Fatty acid preference for beta-oxidation in mitochondria of murine cultured astrocytes.

The brain utilizes glucose as a primary energy substrate but also fatty acids for the ß-oxidation in mitochondria. The ß-oxidation is reported to occur mainly in astrocytes, but its capacity and efficacy against different fatty acids remain unknown. Here, we show the fatty acid preference for the ß-oxidation in mitochondria of murine cultured astrocytes. Fatty acid oxidation assay using an extracellular flux analyzer showed that saturated or monosaturated fatty acids, palmitic acid and oleic acid, are preferred substrates over polyunsaturated fatty acids like arachidonic acid and docosahexaenoic acid. We also report that fatty acid binding proteins expressed in the astrocytes contribute less to fatty acid transport to mitochondria for ß-oxidation. Our results could give insight into understanding energy metabolism through fatty acid consumption in the brain.

Genetics of bipolar disorder: insights into its complex architecture and biology from common and rare variants.

Bipolar disorder (BD) is a common mental disorder characterized by recurrent mood episodes, which causes major socioeconomic burdens globally. Though its disease pathogenesis is largely unknown, the high heritability of BD indicates strong contributions from genetic factors. In this review, we summarize the recent achievements in the genetics of BD, particularly those from genome-wide association study (GWAS) of common variants and next-generation sequencing analysis of rare variants. These include the identification of dozens of robust disease-associated loci, deepening of our understanding of the biology of BD, objective description of correlations with other psychiatric disorders and behavioral traits, formulation of methods for predicting disease risk and drug response, and the discovery of a single gene associated with bipolar disorder and schizophrenia spectrum with a large effect size. On the other hand, the findings to date have not yet made a clear contribution to the improvement of clinical psychiatry of BD. We overview the remaining challenges as well as possible paths to resolve them, referring to studies of other major neuropsychiatric disorders.

Integrin expression and extracellular matrix adhesion of septoclasts, pericytes, and endothelial cells at the chondro-osseous junction and the metaphysis of the proximal tibia in young mice.

We previously reported that septoclasts, which are uncalcified growth plate (GP) cartilage matrix-resorbing cells, are derived from pericytes surrounding capillary endothelial cells. Resorption of the GP is assumed to be regulated synchronously by septoclasts, pericytes, and endothelial cells. To reveal the contribution of the extracellular matrix (ECM) to the regulatory mechanisms of septoclastic cartilage resorption, we investigated the spatial correlation between the cells and the ECM in the GP matrix and basement membrane (BM) and investigated the expression of integrins-ECM receptors-in the cells. Septoclasts attached to the transverse septa containing collagen-II/-X at the tip of their processes and to the longitudinal septa containing collagen-II/-X at the spine-like processes extending from their bodies and processes. Collagen-IV and laminin α4 in the BM were sparsely detected between septoclasts and capillary endothelial cells at the chondro-osseous junction (COJ) and were absent in the outer surface of pericytes at the metaphysis. Integrin α1/α2, integrin α1, and integrin α2/α6 were detected in the cell membranes of septoclasts, pericytes, and endothelial cells, respectively. These results suggest that the adhesion between septoclasts and the cartilage ECM forming the scaffolds for cartilage resorption and migration is provided by integrin α2-collagen-II/-X interaction and that the adhesions between the BM and pericytes or endothelial cells are mediated by integrin α1-collagen-IV and integrin α2/α6-laminin interaction, respectively.

Effects of Ndufs4 Deletion on Hearing after Various Acoustic Exposures.

Mitochondrial dysfunction can cause cochlear dysfunction and accelerate noise-induced hearing loss (NIHL). NADH dehydrogenase (ubiquinone) Fe-S protein 4 (Ndufs4) is one of the subunits of mitochondrial complex I and has a role in the assembly and stabilization of complex I. However, the involvement of Ndufs4 in the pathogenesis of NIHL has not been reported. The aim of this study was to evaluate whether Ndufs4 deletion causes vulnerability to noise exposures. The wild-type (WT) and Ndufs4 knockout (KO) mice with C57BL/6J genetic background were used. Cochlear histology and hearing thresholds were assessed after noise exposure at 100 or 86 dB sound pressure level (SPL). Immunostaining showed the widespread expression of Ndufs4 in the cochlea. After noise exposure at 100 dB SPL, auditory brainstem response (ABR) threshold shifts at 4 kHz in Ndufs4 KO mice were significantly higher than that in WT mice. After noise exposure at 86 dB SPL, ABR threshold shifts, wave 1 amplitudes, and the number of synapses in the inner hair cells were not significantly different. RNA sequencing revealed the decreased expression of energy generation-related genes inNdufs4 KO mice. Ndufs4 deficiency accelerates permanent low-frequency threshold shifts after moderate noise exposure.

Fatty acid-binding protein 5 limits the generation of Foxp3+ regulatory T cells through regulating plasmacytoid dendritic cell function in the tumor microenvironment.

Plasmacytoid dendritic cells (pDCs) promote viral elimination by producing large amounts of Type I interferon. Recent studies have shown that pDCs regulate the pathogenesis of diverse inflammatory diseases, such as cancer. Fatty acid-binding protein 5 (FABP5) is a cellular chaperone of long-chain fatty acids that induce biological responses. Although the effects of FABP-mediated lipid metabolism are well studied in various immune cells, its role in pDCs remains unclear. This study, which compares wild-type and Fabp5-/- mice, provides the first evidence that FABP5-mediated lipid metabolism regulates the commitment of pDCs to inflammatory vs tolerogenic gene expression patterns in the tumor microenvironment and in response to toll-like receptor stimulation. Additionally, we demonstrated that FABP5 deficiency in pDCs affects the surrounding cellular environment, and that FABP5 expression in pDCs supports the appropriate generation of regulatory T cells (Tregs). Collectively, our findings reveal that pDC FABP5 acts as an important regulator of tumor immunity by controlling lipid metabolism.

Spatial and chronological localization of septoclasts in the mouse Meckel's cartilage.

Meckel's cartilage (MC) in the first branchial arch of mammals is a transient structure that disappears before birth, except for the most anterior and posterior portions. Recent studies reported that some congenital abnormalities in craniofacial regions are linked with the persistence or dysplasia of MC. However, the mechanisms underlying the resorption of MC have not been elucidated. Cartilage resorption in endochondral ossification is performed by multinuclear osteoclasts/chondroclasts as well as mononuclear septoclasts, which were newly added to the list of cartilage phagocytes. Septoclasts located exclusively at the chondro-osseous junction of the growth plate resorb the uncalcified cartilage matrix. We hypothesized that septoclasts participate in the resorption of MC and attempted to clarify the localization and roles of septoclasts in MC of mouse using a specific immunohistochemistry marker, epidermal type-fatty acid-binding protein (E-FABP/FABP5). E-FABP-immunopositive septoclasts were detected for the first time at the beginning of MC resorption and localized along the resorption surface. Septoclasts of MC in embryonic mice possessed several processes that elongated toward the uncalcified cartilage matrix, expressed cathepsin B, and exhibited characteristic pericapillary localization. Additionally, they localized between hypertrophied cartilage and osteoclasts/chondroclasts in the resorption surface. Confocal laser-scanning microscopy revealed a decrease in the numbers of septoclasts and their processes with the progression of MC disappearance before birth. The present study showed that E-FABP-immunopositive septoclasts participated in the disappearance of MC through the resorption of the uncalcified cartilage matrix and that they have different roles from osteoclasts/chondroclasts.

Functional Analysis of the Transcriptional Regulator IκB-ζ in Intestinal Homeostasis.

BACKGROUND: The Toll-like receptor signaling pathway contributes to the regulation of intestinal homeostasis through interactions with commensal bacteria. Although the transcriptional regulator IκB-ζ can be induced by Toll-like receptor signaling, its role in intestinal homeostasis is still unclear. AIMS: To investigate the role of IκB-ζ in gut homeostasis. METHODS: DSS-administration induced colitis in control and IκB-ζ-deficient mice. The level of immunoglobulins in feces was detected by ELISA. The immunological population in lamina propria (LP) was analyzed by FACS. RESULTS: IκB-ζ-deficient mice showed severe inflammatory diseases with DSS administration in the gut. The level of IgM in the feces after DSS administration was less in IκB-ζ-deficient mice compared to control mice. Upon administration of DSS, IκB-ζ-deficient mice showed exaggerated intestinal inflammation (more IFN-g-producing CD4+ T cells in LP), and antibiotic treatment canceled this inflammatory phenotype. CONCLUSION: IκB-ζ plays a crucial role in maintaining homeostasis in the gut.

Curcumin analog GO-Y030 boosts the efficacy of anti-PD-1 cancer immunotherapy.

Regulatory T cells (Tregs) in the tumor microenvironment regulate tumor immunity. Programmed cell death protein 1 (PD-1) is known to be expressed on Tregs and plays crucial roles in suppressing tumor immunity. However, the immune checkpoint inhibitor, anti-PD-1 antibody, is known to promote the proliferation of the Treg population in tumor-infiltrating lymphocytes, thereby restricting the efficacy of cancer immunotherapy. In this study, we focused on the curcumin analog GO-Y030, an antitumor chemical. GO-Y030 inhibited the immune-suppressive ability of Tregs via metabolic changes in vitro, even in the presence of immune checkpoint inhibitors. Mechanistically, GO-Y030 inhibited the mTOR-S6 axis in Tregs, which plays a pivotal role in their immune-suppressive ability. GO-Y030 also controlled the metabolism in cultured CD4+ T cells in the presence of TGF-ß + IL-6; however, it did not prevent Th17 differentiation. Notably, GO-Y030 significantly inhibited IL-10 production from Th17 cells. In the tumor microenvironment, L-lactate produced by tumors is known to support the suppressive ability of Tregs, and GO-Y030 treatment inhibited L-lactate production via metabolic changes. In addition, experiments in the B16-F10 melanoma mouse model revealed that GO-Y030 helped inhibit the anti-PD-1 immune checkpoint and reduce the Treg population in tumor-infiltrating lymphocytes. Thus, GO-Y030 controls the metabolism of both Tregs and tumors and could serve as a booster for anti-immune checkpoint inhibitors.

Expression and enhancement of FABP4 in septoclasts of the growth plate in FABP5-deficient mouse tibiae.

In our previous study, fatty acid-binding protein 5 (FABP5) was expressed in septoclasts with long processes which are considered to resorb uncalcified matrix of the growth plate (GP) cartilage, and no apparent abnormalities were detected in the histo-architecture of the GP of FABP5-deficient (FABP5-/-) mice. Those finding lead us to hypothesize that another FABP can compensate the deletion of FABP5 in septoclasts of its gene-mutant mice. Based on the hypothesis, the present study examined the expression levels of several other FABPs in septoclasts and their morphology in FABP5-/- mouse tibiae. Processes of FABP5-/- septoclasts tend to be shorter than wild septoclasts. FABP4-positive septoclasts in FABP5-/- mice were more numerous than those cells in wild mice.Peroxisome proliferator-activated receptor (PPAR) γ was expressed in FABP4-positive septoclasts of FABP5-/- mice as well as mice administered with GW1929, a PPARγ agonist, suggesting that the occurrence of PPARγ induces an increase of FABP4-positive septoclasts. The present finding suggests that the functional exertion of FABP5 in septoclasts is supplemented by FABP4 in normal and FABP5-/- mice, and that the expression of FABP4 is up-regulated in accompany with PPARγ in FABP5-/- for maintenance of resorptive activity in the GP.

Fatty acid-binding protein 3 controls contact hypersensitivity through regulating skin dermal Vγ4+ γ/δ T cell in a murine model.

BACKGROUND: Fatty acid-binding protein 3 (FABP3) is a cytosolic carrier protein of polyunsaturated fatty acids (PUFAs) and regulates cellular metabolism. However, the physiological functions of FABP3 in immune cells and how FABP3 regulates inflammatory responses remain unclear. METHODS: Contact hypersensitivity (CHS) induced by 2,4-dinitrofluorobenzene (DNFB) and fluorescein isothiocyanate was applied to the skin wild-type and Fabp3-/- mice. Skin inflammation was assessed using FACS, histological, and qPCR analyses. The development of γ/δ T cells was evaluated by a co-culture system with OP9/Dll1 cells in the presence or absence of transgene of FABP3. RESULTS: Fabp3-deficient mice exhibit a more severe phenotype of contact hypersensitivity (CHS) accompanied by infiltration of IL-17-producing Vγ4+ γ/δ T cells that critically control skin inflammation. In Fabp3-/- mice, we found a larger proportion of Vγ4+ γ/δ T cells in the skin, even though the percentage of total γ/δ T cells did not change at steady state. Similarly, juvenile Fabp3-/- mice also contained a higher amount of Vγ4+ γ/δ T cells not only in the skin but in the thymus when compared with wild-type mice. Furthermore, thymic double-negative (DN) cells expressed FABP3, and FABP3 negatively regulates the development of Vγ4+ γ/δ T cells in the thymus. CONCLUSIONS: These findings suggest that FABP3 functions as a negative regulator of skin inflammation through limiting pathogenic Vγ4+ γ/δ T-cell generation in the thymus.