Engineered AAVs for non-invasive gene delivery to rodent and non-human primate nervous systems.

Gene therapy offers great promise in addressing neuropathologies associated with the central and peripheral nervous systems (CNS and PNS). However, genetic access remains difficult, reflecting the critical need for the development of effective and non-invasive gene delivery vectors across species. To that end, we evolved adeno-associated virus serotype 9 (AAV9) capsid in mice and validated two capsids, AAV-MaCPNS1 and AAV-MaCPNS2, across rodent species (mice and rats) and non-human primate (NHP) species (marmosets and rhesus macaques). Intravenous administration of either AAV efficiently transduced the PNS in rodents and both the PNS and CNS in NHPs. Furthermore, we used AAV-MaCPNS1 in mice to systemically deliver the following: (1) the neuronal sensor jGCaMP8s to record calcium signal dynamics in nodose ganglia and (2) the neuronal actuator DREADD to dorsal root ganglia to mediate pain. This conclusively demonstrates the translatability of these two systemic AAVs across four species and their functional utility through proof-of-concept studies in mice.

Sensory representation and detection mechanisms of gut osmolality change.

Ingested food and water stimulate sensory systems in the oropharyngeal and gastrointestinal areas before absorption1,2. These sensory signals modulate brain appetite circuits in a feed-forward manner3-5. Emerging evidence suggests that osmolality sensing in the gut rapidly inhibits thirst neurons upon water intake. Nevertheless, it remains unclear how peripheral sensory neurons detect visceral osmolality changes, and how they modulate thirst. Here we use optical and electrical recording combined with genetic approaches to visualize osmolality responses from sensory ganglion neurons. Gut hypotonic stimuli activate a dedicated vagal population distinct from mechanical-, hypertonic- or nutrient-sensitive neurons. We demonstrate that hypotonic responses are mediated by vagal afferents innervating the hepatic portal area (HPA), through which most water and nutrients are absorbed. Eliminating sensory inputs from this area selectively abolished hypotonic but not mechanical responses in vagal neurons. Recording from forebrain thirst neurons and behavioural analyses show that HPA-derived osmolality signals are required for feed-forward thirst satiation and drinking termination. Notably, HPA-innervating vagal afferents do not sense osmolality itself. Instead, these responses are mediated partly by vasoactive intestinal peptide secreted after water ingestion. Together, our results reveal visceral hypoosmolality as an important vagal sensory modality, and that intestinal osmolality change is translated into hormonal signals to regulate thirst circuit activity through the HPA pathway.

Expression of leukotriene B4 receptor 1 defines functionally distinct DCs that control allergic skin inflammation.

Leukotriene B4 (LTB4) receptor 1 (BLT1) is a chemotactic G protein-coupled receptor expressed by leukocytes, such as granulocytes, macrophages, and activated T cells. Although there is growing evidence that BLT1 plays crucial roles in immune responses, its role in dendritic cells remains largely unknown. Here, we identified novel DC subsets defined by the expression of BLT1, namely, BLT1hi and BLT1lo DCs. We also found that BLT1hi and BLT1lo DCs differentially migrated toward LTB4 and CCL21, a lymph node-homing chemoattractant, respectively. By generating LTB4-producing enzyme LTA4H knockout mice and CD11c promoter-driven Cre recombinase-expressing BLT1 conditional knockout (BLT1 cKO) mice, we showed that the migration of BLT1hi DCs exacerbated allergic contact dermatitis. Comprehensive transcriptome analysis revealed that BLT1hi DCs preferentially induced Th1 differentiation by upregulating IL-12p35 expression, whereas BLT1lo DCs accelerated T cell proliferation by producing IL-2. Collectively, the data reveal an unexpected role for BLT1 as a novel DC subset marker and provide novel insights into the role of the LTB4-BLT1 axis in the spatiotemporal regulation of distinct DC subsets.

Neural populations for maintaining body fluid balance.

Fine balance between loss-of water and gain-of water is essential for maintaining body fluid homeostasis. The development of neural manipulation and mapping tools has opened up new avenues to dissect the neural circuits underlying body fluid regulation. Recent studies have identified several nodes in the brain that positively and negatively regulate thirst. The next step forward would be to elucidate how neural populations interact with each other to control drinking behavior.

Stepwise phosphorylation of leukotriene B4 receptor 1 defines cellular responses to leukotriene B4.

Leukotriene B4 (LTB4) receptor type 1 (BLT1) is abundant in phagocytic and immune cells and plays crucial roles in various inflammatory diseases. BLT1 is phosphorylated at several serine and threonine residues upon stimulation with the inflammatory lipid LTB4 Using Phos-tag gel electrophoresis to separate differentially phosphorylated forms of BLT1, we identified two distinct types of phosphorylation, basal and ligand-induced, in the carboxyl terminus of human BLT1. In the absence of LTB4, the basal phosphorylation sites were modified to various degrees, giving rise to many different phosphorylated forms of BLT1. Different concentrations of LTB4 induced distinct phosphorylation events, and these ligand-induced modifications facilitated additional phosphorylation events at the basal phosphorylation sites. Because neutrophils migrate toward inflammatory sites along a gradient of LTB4, the degree of BLT1 phosphorylation likely increases in parallel with the increase in LTB4 concentration as the cells migrate. At high concentrations of LTB4, deficiencies in these two types of phosphorylation events impaired chemotaxis and ß-hexosaminidase release, a proxy for degranulation, in Chinese hamster ovary (CHO-K1) and rat basophilic leukemia (RBL-2H3) cells, respectively. These results suggest that an LTB4 gradient around inflammatory sites enhances BLT1 phosphorylation in a stepwise manner to facilitate the precise migration of phagocytic and immune cells and the initiation of local responses, including degranulation.

Receptor for Advanced Glycation End Products Regulates Leukotriene B4 Receptor 1 Signaling.

Leukotriene B4 receptor 1 (BLT1), a high-affinity G protein-coupled receptor (GPCR) for leukotriene B4 (LTB4), plays important roles in inflammatory and immune reactions. Although the LTB4-BLT1 axis is known to promote inflammation, the binding proteins that modulate LTB4-BLT1 signaling have not been identified. Recently, we discovered that receptor for advanced glycation end products (RAGE) interacts with BLT1 and modulates LTB4-BLT1 signaling. We propose RAGE as a new class of GPCR modulator and a new target of future GPCR studies.

Modulation of leukotriene B4 receptor 1 signaling by receptor for advanced glycation end products (RAGE).

Leukotriene B4 (LTB4) receptor 1 (BLT1), a high-affinity GPCR for LTB4, plays important roles in acute and chronic inflammatory diseases. Although the LTB4-BLT1 axis is known to promote inflammation, no studies have defined the binding proteins that modulate LTB4-BLT1 signaling. In this study, the receptor for advanced glycation end products (RAGE) interacted with BLT1 in human cervical epithelial HeLa cells. RAGE increased LTB4-BLT1-dependent ERK phosphorylation and inhibited LTB4-BLT1-dependent activation of NF-κB and up-regulation of proinflammatory cytokines and chemokines. RAGE-dependent inhibition of NF-κB was blunted by treatment with an MEK inhibitor, suggesting that RAGE suppresses LTB4-BLT1-dependent NF-κB signaling by enhancing the MEK-ERK pathway. Meanwhile, in a chemotaxis assay of mouse bone marrow-derived neutrophils, the velocity of LTB4-dependent neutrophil migration was attenuated by soluble RAGE, which is an inhibitory decoy protein for RAGE signaling, in a dose-dependent manner (0.2-5 µg/ml), or by RAGE deficiency. Furthermore, both LTB4-dependent ERK phosphorylation in neutrophils and LTB4-dependent neutrophil accumulation in a murine peritonitis model were significantly attenuated in RAGE-deficient mice compared with C57BL/6J wild-type mice, indicating that RAGE potentiates LTB4-dependent neutrophil migration by enhancing ERK phosphorylation. Our results demonstrate that RAGE interacts with BLT1 and modulates LTB4-BLT1 signaling through potentiation of the MEK-ERK pathway.-Ichiki, T., Koga, T., Okuno, T., Saeki K., Yamamoto, Y., Yamamoto, H., Sakaguchi, M., Yokomizo, T. Modulation of leukotriene B4 receptor 1 signaling by receptor for advanced glycation end products (RAGE).

Neurokinin B activates the formation and bone resorption activity of rat osteoclasts.

Neurokinin B (NKB) is a neuropeptide in the tachykinin family that acts as a neurotransmitter and neuromodulator, primarily in the central nervous system. The distribution and role of NKB and its receptor, the neurokinin-3 receptor (NK-3R), in peripheral tissues are poorly understood. In this study, we investigated the distribution of NKB and NK-3R in peripheral tissues as well as the role of NKB in bone metabolism, especially in osteoclast formation and bone resorption activity through NK-3R. The distributions of NKB in intact rat neurons of the trigeminal ganglion (TG) and in axons of periodontal tissue were investigated by immunohistochemistry. Osteoclasts from cultured rat bone marrow cells were used to examine the distribution of NK-3R by immunocytochemistry and RT-PCR and to investigate the effects of NKB on the resorption activity of osteoclasts on ivory slices. We found that NKB immunopositive neurons were localized in the rat TG and that NKB immunopositive axons were distributed in periodontal tissues. Immunoreactivity for NK-3R was found in cultured osteoclasts, and NK-3R mRNA expression in the osteoclasts was confirmed by RT-PCR. The addition of NKB significantly increased the number of osteoclasts and the resorption area compared with the control. These findings suggest that NKB was localized in peripheral neurons and may involve the activation of osteoclast formation and bone resorption through NK-3R.