NSS-treated animals: 16.7 +/- 1.5 microliters vs. 10.8 +/- 1.2 microliters and 10.2 +/- 1.0 microliters, respectively (n = 14 mice per group, P < 0.05). ZAS-induced oedema had subsided by 24 h in control animals but a residual significant amount of extravasation was still detectable in LCS3-treated mice: 4.4 +/- 0.8 microliters (P < 0.05). 6. A recently described model driven by endogenous glucocorticoids is the blood neutrophilia observed following administration of PAF. In our experimental conditions, a single bolus of PAF (100 ng, i.v.) provoked a marked neutrophilia at 2 h (2.43 and 2.01 fold) in NSS- and PBS-treated mice (n = 11), respectively, which was significantly attenuated in the animals treated with LCS3: 1.26 fold increase in circulating PMN (n = 11, P < 0.01 vs. NSS- and PBS-groups). 7. Intraperitoneal injection of IL-1 beta (5 micrograms kg-1) caused a marked increase in circulating plasma CCS by 2 h, to a similar extent in all experimental groups. In contrast, measurement of CCS levels in the plasma of mice bearing air-pouches inflamed with zymosan revealed significant differences between LCS3 and NSS-treated mice at the 4 h time-point: 198 +/- 26 ng ml-1 vs. 110 +/- 31 ng ml-1 (n = 8, P < 0.05). 8. In conclusion, we found a remarkable exacerbation of the inflammatory process with respect to both humoral and cellular components in mice passively immunised agains