Chitosan polyplex mediated delivery of miRNA-124 reduces activation of microglial cells in vitro and in rat models of spinal cord injury.

Traumatic injury to the central nervous system (CNS) is further complicated by an increase in secondary neuronal damage imposed by activated microglia/macrophages. MicroRNA-124 (miR-124) is responsible for mouse monocyte quiescence and reduction of their inflammatory cytokine production. We describe the formulation and ex vivo transfection of chitosan/miR-124 polyplex particles into rat microglia and the resulting reduction of reactive oxygen species (ROS) and TNF-α and lower expression of MHC-II. Upon microinjection into uninjured rat spinal cords, particles formed with Cy3-labeled control sequence RNA, were specifically internalized by OX42 positive macrophages and microglia cells. Alternatively particles injected in the peritoneum were transported by macrophages to the site of spinal cord injury 72 h post injection. Microinjections of chitosan/miR-124 particles significantly reduced the number of ED-1 positive macrophages in the injured spinal cord. Taken together, these data present a potential treatment technique to reduce inflammation for a multitude of CNS neurodegenerative conditions. FROM THE CLINICAL EDITOR: The treatment of spinal cord injury remains an unresolved problem. Secondary damage is often the result of inflammation caused by activated microglia and/or macrophages. In this article, the authors developed their formulation of chitosan/miR-124 polyplex particles and investigated their use in the suppression of neuronal inflammation. This exciting data may provide a new horizon for patients who suffer from spinal cord injury.

miR-124 disinhibits neurite outgrowth in an inflammatory environment.

Lesions of the central nervous system elicit inflammatory responses that counteract the regeneration of neurites. Microglia and infiltrating macrophages that were activated by trauma have been identified as cellular sources of inhibitory factors. We examine cultured macrophage (RAW264.7) and neuronal (PC12) cell lines to ascertain the potential modulators of the inflammatory impact on neurons. By exposing quiescent macrophages to lipopolysaccharide (LPS) and interferon γ (IFN-γ), cells can be transformed into an activated M1 phenotype. Neurite extension was induced in PC12 cells by culturing them in the presence of nerve growth factor. Neurite outgrowth was quantified by analyzing immunofluorescence and phase contrast microscopy images. Activated macrophages significantly reduced neurite extension. Macrophage activation by LPS/IFN-γ induced a 1000-fold increase in tumor necrosis factor alpha (TNF-α) secretion, as quantified by enzyme-linked immunosorbent assays (ELISA). Recombinant TNF-α inhibited neurite formation at concentrations as low as 0.016 ng/ml. In contrast, the masking of TNF-α with specific functional antibodies abrogated neurite growth inhibition by activated macrophages. Taken together, these results indicated that TNF-α is a key component of inhibitory macrophage action. The transfection of PC12 neurons with microRNA-124 (miR-124) counteracted the inhibition of neurites mediated by both recombinant TNF-α and macrophages. miR-124 did not stimulate neurite formation per se, nor was cell viability affected. These data suggest that miR-124 might be a valuable tool for desensitizing neurons to a repulsive inflammatory environment.

FGF-23 regulates CYP27B1 transcription in the kidney and in extra-renal tissues.

The mitochondrial enzyme 25-hydroxyvitamin D 1α-hydroxylase, which is encoded by the CYP27B1 gene, converts 25OHD to the biological active form of vitamin D, 1,25-dihydroxyvitamin D (1,25(OH)2D). Renal 1α-hydroxylase activity is the principal determinant of the circulating 1,25(OH)2D concentration and enzyme activity is tightly regulated by several factors. Fibroblast growth factor-23 (FGF-23) decreases serum 1,25(OH)2D concentrations by suppressing CYP27B1 mRNA abundance in mice. In extra-renal tissues, 1α-hydroxylase is responsible for local 1,25(OH)2D synthesis, which has important paracrine actions, but whether FGF-23 regulates CYP27B1 gene expression in extra-renal tissues is unknown. We sought to determine whether FGF-23 regulates CYP27B1 transcription in the kidney and whether extra-renal tissues are target sites for FGF-23-induced suppression of CYP27B1. In HEK293 cells transfected with the human CYP27B1 promoter, FGF-23 suppressed promoter activity by 70%, and the suppressive effect was blocked by CI-1040, a specific inhibitor of extracellular signal regulated kinase 1/2. To examine CYP27B1 transcriptional activity in vivo, we crossed fgf-23 null mice with mice bearing the CYP27B1 promoter-driven luciferase transgene (1α-Luc). In the kidney of FGF-23 null/1α-Luc mice, CYP27B1 promoter activity was increased by 3-fold compared to that in wild-type/1α-Luc mice. Intraperitoneal injection of FGF-23 suppressed renal CYP27B1 promoter activity and protein expression by 26% and 60% respectively, and the suppressive effect was blocked by PD0325901, an ERK1/2 inhibitor. These findings provide evidence that FGF-23 suppresses CYP27B1 transcription in the kidney. Furthermore, we demonstrate that in FGF-23 null/1α-Luc mice, CYP27B1 promoter activity and mRNA abundance are increased in several extra-renal sites. In the heart of FGF-23 null/1α-Luc mice, CYP27B1 promoter activity and mRNA were 2- and 5-fold higher, respectively, than in control mice. We also observed a 3- to 10-fold increase in CYP27B1 mRNA abundance in the lung, spleen, aorta and testis of FGF-23 null/1α-Luc mice. Thus, we have identified novel extra-renal target sites for FGF-23-mediated regulation of CYP27B1.

Purulent pericarditis due to co-infection with Streptococcus pneumoniae and Mycobacterium tuberculosis in a patient with features of advanced HIV infection.

BACKGROUND: Both Mycobacterium tuberculosis and Streptococcus pneumoniae are common pathogens in patients with HIV infection. CASE PRESENTATION: We present an unusual case of purulent pericarditis resulting in cardiac tamponade due to infection with both organisms. We highlight the re-emergence of pneumococcal pericarditis in the HIV era and describe the pitfalls and challenges in the diagnosis of this condition. CONCLUSION: Clinicians working in HIV endemic areas need to consider dual infection with these organisms in patients who respond inadequately to either antibiotics or anti-tuberculous therapy alone.