Fatty Acid-Binding Protein 4 Inhibition Promotes Locomotor and Autonomic Recovery in Rats following Spinal Cord Injury.

The inflammatory response associated with traumatic spinal cord injury (SCI) contributes to locomotor and sensory impairments. Pro-inflammatory (M1) macrophages/microglia (MϕMG) are the major cellular players in this response as they promote chronic inflammation resulting in injury expansion and tissue damage. Fatty acid-binding protein 4 (FABP4) promotes M1 MϕMG differentiation; however, it is unknown if FABP4 also plays a role in the etiology of SCI. The present study investigates whether FABP4's gene expression influences functional recovery following SCI. Analysis of quantitative polymerase chain reaction data shows a robust induction of FABP4 messenger RNA (mRNA; >100 fold) in rats subjected to a T9-T10 contusion injury compared with control. Western blot experiments reveal significant upregulation of FABP4 protein at the injury epicenter, and immunofluorescence analysis identifies that this upregulation occurs in CD11b+ MϕMG. Further, upregulation of FABP4 gene expression correlates with peroxisome proliferator-activated receptor γ (PPARγ) downregulation, inactivation of Iκßα, and the activation of the NF-κB pathway. Analysis of locomotor recovery using the Basso-Beattie-Bresnahan's locomotor scale and the CatWalk gait analysis system shows that injured rats treated with FABP4 inhibitor BMS309403 have significant improvements in locomotion compared with vehicle controls. Additionally, inhibitor-treated rats exhibit enhanced autonomic bladder reflex recovery. Immunofluorescence experiments also show the administration of the FABP4 inhibitor increases the number of CD163+ and liver arginase+ M2 MϕMG within the epicenter and penumbra of the injured spinal cord 28 days post-injury. These findings show that FABP4 may significantly exacerbate locomotor and sensory impairments during SCI by modulating macrophage/microglial activity.

Natural Killer Cell Phenotype and Functionality Affected by Exposure to Extracellular Survivin and Lymphoma-Derived Exosomes.

The inherent abilities of natural killer (NK) cells to recognize and kill target cells place them among the first cells with the ability to recognize and destroy infected or transformed cells. Cancer cells, however, have mechanisms by which they can inhibit the surveillance and cytotoxic abilities of NK cells with one believed mechanism for this: their ability to release exosomes. Exosomes are vesicles that are found in abundance in the tumor microenvironment that can modulate intercellular communication and thus enhance tumor malignancy. Recently, our lab has found cancer cell exosomes to contain the inhibitor of apoptosis (IAP) protein survivin to be associated with decreased immune response in lymphocytes and cellular death. The purpose of this study was to explore the effect of survivin and lymphoma-derived survivin-containing exosomes on the immune functions of NK cells. NK cells were obtained from the peripheral blood of healthy donors and treated with pure survivin protein or exosomes from two lymphoma cell lines, DLCL2 and FSCCL. RNA was isolated from NK cell samples for measurement by PCR, and intracellular flow cytometry was used to determine protein expression. Degranulation capacity, cytotoxicity, and natural killer group 2D receptor (NKG2D) levels were also assessed. Lymphoma exosomes were examined for size and protein content. This study established that these lymphoma exosomes contained survivin and FasL but were negative for MHC class I-related chains (MIC)/B (MICA/B) and TGF-ß. Treatment with exosomes did not significantly alter NK cell functionality, but extracellular survivin was seen to decrease natural killer group 2D receptor (NKG2D) levels and the intracellular protein levels of perforin, granzyme B, TNF-α, and IFN-γ.