Psychological and social stresses are known to be risk factors for psychiatric disorders, including depression and anxiety. On the other hand, exposure to these stresses can also cause prolonged and severe pain. However, the pathological mechanism for stress-induced chronic pain is complex, and there are many unresolved aspects, and no effective therapeutic drugs have been established. Since the discovery of the long-chain fatty acid receptor GPR40/FFAR1 about 20 years ago, research on the mechanism that promotes insulin secretion in the pancreas has progressed. Previously, we have worked to elucidate the physiological effects of GPR40/FFAR1 in the central nervous system and has found that it is involved in the regulation of pain and emotion. Based on these findings, they are now investigating the involvement of fatty acid receptors signaling in the development of stress-related chronic pain. In this review, we discuss the status of psychological stress-related chronic pain and the GPR40/FFAR1-mediated and -striking regulatory mechanisms of stress-induced chronic pain, based on our findings using a mouse model of chronic pain created by loading postoperative pain to a social defeat stress model mouse that mimics psychosocial stress. We summarized about the involvement of fatty acid receptor signaling as a new therapeutic candidate for chronic pain in this review.

Fibromyalgia (FM) is characterized by chronic generalized pain accompanied by various symptoms, such as extreme fatigue, insomnia and depression. Clinical studies have indicated the presence of psychological stress, sympathetic nervous system hyperexcitation and immune system abnormalities, as a trigger for the onset of the disease, but the contribution to the pathogenesis of the disease remains unclear. Here, we employed the repeated acid saline-induced generalized pain (AcGP) model, as an experimental mouse model of FM. In this model, the unilateral repeated acid injection into gastrocnemius muscle induced transient and long-lasting mechanical hypersensitivity. We focused on the spleen, a secondary lymphoid organ, and found that the intravenous treatments of splenocytes derived from AcGP mice caused mechanical hypersensitivity in naїve mice. Since the spleen is directly innervated by sympathetic nerve, we examined whether adrenergic receptors are necessary for pain development or maintenance. The administration of butoxamine, a selective β₂-blocker, prevented the development but did not reverse the maintenance of pain-like behavior in AcGP mice. Furthermore, β₂-blockade in donor AcGP mice eliminated pain reproduction in recipient mice injected with AcGP splenocytes. We currently employed another model of FM, the intermittent psychological stress-induced generalized pain (IPGP) model and found that as in AcGP model, the sympathetic nervous system and the spleen play important roles. These results suggest that sympathetic β₂ signaling is enhanced by physical/psychological stress, and that immune system cells in the spleen activated in response play an important role in the formation and maintenance of chronic pain.

Spinal cord astrocytes are activated in chronic pain models, especially under conditions of prolonged pain. Hence, targeting spinal cord astrocytes for the development of useful analgesics has attracted much attention. In the CNS, connexin43 (Cx43), a membrane protein expressed and functioning exclusively in astrocytes, is well known to be involved in intercellular signaling as a component of gap junction, but also interacts with intracellular molecules via its characteristically long C-terminal region, thereby affecting cellular function. Previously, we found that Cx43 expression was markedly reduced in spinal dorsal horn astrocytes from a mouse model of neuropathic pain. In order to investigate the relationship between reduced Cx43 expression in spinal astrocytes and the onset of pain, we showed that reduced Cx43 expression altered the expression of pain-related molecules such as the glutamate transporter GLT-1 and the pro-inflammatory cytokine interleukin-6 (IL-6). In particular, we focused on the regulation of IL-6 expression by reduced Cx43 expression in both in vivo and in vitro analyses, and found that IL-6 expression is increased through the Akt- glycogen synthase kinase-3β (GSK-3β) signaling system driven by reduced Cx43 expression during neuropathic pain, which in turn triggers pain. These findings suggest that astrocyte Cx43 is involved in pain prolongation by regulating gene expression of nociceptive factors through interactions with intracellular signaling molecules, which is different from its previously known function, and thus raises expectations for its potential as a new drug target for chronic pain.

Endometriosis is a chronic, progressive inflammatory disease that occurs in approximately 10% of women of reproductive age, resulting in a decreased quality of life due to dysmenorrhea, chronic pain, and other problems. The primary treatment is pain control and fertility preservation, and while preserving ovarian function through drug therapy and surgery, assisted reproductive technology (ART), including in vitro fertilization (IVF), is also utilized. Hormonal therapies such as low-dose estrogen/progestin (LEP), progestins, and GnRH analogs are often the drug of choice. We presented that IAP (inhibitor of apoptotic protein) inhibitors can potentially be novel agents for treating endometriosis. Our studies using cultured cells derived from human endometriotic lesions and mouse models have revealed that inflammatory cytokines and antiapoptotic factors (IAPs) produced by peritoneal macrophages or endometriosis cells are crucial and that NF-κB (nuclear factor-kappa B) plays a central role in the pathogenesis of endometriosis. The high expression of IAPs in human endometriotic tissues, its facilitative role in ectopic survival, and the effect of IAPs on drug-resistant apoptosis of human endometriotic cells indicate its potential as a novel drug for IAP inhibitors. We found that the medicinal herb parthenolide and selective estrogen receptor modulators (SERM) can reduce lesions through NF-κB inhibition. Recently, new findings were obtained by non-invasive observation of early lesions using bioluminescence technology and by applying knockout mouse models. We will show the possibility of new therapeutic agents for endometriosis.

The mainstay of treatment for endometriosis is hormonal therapy, which suppresses ovulation; therefore, patients cannot conceive during treatment. There is a dilemma with ovarian-sparing surgery, known as laparoscopic cystectomy, as it can potentially damage the ovaries. Therefore, there is a need for non-hormonal drug therapies. We addressed these challenges in endometriosis treatment, aiming to maintain ovarian function while achieving effective treatment through basic research. Herein, we present two studies using different mouse models of endometriosis. The first study investigates the effects of a nucleotide-binding oligomerization domain, leucine-rich repeat, and pyrin domain-containing (NLRP) 3 inhibitor in a mouse model of ovarian endometriotic cysts. We confirmed the increased expression of NLRP in ovarian endometriotic cysts compared with that in the uterine endometrium in both patient-derived samples and mouse model lesions. Administering an NLRP3 inhibitor to model mice resulted in lesion reduction. The second study used a peritoneal lesion mouse model to examine bacterial infection in the endometrium and its association with endometriosis development. Using existing databases and patient-derived samples, we identified that Fusobacterium was involved in the development of endometriosis and lesion enlargement when infecting the endometrium in the model. Furthermore, antibiotic treatment led to a reduction in the lesions. These studies highlight the potential of repositioning existing drugs with NLRP3 inhibitory effects or antibiotics as new non-hormonal treatments for endometriosis.

In endometriosis, the tissues similar to the endometrial tissue attaches outside the uterine cavity, causing inflammation and fibrosis. The retrograde menstruation theory is the most plausible mechanism, though the detailed pathogenesis remains unclear. Our observations suggest that endometriosis-like lesions occur more often at sites of ovarian excision causing bleeding in mouse models. Additionally, prostaglandin E2 (PGE2) and thrombin, a protease-activated receptor (PAR) agonist in menstrual blood exacerbate inflammation in these lesions. Focusing on the hypoxic conditions of menstrual blood, we investigated the effects of PGE2/thrombin on inflammation and fibrosis using primary cultured endometrial stromal cells (ESCs) and glandular epithelial cells (EECs) under low oxygen conditions. Chemokine CXCL12 secreted by endometrial stromal cells under hypoxia acts on CXCR4 receptors on glandular epithelial cells, inducing epithelial-mesenchymal transition (EMT), suggesting a possible role in endometriosis progression. RNA-seq analysis of PGE2/thrombin effects on endometrial stromal cells revealed activation of the transforming growth factor (TGF)-β pathway, particularly increased production and secretion of activin A, a member of the TGFβ family. Activin A, via increased connective tissue growth factor (CTGF) expression, promotes differentiation of endometrial stromal cells from fibroblast-like to myofibroblast transdifferentiation (FMT) of ESCs. In conclusion, targeting the CXCL12/CXCR4 and activin A/CTGF signaling pathways holds promise for improving fibrosis in endometriosis lesions.

Amyloid-β (Aβ) 42, one of the causes of Alzheimer’s disease (AD), is produced by the cleavage of amyloid precursor protein (APP) by β- or γ-secretases. Since Aβ42 oligomers exhibit strong neurotoxicity, Aβ42 is predicted to be a potentially efficient target for drug therapies. Recently, we screened peptides that activate MMP7 using our peptide library and found that the synthetic peptide JAL-TA9 (YKGSGFRMI), which is derived from the BoxA region of Tob1 protein, showed proteolytic activity. It is generally accepted that an enzyme should be a large molecular protein consisting of more than thousands of amino acids. Thus, this is the first finding that a small synthetic peptide has protease activity, and we termed Catalytide as the general name of peptides with protease activity. In this study, we demonstrate the cleavage activity of JAL-TA9 not only against the authentic soluble form of Aβ42 but also against the solid type of Aβ42 in the central region. In addition, we demonstrated the cleavage activity using brain slices of AD patients. JAL-TA9 decreased the amount of accumulated Aβ42 in the brain of Alzheimer’s patients. Taken together, JAL-TA9 is an attractive seed for the development of peptide drugs with a new strategy for Alzheimer’s disease.

Many studies have been conducted to find an effective drug for Alzheimer’s disease (AD) treatment. However, no effective drug applicable for clinical use has been developed. Recently, the FDA approved Lecanemab, an antibody drug that acts as an aggregation inhibitor against Amyloid-beta (Aβ), for AD treatment. However, there are still no fundamental drugs for AD. In this study, we present a strategy for AD treatment that removes Aβ by cleavage reaction using one of the Catalytides, JAL-TA9 (YKGSGFRMI). A single dose of JAL-TA9 administered into the CA1 region of the hippocampus and the intraventricular space improved the deficits in short-term memory of APP-knock-in mice. It also improved the memory of Aβ25-35-induced model mice, as evaluated by the Y-maze and objective recognition tests. These data strongly suggest that JAL-TA9 could be effective in treating AD. However, these administration methods are difficult to apply clinically due to their high invasiveness. Thus, we tested the improvement effects of dementia by administering JAL-TA9 nasally. It is very interesting and exciting that the dementia of Aβ25-35 induced AD model mice was improved by four applications once every three days. These results strongly suggest that JAL-TA9 is the best candidate for AD treatment because it is effective even in the late stage of AD.

We have reported on two Catalytides (Catalytic peptides), JAL-TA9 (YKGSGFRMI) and ANA-TA9 (SKGQAYRMI). Both peptides belong to the Tob/BTG family proteins and cleave Aβ42. Although Catalytides must be delivered to the brain parenchyma to treat Alzheimer’s disease, the blood-brain barrier (BBB) limits their entry into the brain from the systemic circulation. Thus, we evaluated the direct route of ANA-TA9 from the nasal cavity to the brain to bypass the BBB. In this study, we present our findings on JAL-TA9. Animal studies using rats and mice clarified that the plasma clearance of JAL-TA9 was more rapid than its in vitro degradation in plasma, whole blood, and cerebrospinal fluid (CSF). After nasal administration of JAL-TA9, brain concentrations were significantly higher than after intraperitoneal administration, despite much lower plasma concentration. This observation strongly suggests direct delivery of JAL-TA9 to the brain from the nasal cavity. Similar findings were observed for its transport to CSF after nasal and intravenous administration. The concentration of JAL-TA9 in the olfactory bulb peaked at 5 ‍min, while those in the frontal brain peaked at 30 ‍min and in the occipital brain at 60 ‍min. In conclusion, JAL-TA9 was efficiently delivered to the brain by nasal application compared to other routes.

Lecanemab is a new anti-amyloid antibody being developed as a treatment for Alzheimer’s disease. It is expected to delay the progression of the disease by reducing the accumulation of amyloid beta (Aβ) in the brain. However, no drug has been developed that can completely eliminate Aβ and improve symptoms. A representative Catalytide, JAL-TA9 (YKGSGFRMI), cleaves Aβ42 and improves symptoms in an Alzheimer’s disease mouse model, suggesting that JAL-TA9 is a promising candidate for treating Alzheimer’s disease by effectively eliminating Aβ. The catalytic center of JAL-TA9 is GSGFR. To identify better Catalytides for Alzheimer’s treatment, we analyzed the structure-activity relationship of 21 point-mutated GSGFR derivatives. In this process, we discovered two peptides, GSGFK and GSGNR, that not only inhibit Aβ25-35 aggregation but also dissolve aggregated Aβ25-35. Intracerebroventricular administration of GSGFK protected mice against Aβ25-35-induced short-term memory deficits and promoted microglial phagocytic activity. Like Lecanemab, GSGFK targets Aβ, but it has advantages such as safety, administration method, and cost. In this talk, we will discuss the potential of GSGFK as a therapeutic candidate for Alzheimer’s disease.

In drug discovery and pharmacological research, early identification of target molecules for compounds with pharmacological effects is crucial. However, this process often requires significant effort and can be rate-limiting, thereby slowing down research progress. This paper introduces a simplified and rapid method for quick screening of binding compounds or proteins. Utilizing Affinity Selection Mass Spectrometry (ASMS), this technique efficiently detects compound-target binding through size-exclusion chromatography and mass spectrometry. ASMS offers high sensitivity and specificity, making it ideal for accurate identification of binding interactions. We have further enhanced ASMS to handle membrane proteins without solubilization, creating Binder Selection Technology (BST). BST allows screening against both soluble and challenging membrane proteins such as GPCRs and SLC transporters. By using cell membrane fractions or organelle fractions with high target molecule expression, BST efficiently identifies potential binding compounds. This innovative method constructs a comprehensive database of binding compounds for various targets, facilitating rapid hypothesis testing and pharmacological evaluation. Additionally, BST screens 17,000 proteins, including membrane proteins, using wheat germ cell-free and animal cell expression systems. This approach allows exploration of binding interactions without labeling compounds or immobilizing proteins, preserving their native state. BST is powerful for identifying targets of compounds with known pharmacological effects but unknown targets in animal or cell-based assays. By utilizing BST, researchers can overcome bottlenecks in early drug discovery, significantly enhancing research speed and success rates. This method represents a major advancement, providing an efficient and effective way to identify and validate target molecules in drug discovery.

APOHIDE_® Lotion 20% is a topical agent for treating primary palmar hyperhidrosis that contains the active ingredient oxybutynin hydrochloride. Oxybutynin hydrochloride has anticholinergic effects and inhibits sweating by binding to the M₃ receptor, a subtype of the muscarinic acetylcholine receptor, in eccrine sweat glands. The clinical response to oxybutynin hydrochloride treatment also involves N-desethyloxybutynin, an active metabolite of oxybutynin. A clinical study in Japanese patients with primary palmar hyperhidrosis showed superiority of APOHIDE_® Lotion 20% over placebo, i.e., there were significantly more responders (i.e., patients with a reduction in sweat volume ≥50% from baseline) in the APOHIDE_® Lotion 20% group (APOHIDE_® Lotion 20% group: 52.8%, placebo group: 24.3%; treatment difference: 28.5%; P < 0.001, Fisher’s exact test). This and other clinical studies reported some adverse events (AEs) associated with the drug’s anticholinergic effects and some application site AEs, but most of the AEs were mild. Clinical response did not decrease with long-term (52-week) treatment, and only a few patients (2 of 125) discontinued treatment because of AEs. Taken together, study results indicate that APOHIDE_® Lotion 20% may be an effective and safe new treatment option for patients with primary palmar hyperhidrosis.

Futibatinib (Lytgobi_® Tablets 4 ‍mg), a novel fibroblast growth factor receptor (FGFR) inhibitor developed by Taiho Pharmaceutical using the Cysteinomix Drug Discovery Platform, was approved in Japan in June 2023 for the treatment of patients with unresectable biliary tract cancer with FGFR2 fusion or rearrangement that had progressed after at least one prior chemotherapy. Futibatinib covalently binds to the cysteine residue in the FGFR kinase domain P-loop structure and is believed to exert antitumor activity by selectively and irreversibly inhibiting FGFR1–4. Many FGFR inhibitors under development are ATP-competitive; however, futibatinib is the first approved covalently-binding irreversible FGFR inhibitor. It inhibits cell proliferation by inhibiting FGFR phosphorylation and its downstream signaling pathways in cancer cell lines. Futibatinib showed inhibitory activity against a wider range of FGFR mutants than ATP-competitive, reversible FGFR inhibitors and inhibited cell proliferation without significantly deviating from the inhibitory effect on wild-type FGFR. Futibatinib showed antitumor efficacy in mice subcutaneously transplanted with human tumor cell lines driven by FGFR. The international phase 2 study (TAS-120-101) was conducted in patients with refractory intrahepatic cholangiocarcinoma with FGFR2 fusion or rearrangement. The overall response rate was 41.7%, showing consistent efficacy regardless of co-occurring genomic alterations. Although some typical FGFR inhibitor-related side effects were observed, they were manageable and futibatinib had a good safety profile. Futibatinib is an important drug for biliary tract cancer, which has limited treatment options; its development is underway for other types of cancer, and it is expected to benefit more patients.