Tuft cell-derived acetylcholine regulates epithelial fluid secretion

Tuft cells are solitary chemosensory epithelial cells that can sense lumenal stimuli at mucosal barriers and secrete effector molecules to regulate the physiology and immune state of their surrounding tissue. In the small intestine, tuft cells detect parasitic worms (helminths) and microbe-derived succinate, and signal to immune cells to trigger a Type 2 immune response that leads to extensive epithelial remodeling spanning several days. Acetylcholine (ACh) from airway tuft cells has been shown to stimulate acute changes in breathing and mucocilliary clearance, but its function in the intestine is unknown. Here we show that tuft cell chemosensing in the intestine leads to release of ACh, but that this does not contribute to immune cell activation or associated tissue remodeling. Instead, tuft cell-derived ACh triggers immediate fluid secretion from neighboring epithelial cells into the intestinal lumen. This tuft cell-regulated fluid secretion is amplified during Type 2 inflammation, and helminth clearance is delayed in mice lacking tuft cell ACh. The coupling of the chemosensory function of tuft cells with fluid secretion creates an epithelium-intrinsic response unit that effects a physiological change within seconds of activation. This response mechanism is shared by tuft cells across tissues, and serves to regulate the epithelial secretion that is both a hallmark of Type 2 immunity and an essential component of homeostatic maintenance at mucosal barriers.

The discovery of (1R, 3R)-1-(3-chloro-5-fluorophenyl)-3-(hydroxymethyl)-1,2,3,4-tetrahydroisoquinoline-6-carbonitrile, a potent and selective agonist of human transient receptor potential cation channel subfamily m member 5 (TRPM5) and evaluation of as a potential gastrointestinal prokinetic agent

This publication details the discovery of a series of selective transient receptor potential cation channel subfamily M member 5 (TRPM5) agonists culminating with the identification of the lead compound (1R, 3R)-1-(3-chloro-5-fluorophenyl)-3-(hydroxymethyl)-1,2,3,4-tetrahydroisoquinoline-6-carbonitrile (39). We describe herein our biological rationale for agonism of the target, the examination of the then current literature tool molecules, and finally the process of our discovery starting with a high throughput screening hit through lead development. We also detail the selectivity of the lead compound 39 versus related family members TRPA1, TRPV1, TRPV4, TRPM4 and TRPM8, the drug metabolism and pharmacokinetics (DMPK) profile and in vivo efficacy in a mouse model of gastrointestinal motility.

Identification of positive modulators of TRPM5 channel from a high-throughput screen using a fluorescent membrane potential assay

Transient Receptor Potential Melastatin 5 (TRPM5) is an intracellular calcium-activated cation-selective ion channel expressed in a variety of cell types. Dysfunction of this channel has recently been implied in a range of disease states including diabetes, enteric infections, inflammatory responses, parasitic infection and other pathologies. However, to date, agonists and positive modulators of this channel with sufficient selectivity to enable target validation studies have not been described, limiting the evaluation of TRPM5 biology and its potential as a drug target. We developed a high-throughput assay using a fluorescent membrane potential dye and a medium- and high-throughput electrophysiology assay using QPatch HTX and SyncroPatch 384PE. By employing these assays, we conducted a primary screening campaign and identified hit compounds as TRPM5 channel positive modulators. An initial selectivity profile confirmed hit selectivity to TRPM5 and is presented here. These small molecule TRPM5 compounds have a high potential both as early tool compounds to enable pharmacological studies of TRPM5 and as starting points for the development of potent, selective TRPM5 openers or positive modulators as novel drugs targeting several pathological states.

Discovery of the Bruton's Tyrosine Kinase Inhibitor Clinical Candidate TAK-020 (S)-5-(1-((1-Acryloylpyrrolidin-3-yl)oxy)isoquinolin-3-yl)-2,4-dihydro-3H-1,2,4-triazol-3-one, by Fragment-Based Drug Design

This publication details the successful use of FBDD (fragment-based drug discovery) principles in the invention of a novel covalent Bruton's tyrosine kinase inhibitor, which ultimately became the Takeda Pharmaceuticals clinical candidate TAK-020. Described herein are the discovery of the fragment 5-phenyl-2,4-dihydro-3H-1,2,4-triazol-3-one, the subsequent optimization of this hit molecule to the candidate, and synthesis and performance in pharmacodynamic and efficacy models along with direct biophysical comparison of TAK-020 with other clinical-level assets and the marketed drug Ibrutinib.

Structures of the TRPM5 channel elucidate mechanisms of activation and inhibition

The Ca²⁺-activated TRPM5 channel plays essential roles in taste perception and insulin secretion. However, the mechanism by which Ca²⁺ regulates TRPM5 activity remains elusive. We report cryo-EM structures of the zebrafish TRPM5 in an apo closed state, a Ca²⁺-bound open state, and an antagonist-bound inhibited state. We define two novel ligand binding sites: a Ca²⁺ site (Ca_ICD) in the intracellular domain and an antagonist site in the transmembrane domain (TMD). The Ca_ICD site is unique to TRPM5 and has two roles: modulating the voltage dependence and promoting Ca²⁺ binding to the Ca_TMD site, which is conserved throughout TRPM channels. Conformational changes initialized from both Ca²⁺ sites cooperatively open the ion-conducting pore. The antagonist NDNA wedges into the space between the S1-S4 domain and pore domain, stabilizing the transmembrane domain in an apo-like closed state. Our results lay the foundation for understanding the voltage-dependent TRPM channels and developing new therapeutic agents.

Biochemical and Cellular Profile of NIK Inhibitors with Long Residence Times

Two different signaling pathways lead to the activation of the transcription factor NF-κB, initiating distinct biological responses: The canonical NF-κB pathway activation has been implicated in host immunity and inflammatory responses, whereas the noncanonical pathway activation has been involved in lymphoid organ development and B-cell maturation, as well as in the development of chronic inflammatory diseases and some hematologic cancers. The NF-κB-inducing kinase (NIK) is a cytoplasmic Ser/Thr kinase and is a key regulator of the noncanonical pathway. NIK activation results in the processing of the p100 subunit to p52, leading to the formation of the RelB/p52 complex and noncanonical pathway activation. Because of its role in the development of lymphoid malignancies, this kinase has always been considered as an attractive target for the treatment of certain types of cancers and immune diseases. We at Takeda have pursued a drug discovery program to identify small-molecule inhibitors against NIK. This report provides an overview of the data generated from our screening campaign using a small fragment library. Most importantly, we also provide a kinetic analysis of published compounds and chemical series developed at Takeda that are associated with a slow tight-binding mechanism and excellent cellular potency.

From High-Throughput Screening to Target Validation: Benzo[d]isothiazoles as Potent and Selective Agonists of Human Transient Receptor Potential Cation Channel Subfamily M Member 5 Possessing In Vivo Gastrointestinal Prokinetic Activity in Rodents

Transient receptor potential cation channel subfamily M member 5 (TRPM5) is a nonselective monovalent cation channel activated by intracellular Ca²⁺ increase. Within the gastrointestinal system, TRPM5 is expressed in the stoma, small intestine, and colon. In the search for a selective agonist of TRPM5 possessing in vivo gastrointestinal prokinetic activity, a high-throughput screening was performed and compound 1 was identified as a promising hit. Hit validation and hit to lead activities led to the discovery of a series of benzo[d]isothiazole derivatives. Among these, compounds 61 and 64 showed nanomolar activity and excellent selectivity (>100-fold) versus related cation channels. The in vivo drug metabolism and pharmacokinetic profile of compound 64 was found to be ideal for a compound acting locally at the intestinal level, with minimal absorption into systemic circulation. Compound 64 was tested in vivo in a mouse motility assay at 100 mg/kg, and demonstrated increased prokinetic activity.

Structure-guided optimization of a novel class of ASK1 inhibitors with increased sp3 character and an exquisite selectivity profile

Apoptosis Signal-Regulating Kinase-1 (ASK1) is a known member of the Mitogen-Activated Protein Kinase Kinase Kinase (MAP3K) family and upon stimulation will activate the p38- and JNK-pathways leading to cardiac apoptosis, fibrosis, and hypertrophy. Using Structure-Based Drug Design (SBDD) in parallel with deconstruction of a published compound, a novel series of ASK1 inhibitors was optimized, which incorporated a saturated heterocycle proximal to the hinge-binding motif. This yielded a unique chemical series with excellent selectivity across the broader kinome, and desirable drug-like properties. The lead compound (10) is highly soluble and permeable, and exhibits a cellular EC₅₀ = 24 nM and K_d < 1 nM. Of the 350 kinases tested, 10 has an IC₅₀ ≤ 500 nM for only eight of them. This paper will describe the design hypotheses behind this series, key data points during the optimization phase, as well as a possible structural rationale for the kinome selectivity. Based on crystallographic data, the presence of an aliphatic cycle adjacent to the hinge-binder in the active site of the protein kinase showed up in <1% of the >5000 structures in the Protein Data Bank, potentially conferring the selectivity seen in this series.

Comparison of Two Methods of Pancreas Islets Immunoisolation

The efficacy of two methods of Langerhans islets immunoisolation was compared. For this purpose the function of islets encapsulated with alginate/polyethylenimine/protamine/heparin (APPH) or with alginate/poly-L-lisine/alginate (APA) membranes was assessed: in vitro according to their survival and response to glucose challenges, and in vivo according to their capability to provide sufficient insulin delivery to maintain normal fasting blood glucose following xenotransplantation to streptozotocin diabetic mice. In vitro insulin secretion and the response to glucose challenge of APPH and APA encapsulated islets were comparable to free islets. In vivo intraperitoneal concordant xenotransplantation of APA encapsulated rat islets reversed the diabetic state of streptozotocin diabetic mice for a longer period, than APPH islet grafts. This study clearly demonstrated the inadequacy of in vitro methods in the prediction of in vivo results of islets transplantation.

Correction to "Structure-Based Design of ASK1 Inhibitors as Potential Agents for Heart Failure"

[This corrects the article DOI: 10.1021/acsmedchemlett.6b00481.].

Structure-Based Design of ASK1 Inhibitors as Potential Agents for Heart Failure

Apoptosis signal-regulating kinase 1 (ASK1/MAP3K) is a mitogen-activated protein kinase family member shown to contribute to acute ischemia/reperfusion injury. Using structure-based drug design, deconstruction, and reoptimization of a known ASK1 inhibitor, a lead compound was identified. This compound displayed robust MAP3K pathway inhibition and reduction of infarct size in an isolated perfused heart model of cardiac injury.

Design, synthesis and optimization of novel Alk5 (activin-like kinase 5) inhibitors

Using SBDD, a series of 4-amino-7-azaindoles were discovered as a novel class of Alk5 inhibitors that are potent in both Alk5 enzymatic and cellular assays. Subsequently a ring cyclization strategy was utilized to improve ADME properties leading to the discovery of a series of 1H-imidazo[4,5-c]pyridin-2(3H)-one drug like Alk5 inhibitors.

Fragment-Based Discovery of a Small Molecule Inhibitor of Bruton's Tyrosine Kinase

The discovery and optimization of a series of 4-aminocinnoline-3-carboxamide inhibitors of Bruton's tyrosine kinase are reported. A fragment-based screening approach incorporating X-ray co-crystallography was used to identify a cinnoline fragment and characterize its binding mode in the ATP binding site of Btk. Optimization of the fragment hit resulted in the identification of a lead compound which reduced paw swelling in a dose- and exposure-dependent fashion in a rat model of collagen-induced arthritis.

Histomorphometrical analysis of porcine islets of Langerhans

Xenotransplantation of pig islets of Langerhans may be an efficient method for treatment of type I diabetic patients. Considering the shortage of human pancreas donors, pigs offer readily available islet source. Unfortunately, their morphologic characteristics makes isolation of pig islets of Langerhans extremely difficult. The selection of a suitable donor may favorably affect the success of isolation. Therefore, we examined pig breeds and weights for their influence histomorphometric features of Langerhans islets. Pancreatic tissue biopsy specimens were obtained from Polish Large White pigs (n=5), Polish Landrace pigs (n=8), Pietrain pigs (n=4), and marked-weight pigs of 100 kg (n=8) or more than 200 kg (n=10). Biopsy specimens were fixed and stored in 4% formaldehyde. Tissue sections were stained with polyclonal guinea pig anti-insulin antibody. The number of islets per 1 cm2 was counted in each section. Mean diameters and areas of the islets were measured to calculate the percentage volume density. Differences were observed among the groups of pigs weighing 200 kg and 100 kg in islet mean diameter and area. The number of islets/cm2 was higher among Pietrain than Polish Landrace pigs (425.45±111.7 versus 315.33±36.59 islet/cm2, P<.05). Furthermore, Pietrain pigs showed the largest volume density (1.44%). Histological analysis revealed that Pietrain pigs of 100 kg and market-weight pigs of 200 kg were the best donors for islets of Langerhans.

The development of novel C-2, C-8, and N-9 trisubstituted purines as inhibitors of TNF-α production

A series of C-2, C-8, and N-9 trisubstituted purine based inhibitors of TNF-alpha production are described. The most potent analogs showed low nanomolar activity against LPS-induced TNF-alpha production in a THP-1 cell based assay. The SAR of the series was optimized with the aid of X-ray co-crystal structures of these inhibitors bound with mutated p38 (mp38).

The development of novel 1,2-dihydro-pyrimido[4,5-c]pyridazine based inhibitors of lymphocyte specific kinase (Lck)

This communication details the synthesis, biological activity, and proposed binding mode of a novel class of tri-cyclic derivatives of 1,2-dihydro-pyrimido[4,5-c]pyridazines 1 and 2. The most potent analogs disclosed showed low nanomolar activity for the inhibition of Lck kinase.

Development of N-4,6-pyrimidine-N-alkyl-N'-phenyl ureas as orally active inhibitors of lymphocyte specific tyrosine kinase

A new class of lymphocyte specific tyrosine kinase (lck) inhibitors based on an N-4,6-pyrimidine-N-alkyl-N'-phenyl urea scaffold is described. Many of these compounds showed low-nanomolar inhibition of lck kinase activity as well as IL-2 synthesis from Jurkat cells. One of these analogs, 7i, was shown to be orally efficacious by in vivo testing in a rat adjuvant-induced arthritis study.

Development of N-2,4-pyrimidine-N-phenyl-N'-phenyl ureas as inhibitors of tumor necrosis factor alpha (TNF-alpha) synthesis. Part 1

A new class of tumor necrosis factor alpha (TNF-alpha) synthesis inhibitors based on an N-2,4-pyrimidine-N-phenyl-N'-phenyl urea scaffold is described. Many of these compounds showed low-nanomolar activity against lipopolysaccharide stimulated TNF-alpha production. X-ray co-crystallization studies with mutated p38alpha showed that these trisubstituted ureas interact with the ATP-binding pocket in a pseudo-bicyclic conformation brought about by the presence of an intramolecular hydrogen bonding interaction.

Development of N-2,4-pyrimidine-N-phenyl-N'-alkyl ureas as orally active inhibitors of tumor necrosis factor alpha (TNF-alpha) synthesis. Part 2

A new class of tumor necrosis factor alpha (TNF-alpha) synthesis inhibitors based on a N-2,4-pyrimidine-N-phenyl-N'-alkyl urea scaffold is described. Many of these compounds showed low-nanomolar activity against lipopolysaccharide stimulated TNF-alpha production. Two analogs were tested in an in vivo rat iodoacetate model of osteoarthritis and shown to be orally efficacious. X-ray co-crystallization studies with mutated p38alpha showed that these trisubstituted ureas interact with the ATP-binding pocket in a pseudo-bicyclic conformation brought about by the presence of an intramolecular hydrogen bonding interaction.

The development of new isoxazolone based inhibitors of tumor necrosis factor-alpha (TNF-α) production

4-Aryl-3-pyridyl and 4-aryl-3-pyrimidinyl based tumor necrosis factor-alpha (TNF-alpha) inhibitors, which contain a novel isoxazolone five-membered heterocyclic core are described. Many showed sub-micromolar activity against lipopolysaccharide-induced TNF-alpha production.

The development of new bicyclic pyrazole-based cytokine synthesis inhibitors

4-Aryl-5-pyrimidyl-based cytokine synthesis inhibitors of TNF-alpha production, which contain a novel bicyclic pyrazole heterocyclic core, are described. Many of these inhibitors showed low nanomolar activity against LPS-induced TNF-alpha production in a THP-1 cell-based assay and against human p38 alpha MAP kinase in an isolated enzyme assay. The X-ray crystal structure of a bicyclic pyrazole inhibitor co-crystallized with mutated p38 (mp38) is presented.

A prospective study of the incidence of skin cancer and its risk factors in a Spanish Mediterranean population of kidney transplant recipients

BACKGROUND

Skin cancer is the most common malignancy occurring in kidney transplant recipients (KTRs).

OBJECTIVES

Our purpose was to investigate, prospectively, the cumulative incidence of cancerous and precancerous skin lesions as well as their risk factors in a close follow-up population of KTRs from a Mediterranean area of Spain.

PATIENTS AND METHODS

One hundred and seventy-four consecutive KTRs were examined at the moment of transplant and then at 6-month intervals. The cumulative incidence of skin cancer was computed. To analyse the role of potential risk factors (age at transplantation, cause of renal failure, duration of pretransplant dialysis, type of immunosuppressive regimen, sun-reactive skin type and history of occupational sun exposure), the Cox regression method was used.

RESULTS

After a median follow-up of 72 months (range, 12-140), 39 patients (25.3%) developed 142 tumours [84 basal cell carcinoma (BCC) and 58 squamous cell carcinoma (SCC)]. The BCC/SCC ratio was 1.4 : 1. The cumulative incidence for skin cancer was 13% after 3 years of graft survival, increasing to 27.5% at 6 years and 48% at 10 years. Only age at the time of transplantation and occupational sun exposure had statistical significance as risk factors (P < 0.001).

CONCLUSIONS

Our study confirms the high incidence of non-melanoma skin cancer among KTRs in a Mediterranean population with occupational sun exposure and the patient's age at the time of transplantation being the main risk factors. We believe that all organ transplant programs should provide educational information about protecting oneself from the sun as well as include follow-up visits by dermatologists in order to facilitate early diagnosis and treatment of skin cancer.

Assessment of some porcine strains as donors of islets of langerhans

Mass isolation of viable porcine islets is a difficult task because of their fragility, and because of donor variability with respect to strain, age, sex, feeding, and methods of slaughtering. Not all strains are equally suitable for islet separation. The aim of this study was to evaluate porcine pancreata as an alternative source of islets for clinical transplantation. Pancreata were digested from pig strains available in Poland: 248 market weight slaughterhouse pigs and 42 pigs, belonging to the Polish Large White (WBP, 14 sows and 3 males), Polish White Pendant-Ears (PBZ; 16 sows), Pietrain (8 sows), and Yorkshire (1 sow) races. Prepurification data of recoverable islets/g and islet equivalents/g were considered as representative for the number of recoverable islets. Acceptable results namely, islet and/or islet-equivalent (IE) number of at least 1000/g, were obtained from only 56 of 248 slaughterhouse pigs, namely 2073 +/- 137.4 SE (median 1767/g) islets with values of IE of 2994 +/- 303 SE (median 1874/g). Our data support Krickhahn et al suggesting that only pancreata with an average islet size exceeding 199 microm should be digested and that only from 1 of 3 to 5 porcine pancreata is an adequate amount of islets generated.

Coordination polymers of copper(I) halides

A total of 21 complexes of CuX (X = Cl, Br, I) with bridging ligand (B = 4,4'-dipyridyl (Bpy), pyrazine (Pyz), quinoxaline (Quin), phenazine (Phz), 1,4-diazabicyclo[2.2.2]octane (DABCO), and hexamethylenetetramine (HMTA)) have been synthesized. The products show two stoichiometries: [CuXB] (type 1) and [(CuX)2B] (type 2). Both types can be obtained for B = Bpy, depending on the conditions of preparation. In these cases, the type 2 stoichiometry is the kinetic product. Type 2 complexes only are found for B = Pyz (X = I), Quin, Phz, DABCO, and HMTA. Type 1 complexes form for Pyz (X = Cl, Br). Thermogravimetic analyses of the complexes reveal the general decomposition trend: 1 --> 2 --> [(CuX)2B(1/2)] --> CuX. The X-ray crystal structure of [CuBr(Pyz)] (type 1) features copper atoms bridged by Br and Pyz, forming 2D sheets of fused rectangular Cu4Br2(Pyz)2 units. The X-ray structure of [(CuI)2(Quin)] (type 2) shows 2D layers composed of [Cu2I2]infinity "stair step" chains which are cross-linked by Quin ligands. A total of 16 complexes of CuXL (L = P(OPh)3) with bridging ligand (B = those above and 1,4-dimethylpiperazine (DMP)) have also been prepared. All of these products, except those of HMTA, are of type 3 formulation, [(CuXL)2B]. The HMTA products have the formula [CuX(HMTA)], type 4. Thermal decomposition of the type 3 and 4 complexes occurs with initial loss of B, L, or both. The X-ray structures of [(CuBrL)2(Bpy)] and [(CuBrL)2(Pyz)] (type 3) reveal 1D chains formed from rhomboidal (LCu)2Br2 units linked by the B ligand. The type 4 structure of [CuBrL(HMTA)] is shown by X-ray to be a simple halide-bridged dimer.

A new 7,8-euphadien-type triterpenoid from Brackenridgea nitida and Bleasdalea bleasdalei that inhibits DNA polymerase beta

Bioassay-guided fractionation of extracts prepared from Brackenridgea nitida and Bleasdalea bleasdalei, using an assay to detect DNA polymerase beta inhibition, resulted in the isolation of the inhibitory principle, (24E)-3beta-hydroxy-7,24-euphadien-26-oic acid (1), a new euphane triterpenoid. The structure of 1 was established on the basis of HRMS and 1D and 2D NMR spectroscopic methods and was confirmed further by X-ray crystallographic analysis. Compound 1 inhibited rat DNA polymerase beta with an IC(50) value of 23 microM in the presence of bovine serum albumin (BSA) and 9.7 microM in the absence of BSA, consistent with the possibility that 1 may be of utility in vivo. This possibility was further supported by the finding that 1 potentiated the inhibitory action of the anticancer drug bleomycin in cultured P-388D(1) cells, reducing the number of viable cells by 48% when employed at a concentration of 25 microM in the presence of an otherwise nontoxic (75 nM) concentration of bleomycin. Compound 1 is the first euphane-type triterpenoid found to inhibit DNA polymerase beta.