Discovery of Selective and Orally Available Galectin-1 Inhibitors

A new series of orally available α-d-galactopyranosides with high affinity and specificity toward galectin-1 have been discovered. High affinity and specificity were achieved by changing six-membered aryl-triazolyl substituents in a series of recently published galectin-3-selective α-d-thiogalactosides (e.g., GB1107 Kd galectin-1/3 3.7/0.037 μM) for five-membered heterocycles such as thiazoles. The in vitro pharmacokinetic properties were optimized, resulting in several galectin-1 inhibitors with favorable properties. One compound, GB1490 (Kd galectin-1/3 0.4/2.7 μM), was selected for further characterization toward a panel of galectins showing a selectivity of 6- to 320-fold dependent on galectin. The X-ray structure of GB1490 bound to galectin-1 reveals the compound bound in a single conformation in the carbohydrate binding site. GB1490 was shown to reverse galectin-1-induced apoptosis of Jurkat cells at low μM concentrations. No cell cytotoxicity was observed for GB1490 up to 90 μM in the A549 cells. In pharmacokinetic studies in mice, GB1490 showed high oral bioavailability (F% > 99%).

Resistance to anti-PD-1/anti-PD-L1: galectin-3 inhibition with GB1211 reverses galectin-3-induced blockade of pembrolizumab and atezolizumab binding to PD-1/PD-L1

Background

Galectin-3 (Gal-3) is a β-galactoside-binding lectin that is highly expressed within the tumor microenvironment of aggressive cancers and has been suggested to predict a poor response to immune checkpoint therapy with the anti-PD-1 monoclonal antibody pembrolizumab. We aimed to assess if the effect of Gal-3 was a result of direct interaction with the immune checkpoint receptor.

Methods

The ability of Gal-3 to interact with the PD-1/PD-L1 complex in the absence and presence of blocking antibodies was assessed in in vitro biochemical and cellular assays as well as in an in vivo syngeneic mouse cancer model.

Results

Gal-3 reduced the binding of the checkpoint inhibitors pembrolizumab (anti-PD-1) and atezolizumab (anti-PD-L1), by potentiating the interaction between the PD-1/PD-L1 complex. In the presence of a highly selective Gal-3 small molecule inhibitor (GB1211) the binding of the anti-PD-1/anti-PD-L1 therapeutics was restored to control levels. This was observed in both a surface plasmon resonance assay measuring protein-protein interactions and via flow cytometry. Combination therapy with GB1211 and an anti-PD-L1 blocking antibody reduced tumor growth in an in vivo syngeneic model and increased the percentage of tumor infiltrating T lymphocytes.

Conclusion

Our study suggests that Gal-3 can potentiate the PD-1/PD-L1 immune axis and potentially contribute to the immunosuppressive signalling mechanisms within the tumor microenvironment. In addition, Gal-3 prevents atezolizumab and pembrolizumab target engagement with their respective immune checkpoint receptors. Reversal of this effect with the clinical candidate GB1211 offers a potential enhancing combination therapeutic with anti-PD-1 and -PD-L1 blocking antibodies.

Evaluating the affinity and kinetics of small molecule glycomimetics for human and mouse galectin-3 using surface plasmon resonance

Galectin-3 is a beta-galactoside-binding mammalian lectin that is one of a 15-member galectin family that can bind several cell surface glycoproteins via its carbohydrate recognition domain (CRD). As a result, it can influence a range of cellular processes including cell activation, adhesion and apoptosis. Galectin-3 has been implicated in various diseases, including fibrotic disorders and cancer, and is now being therapeutically targeted by both small and large molecules. Historically, the screening and triaging of small molecule glycomimetics that bind to the galectin-3 CRD has been completed in fluorescence polarisation (FP) assays to determine KD values. Surface plasmon resonance (SPR) has not been widely used for compound screening and in this study it was used to compare human and mouse galectin-3 affinity measures between FP and SPR, as well as investigate compound kinetics. The KD estimates for a set of compounds selected from mono- and di-saccharides with affinities across a 550-fold range, correlated well between FP and SPR assay formats for both human and mouse galectin-3. Increases in affinity for compounds binding to human galectin-3 were driven by changes in both kon and koff whilst for mouse galectin-3 this was primarily due to kon. The reduction in affinity observed between human to mouse galectin-3 was also comparable between assay formats. SPR has been shown to be a viable alternative to FP for early drug discovery screening and determining KD values. In addition, it can also provide early kinetic characterisation of small molecule galectin-3 glycomimetics with robust kon and koff values generated in a high throughput manner.

Connectomic Basis for Tremor Control in Stereotactic Radiosurgical Thalamotomy

BACKGROUND AND PURPOSE

Given the increased use of stereotactic radiosurgical thalamotomy and other ablative therapies for tremor, new biomarkers are needed to improve outcomes. Using resting-state fMRI and MR tractography, we hypothesized that a "connectome fingerprint" can predict tremor outcomes and potentially serve as a targeting biomarker for stereotactic radiosurgical thalamotomy.

MATERIALS AND METHODS

We evaluated 27 patients who underwent unilateral stereotactic radiosurgical thalamotomy for essential tremor or tremor-predominant Parkinson disease. Percentage postoperative improvement in the contralateral limb Fahn-Tolosa-Marin Clinical Tremor Rating Scale (TRS) was the primary end point. Connectome-style resting-state fMRI and MR tractography were performed before stereotactic radiosurgery. Using the final lesion volume as a seed, "connectivity fingerprints" representing ideal connectivity maps were generated as whole-brain R-maps using a voxelwise nonparametric Spearman correlation. A leave-one-out cross-validation was performed using the generated R-maps.

RESULTS

The mean improvement in the contralateral tremor score was 55.1% (SD, 38.9%) at a mean follow-up of 10.0 (SD, 5.0) months. Structural connectivity correlated with contralateral TRS improvement (r = 0.52; P  = .006) and explained 27.0% of the variance in outcome. Functional connectivity correlated with contralateral TRS improvement (r = 0.50; P  = .008) and explained 25.0% of the variance in outcome. Nodes most correlated with tremor improvement corresponded to areas of known network dysfunction in tremor, including the cerebello-thalamo-cortical pathway and the primary and extrastriate visual cortices.

CONCLUSIONS

Stereotactic radiosurgical targets with a distinct connectivity profile predict improvement in tremor after treatment. Such connectomic fingerprints show promise for developing patient-specific biomarkers to guide therapy with stereotactic radiosurgical thalamotomy.

Discovery and Optimization of the First Highly Effective and Orally Available Galectin-3 Inhibitors for Treatment of Fibrotic Disease

Galectin-3 is a carbohydrate-binding protein central to regulating mechanisms of diseases such as fibrosis, cancer, metabolic, inflammatory, and heart disease. We recently found a high affinity (nM) thiodigalactoside GB0139 which currently is in clinical development (PhIIb) as an inhaled treatment of idiopathic pulmonary fibrosis. To enable treatment of systemically galectin-3 driven disease, we here present the first series of selective galectin-3 inhibitors combining high affinity (nM) with oral bioavailability. This was achieved by optimizing galectin-3 specificity and physical chemical parameters for a series of disubstituted monogalactosides. Further characterization showed that this class of compounds reduced profibrotic gene expression in liver myofibroblasts and displayed antifibrotic activity in CCl₄-induced liver fibrosis and bleomycin-induced lung fibrosis mouse models. On the basis of the overall pharmacokinetic, pharmacodynamic, and safety profile, GB1211 was selected as the clinical candidate and is currently in phase IIa clinical trials as a potential therapy for liver cirrhosis and cancer.

Resistance to anti-PD-1/anti-PD-L1: GB1211 reverses galectin-3 induced blockade of pembrolizumab and atezolizumab binding to PD-1/PD-L1

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Background: Galectin-3 (Gal-3) is a β-galactoside binding lectin highly expressed across many cancers (Li et al. Biomedicines, 2021) with high expression associated with poor response to the PD-1 inhibitor pembrolizumab (Capalbo et al., Int J Mol Sci, 2019). In addition, it has also been shown preclinically in in vivo mouse non-small cell lung carcinoma (NSCLC) models that inhibition of Gal-3 enhances the performance of checkpoint inhibitors targeting the PD-1/PD-L1 axis (Vuong et al., Cancer Res, 2019; Zhang et al., FEBS Open Bio, 2020). The mechanism by which Gal-3 negatively impacts the effect of PD-1/PD-L1 based checkpoint inhibitors is not fully understood. We investigated the hypothesis that anti-PD1/anti-PDL1 is induced by direct binding and blockade of Gal-3 to the PD-1/PD-L1 complex itself. Methods: SPR was used to investigate the effect of recombinant hGal-3 in combination with a Gal-3 inhibitor (GB1211) on the binding of recombinant hPD-L1 to hPD-1 in the absence and presence of either pembrolizumab or atezolizumab. SPR analysis was performed with a BIAcore (Cytiva, USA). hPD-1 was immobilized onto a CM5 Series S sensorchip via amine coupling and proteins, antibodies or small molecules flowed over in various combinations. Observations made at the protein level were further confirmed in cell binding assays using flow cytometry measuring pembrolizumab and atezolizumab binding to cells lines over expressing high levels of either PD-1 (Jurkat cells) or PD-L1 (RAJI-hPD-L1 cells), respectively. Results: Gal-3 potentiated the binding of PD-L1 to PD-1 with a 3-fold increase in its KD observed and the efficiency of pembrolizumab and atezolizumab binding to and blocking the PD-1/PD-L1 axis was reduced. A 6-fold reduction in KD of pembrolizumab for the PD-1/PD-L1 complex was observed in the presence of Gal-3. In addition, atezolizumab PD-L1 blockade was reversed in the presence of Gal-3 and dramatically improved by GB1211. Similarly, in cell systems expressing high levels of PD-1 or PD-L1, Gal-3 reduced the binding of pembrolizumab and atezolizumab to their respective targets on cell surfaces that was also reversed by GB1211. Conclusions: Gal-3 was shown to vastly reduce the binding of the checkpoint inhibitors pembrolizumab and atezolizumab, by potentiating the interaction between PD-1 and PD-L1. GB1211 restored the binding of the anti-PD1/anti-PDL1 therapeutics and may thus reduce tumor resistance to these agents. These findings harmonize excellently with in vivo and clinical data showing an association between Gal-3 expression and lack of efficacy of PD-1/PD-L1 targeted checkpoint inhibitors. Galecto is now investigating the safety and efficacy of GB1211 in combination with atezolizumab in NSCLC.

Integrins as a drug target in liver fibrosis

As the worldwide prevalence of chronic liver diseases is high and continuing to increase, there is an urgent need for treatment to prevent cirrhosis-related morbidity and mortality. Integrins are heterodimeric cell-surface proteins that are promising targets for therapeutic intervention. αv integrins are central in the development of fibrosis as they activate latent TGFβ, a known profibrogenic cytokine. The αv subunit can form heterodimers with β1, β3, β5, β6 or β8 subunits and one or more of these integrins are central to the development of liver fibrosis, however, their relative importance is not understood. This review summarises the current knowledge of αv integrins and their respective β subunits in different organs, with a focus on liver fibrosis and the emerging preclinical and clinical data with regards to αv integrin inhibitors.

Pharmacological characterisation of GSK3335103, an oral αvβ6 integrin small molecule RGD-mimetic inhibitor for the treatment of fibrotic disease

Fibrosis is the formation of scar tissue due to injury or long-term inflammation and is a leading cause of morbidity and mortality. Activation of the pro-fibrotic cytokine transforming growth factor-β (TGFβ) via the alpha-V beta-6 (αvβ6) integrin has been identified as playing a key role in the development of fibrosis. Therefore, a drug discovery programme to identify an orally bioavailable small molecule αvβ6 arginyl-glycinyl-aspartic acid (RGD)-mimetic was initiated. As part of a medicinal chemistry programme GSK3335103 was identified and profiled in a range of pre-clinical in vitro and in vivo systems. GSK3335103 was shown to bind to the αvβ6 with high affinity and demonstrated fast binding kinetics. In primary human lung epithelial cells, GSK3335103-induced concentration- and time-dependent internalisation of αvβ6 with a rapid return of integrin to the cell surface observed after washout. Following sustained engagement of the αvβ6 integrin in vitro, lysosomal degradation was induced by GSK3335103. GSK3335103 was shown to engage with the αvβ6 integrin and inhibit the activation of TGFβ in both ex vivo IPF tissue and in a murine model of bleomycin-induced lung fibrosis, as measured by αvβ6 engagement, TGFβ signalling and collagen deposition, with a prolonged duration of action observed in vivo. In summary, GSK3335103 is a potent αvβ6 inhibitor that attenuates TGFβ signalling in vitro and in vivo with a well-defined pharmacokinetic/pharmacodynamic relationship. This translates to a significant reduction of collagen deposition in vivo and therefore GSK3335103 represents a potential novel oral therapy for fibrotic disorders.

Emerging therapeutic opportunities for integrin inhibitors

Integrins are cell adhesion and signalling proteins crucial to a wide range of biological functions. Effective marketed treatments have successfully targeted integrins αIIbβ3, α4β7/α4β1 and αLβ2 for cardiovascular diseases, inflammatory bowel disease/multiple sclerosis and dry eye disease, respectively. Yet, clinical development of others, notably within the RGD-binding subfamily of αv integrins, including αvβ3, have faced significant challenges in the fields of cancer, ophthalmology and osteoporosis. New inhibitors of the related integrins αvβ6 and αvβ1 have recently come to the fore and are being investigated clinically for the treatment of fibrotic diseases, including idiopathic pulmonary fibrosis and nonalcoholic steatohepatitis. The design of integrin drugs may now be at a turning point, with opportunities to learn from previous clinical trials, to explore new modalities and to incorporate new findings in pharmacological and structural biology. This Review intertwines research from biological, clinical and medicinal chemistry disciplines to discuss historical and current RGD-binding integrin drug discovery, with an emphasis on small-molecule inhibitors of the αv integrins.

Integrins are key signalling molecules that are present on the surface of subsets of cells and are therefore good potential therapeutic targets. In this Review, Hatley and colleagues discuss the development of integrin inhibitors, particularly the challenges in developing inhibitors for integrins that contain an αv-subunit, and suggest how these challenges could be addressed.

Downregulation of the αvβ6 Integrin via RGD Engagement Is Affinity and Time Dependent

The arginyl-glycinyl-aspartic acid (RGD) integrin alpha-v beta-6 (αvβ6) has been identified as playing a key role in the activation of transforming growth factor-β (TGFβ) that is hypothesized to be pivotal in the development of fibrosis and other diseases. In this study, αvβ6 small molecule inhibitors were characterized in a range of in vitro systems to determine affinity, kinetics, and duration of TGFβ inhibition. High αvβ6 binding affinity was shown to be correlated with slow dissociation kinetics. Compound 1 (high αvβ6 affinity, slow dissociation) and SC-68448 (low αvβ6 affinity, fast dissociation) induced concentration- and time-dependent internalization of αvβ6 in normal human bronchial epithelial (NHBE) cells. After washout, the αvβ6 cell surface repopulation was faster for SC-68448 compared with compound 1 In addition, αvβ6-dependent release of active TGFβ from NHBE cells was inhibited by compound 1 and SC-68448. After washout of SC-68448, release of active TGFβ was restored, whereas after washout of compound 1 the inhibition of TGFβ activation was maintained and only reversible in the presence of a lysosomal inhibitor (chloroquine). However, SC-68448 was able to reduce total levels of αvβ6 in NHBE cells if present continuously. These observations suggest αvβ6 can be degraded after high affinity RGD binding that sorts the integrin for lysosomal degradation after internalization, likely due to sustained engagement as a result of slow dissociation kinetics. In addition, the αvβ6 integrin can also be downregulated after sustained engagement of the RGD binding site with low affinity ligands that do not sort the integrin for immediate lysosomal degradation. SIGNIFICANCE STATEMENT: The fate of RGD integrin after ligand binding has not been widely investigated. Using the αvβ6 integrin as a case study, we have demonstrated that RGD-induced downregulation of αvβ6 is both affinity and time dependent. High affinity ligands induced downregulation via lysosomal degradation, likely due to slow dissociation, whereas sustained low affinity ligand engagement was only able to decrease αvβ6 expression over longer periods of time. Our study provides a potential unique mechanism for obtaining duration of action for drugs targeting integrins.

Translational pharmacology of an inhaled small molecule αvβ6 integrin inhibitor for idiopathic pulmonary fibrosis

The αvβ6 integrin plays a key role in the activation of transforming growth factor-β (TGFβ), a pro-fibrotic mediator that is pivotal to the development of idiopathic pulmonary fibrosis (IPF). We identified a selective small molecule αvβ6 RGD-mimetic, GSK3008348, and profiled it in a range of disease relevant pre-clinical systems. To understand the relationship between target engagement and inhibition of fibrosis, we measured pharmacodynamic and disease-related end points. Here, we report, GSK3008348 binds to αvβ6 with high affinity in human IPF lung and reduces downstream pro-fibrotic TGFβ signaling to normal levels. In human lung epithelial cells, GSK3008348 induces rapid internalization and lysosomal degradation of the αvβ6 integrin. In the murine bleomycin-induced lung fibrosis model, GSK3008348 engages αvβ6, induces prolonged inhibition of TGFβ signaling and reduces lung collagen deposition and serum C3M, a marker of IPF disease progression. These studies highlight the potential of inhaled GSK3008348 as an anti-fibrotic therapy.

The αvβ6 integrin is key in activating the pro-fibrotic cytokine TGFβ in idiopathic pulmonary fibrosis. Here, the authors show an inhaled small molecule αvβ6 inhibitor GSK3008348 induces prolonged inhibition of TGFβ signaling pathways in human and murine models of lung fibrosis via αvβ6 degradation.

Chlorhexidine hexametaphosphate as a wound care material coating: antimicrobial efficacy, toxicity and effect on healing

Aim: In this study, chlorhexidine hexametaphosphate (CHX-HMP) is investigated as a persistent antimicrobial coating for wound care materials. Materials & methods: CHX-HMP was used as a wound care material coating and compared with chlorhexidine digluconate materials with respect to antimicrobial efficacy, toxicity and wound closure. Results: Antimicrobial efficacy at day 1, 3 and 7 was observed with experimental and commercial materials. CHX-HMP coated materials had less toxic effect on human placental cells than commercial chlorhexidine dressings. CHX-HMP in pluronic gel did not delay healing but reduced wound colonization by E. faecalis. Conclusion: CHX-HMP could become a useful component of wound care materials with sustained antimicrobial efficacy, lower toxicity than chlorhexidine digluconate materials, and reduction in wound colonization without affecting closure.

Coronin-1C Protein and Caveolin Protein Provide Constitutive and Inducible Mechanisms of Rac1 Protein Trafficking

Sustained directional fibroblast migration requires both polarized activation of the protrusive signal, Rac1, and redistribution of inactive Rac1 from the rear of the cell so that it can be redistributed or degraded. In this work, we determine how alternative endocytic mechanisms dictate the fate of Rac1 in response to the extracellular matrix environment. We discover that both coronin-1C and caveolin retrieve Rac1 from similar locations at the rear and sides of the cell. We find that coronin-1C-mediated extraction, which is responsible for Rac1 recycling, is a constitutive process that maintains Rac1 protein levels within the cell. In the absence of coronin-1C, the effect of caveolin-mediated endocytosis, which targets Rac1 for proteasomal degradation, becomes apparent. Unlike constitutive coronin-1C-mediated trafficking, caveolin-mediated Rac1 endocytosis is induced by engagement of the fibronectin receptor syndecan-4. Such an inducible endocytic/degradation mechanism would predict that, in the presence of fibronectin, caveolin defines regions of the cell that are resistant to Rac1 activation but, in the absence of fibronectin leaves more of the membrane susceptible to Rac1 activation and protrusion. Indeed, we demonstrate that fibronectin-stimulated activation of Rac1 is accelerated in the absence of caveolin and that, when caveolin is knocked down, polarization of active Rac1 is lost in FRET experiments and culminates in shunting migration in a fibrous fibronectin matrix. Although the concept of polarized Rac1 activity in response to chemoattractants has always been apparent, our understanding of the balance between recycling and degradation explains how polarity can be maintained when the chemotactic gradient has faded.

Coronin-1C and RCC2 guide mesenchymal migration by trafficking Rac1 and controlling GEF exposure

Sustained forward migration through a fibrillar extracellular matrix requires localization of protrusive signals. Contact with fibronectin at the tip of a cell protrusion activates Rac1, and for linear migration it is necessary to dampen Rac1 activity in off-axial positions and redistribute Rac1 from non-protrusive membrane to the leading edge. Here, we identify interactions between coronin-1C (Coro1C), RCC2 and Rac1 that focus active Rac1 to a single protrusion. Coro1C mediates release of inactive Rac1 from non-protrusive membrane and is necessary for Rac1 redistribution to a protrusive tip and fibronectin-dependent Rac1 activation. The second component, RCC2, attenuates Rac1 activation outside the protrusive tip by binding to the Rac1 switch regions and competitively inhibiting GEF action, thus preventing off-axial protrusion. Depletion of Coro1C or RCC2 by RNA interference causes loss of cell polarity that results in shunting migration in 1D or 3D culture systems. Furthermore, morpholinos against Coro1C or RCC2, or mutation of any of the binding sites in the Rac1-RCC2-Coro1C complex delays the arrival of neural crest derivatives at the correct location in developing zebrafish, demonstrating the crucial role in migration guidance in vivo.

Syndecan and integrin interactomes: large complexes in small spaces

The syndecan family of transmembrane proteoglycans cooperate with integrins to regulate both early and late events in adhesion formation. The heparan sulphate chains substituted on to the syndecan ectodomains are capable of engaging ligands over great distance, while the protein core spans the plasma membrane and initiates cytoplasmic signals through a short cytoplasmic tail. These properties create a spatial paradox. The volume of the heparan sulphate chains greatly exceeds that of the integrins with which it cooperates, while the short cytodomain must bind to multiple cytoplasmic factors, despite being long enough to bind only one or two. In this review we consider the structural rearrangements that a cell undertakes to overcome spatial restrictions and compare the interactomes of syndecans and integrins to gain insight into the composition of adhesions and how they are regulated over time.

Attenuated stress response to acute restraint and forced swimming stress in arginine vasopressin 1b receptor subtype (Avpr1b) receptor knockout mice and wild-type mice treated with a novel Avpr1b receptor antagonist

Arginine vasopressin (AVP) synthesised in the parvocellular region of the hypothalamic paraventricular nucleus and released into the pituitary portal vessels acts on the 1b receptor subtype (Avpr1b) present in anterior pituitary corticotrophs to modulate the release of adrenocorticotrophic hormone (ACTH). Corticotrophin-releasing hormone is considered the major drive behind ACTH release; however, its action is augmented synergistically by AVP. To determine the extent of vasopressinergic influence in the hypothalamic-pituitary-adrenal axis response to restraint and forced swimming stress, we compared the stress hormone levels [plasma ACTH in both stressors and corticosterone (CORT) in restraint stress only] following acute stress in mutant Avpr1b knockout (KO) mice compared to their wild-type controls following the administration of a novel Avpr1b antagonist. Restraint and forced swimming stress-induced increases in plasma ACTH were significantly diminished in mice lacking a functional Avpr1b and in wild-type mice that had been pre-treated with Avpr1b antagonist. A corresponding decrease in plasma CORT levels was also observed in acute restraint-stressed knockout male mice, and in Avpr1b-antagonist-treated male wild-type mice. By contrast, plasma CORT levels were not reduced in acutely restraint-stressed female knockout animals, or in female wild-type animals pre-treated with Avpr1b antagonist. These results demonstrate that pharmacological antagonism or inactivation of Avpr1b causes a reduction in the hypothalamic-pituitary-adrenal (HPA) axis response, particularly ACTH, to acute restraint and forced swimming stress, and show that Avpr1b knockout mice constitute a model by which to study the contribution of Avpr1b to the HPA axis response to acute stressors.

Localisation of GPR30, a novel G protein-coupled oestrogen receptor, suggests multiple functions in rodent brain and peripheral tissues

Recently, the G protein-coupled receptor GPR30 has been identified as a novel oestrogen receptor (ER). The distribution of the receptor has been thus far mapped only in the rat central nervous system. This study was undertaken to map the distribution of GPR30 in the mouse brain and rodent peripheral tissues. Immunohistochemistry using an antibody against GPR30 revealed high levels of GPR30 immunoreactivity (ir) in the forebrain (e.g. cortex, hypothalamus and hippocampus), specific nuclei of the midbrain (e.g. the pontine nuclei and locus coeruleus) and the trigeminal nuclei and cerebellum Purkinje layer of the hindbrain in the adult mouse brain. In the rat and mouse periphery, GPR30-ir was detected in the anterior, intermediate and neural lobe of the pituitary, adrenal medulla, renal pelvis and ovary. In situ hybridisation histochemistry using GPR30 riboprobes, revealed intense hybridisation signal for GPR30 in the paraventricular nucleus and supraoptic nucleus (SON) of the hypothalamus, anterior and intermediate lobe of the pituitary, adrenal medulla, renal pelvis and ovary of both rat and mouse. Double immunofluorescence revealed GPR30 was present in both oxytocin and vasopressin neurones of the paraventricular nucleus and SON of the rat and mouse brain. The distribution of GPR30 is distinct from the other traditional ERs and offers an additional way in which oestrogen may mediate its effects in numerous brain regions and endocrine systems in the rodent.

Pituitary-adrenal response to acute and repeated mild restraint, forced swim and change in environment stress in arginine vasopressin receptor 1b knockout mice

Arginine vasopressin and corticotrophin-releasing hormone synthesised and released from the hypothalamic paraventricular nucleus are the prime mediators of the hypothalamic-pituitary-adrenal (HPA) axis response to stress. These neurohormones act synergistically to stimulate adrenocorticotophin (ACTH) secretion from the anterior pituitary, culminating in an increase in circulating glucocorticoids. Arginine vasopressin mediates this action at the arginine vasopressin 1b receptor (Avpr1b) located on pituitary corticotrophs. Arginine vasopressin is regarded as a minor ACTH secretagogue in rodents but evidence suggests that it has a role in mediating the neuroendocrine response to some acute and chronic stressors. To investigate the role of the Avpr1b in the HPA axis response to an acute and chronic (repeated) stress, we measured the plasma ACTH and corticosterone concentrations in three stress paradigms in both Avpr1b knockout and wild-type mice. Single acute exposure to restraint, forced swim and change in environment stressors elevated both plasma ACTH and corticosterone concentrations in wild-type animals. Conversely, the ACTH response to the acute stressors was significantly attenuated in Avpr1b knockout mice compared to their wild-type counterparts. Plasma corticosterone concentrations were reduced in Avpr1b knockout mice in response to change in environment but not to mild restraint or forced swim stress. Irrespective of genotype, there was no difference in the plasma ACTH or corticosterone concentrations in response to acute and repeated stressors. The data show that a functional Avpr1b is required for an intact pituitary ACTH response to the acute and chronic stressors used in this study. Furthermore, the normal corticosterone response to repeated exposure to change in environment stress also requires the Avpr1b to drive HPA axis responsiveness.

The role of the arginine vasopressin Avp1b receptor in the acute neuroendocrine action of antidepressants

In times of stress the hypothalamic-pituitary-adrenal (HPA) axis is activated and releases two neurohormones, corticotropin-releasing hormone (Crh) and arginine vasopressin (Avp), to synergistically stimulate the secretion of adrenocorticotropin hormone (ACTH) from the anterior pituitary, culminating in a rise in circulating glucocorticoids. Avp mediates its actions at the Avp V1b receptor (Avpr1b) present on pituitary corticotropes. Dysregulation of the stress response is associated with the pathophysiology of depression and a major treatment involves increasing the availability of monamines at the synaptic cleft. Acute administration of selective serotonin reuptake inhibitors (SSRI) and tricyclic antidepressants (TCA) has previously been shown to activate the HPA axis. The present study was undertaken to evaluate the involvement of the Avpr1b in the HPA axis response to acute SC administration of an SSRI (fluoxetine 10mg/kg) and a TCA (desipramine 10mg/kg). We measured plasma ACTH and corticosterone (CORT) levels and neuropeptide mRNA expression in the hypothalamic paraventricular nucleus (PVN) of Avpr1b knockout (KO) mice and wild-type controls. Fluoxetine and desipramine administration significantly attenuated plasma ACTH and CORT levels in male and female Avpr1b KO mice when compared to their wild-type counterparts. Avp, oxytocin (Oxt) and Crh mRNA expression in the PVN did not change in fluoxetine-treated male Avpr1b KO or wild-type mice. In contrast, fluoxetine treatment increased PVN Avp mRNA levels in female Avpr1b wild type but not KO animals. PVN Oxt mRNA levels increased in fluoxetine-treated female mice of both genotypes. The data suggests that the Avpr1b is required to drive the HPA axis response to acute antidepressant treatment and provides further evidence of a sexual dichotomy in the regulation of PVN Avp/Oxt gene expression following antidepressant administration.

Attenuated stress response to acute lipopolysaccharide challenge and ethanol administration in vasopressin V1b receptor knockout mice

The arginine vasopressin (Avp) 1b receptor (Avpr1b) present on anterior pituitary corticotrophs is involved in the stimulation of adrenocorticotrophic hormone (ACTH) secretion, especially during times of stress. Corticotrophin-releasing hormone (CRH) is considered the major ACTH secretagogue during acute stress whereas Avp appears to be the more dominant mediator of the hypothalamic-pituitary-adrenal (HPA) axis response during chronic stress situations. To investigate the role of the Avpr1b in the HPA axis response to acute stress, we measured ACTH and corticosterone (CORT) plasma levels in Avpr1b knockout (KO) mice and wild-type controls in response to bacterial lipopolysaccharide (LPS) challenge and ethanol (EtOH) administration. Mice deficient in Avpr1b had markedly compromised plasma ACTH and CORT responses to acute (30 min) LPS, but normal ACTH and CORT response to more extended exposure (4 h) to the immune system activator. The plasma ACTH and CORT levels stimulated by intoxicating, sedative doses of EtOH (3.2 and 4 g/kg) were significantly decreased in the Avpr1b KO mice compared to wild-type littermates. Significantly higher EtOH-induced plasma ACTH and CORT secretion was measured in female than in male Avpr1b wild-type mice. There were no differences in the blood alcohol levels following acute EtOH administration in Avpr1b KO or wild-type mice of either gender. Our results clearly suggest that Avpr1b plays a significant role in the HPA axis response to acute immune stress and EtOH intoxication.

Spontaneous IR duplications generated at mitosis in Aspergillus nidulans: further evidence of a preferential site of transposed attachment

A radiation-induced translocation, T(IIR----IIIL), has been shown to be nonreciprocal and to have most of IIR, including its terminus, attached uninverted to the terminus of IIIL.--Progeny with the IIR segment in duplicate, obtained from crosses of T(IIR----IIIL) to strains with a standard genome, were unstable at mitosis; like earlier duplication strains, they suffered deletions from either duplicate segment. Frequent mitotic crossing over occurred between the duplicate IIR segments so that, following deletions, more than two classes of stable, balanced products arose from each heterozygous duplication strain.-- Spontaneous, mitotically arising duplications of the IR segment, bearing the rate-limiting adE20 allele, can be selected on adenine-free medium on which they emerge as vigorous sectors from the stunted adE20 colony. It was shown previously that most such duplications, when selected from a strain with standard genome, had the terminal IR segment attached to the end of IIR. Selection has now been made from an adE20 strain carrying T(IIR----IIIL), and seven of the 13 independent IR duplications were linked to the III-IIR translocation complex. In three strains analyzed further, the duplicate IR segments, which included the IR terminus, were attached uninverted to the terminus of IIR; the segments of IR were of approximately equal genetic length.--This supports earlier suggestions that there is a preferential site for the initiation of IR duplications and a preferential site, the IIR terminus, for their attachment.

Spontaneous duplications and transpositions of a large chromosome segment in Aspergillus nidulans

Spontaneous revertants of the leaky adE20 mutant of Aspergillus nidulans were obtained as vigorous sectors emerging from stunted colonies on adenine-free medium. Among the genetically heterogeneous sectors up to about 20% were recognized unequivocally as having an additional chromosome segment bearing adE20; two doses of this leaky allele permitted growth without added adenine. Eleven spontaneous duplication strains of independent origin were analysed genetically. Eight carried the duplicate segment on chromosome IIR; three of these, phenotypically similar to all eight, were analysed in detail and were shown-within the limits of such genetic analysis - to have a large, terminal segment of IR duplicated and attached terminally and uninverted to IIR. One strain had a duplication, possibly tandem, on IR and two had duplications attached elsewhere in the genome. The results suggested a preferential site for the initiation of duplicate segments in this system, as well as a preferential site for their attachment. Agents known to modify instability of a previously studied Dp(IR----IIR) strain affected the frequency of duplications among selected adE20 revertant sectors and/or the genomic locations of duplicated segments. Trypan blue and coumarin, which enhance Dp(IR----IIR) instability in a specific way, and Co2+, which stabilizes Dp(IR----IIR), gave 14, 50 and 62% duplication sectors respectively, among revertants. Duplications selected in the presence of Co2+ had mainly IIR attachments; of those from trypan blue and coumarin, about one-quarter were attached to IIL and none to IIR.

Modification of chromosome instability in Aspergillus nidulans

Strains of Aspergillus nidulans with a chromosome segment in duplicate show instability at mitosis; their colonies produce faster-growing sectors which arise from nuclei with spontaneous deletions in either duplicate segment. In an attempt to probe the deletion process, the effects of mutations causing sensitivity to UV treatment, and those of manganous ions, have been studied in strains carrying either Dp(I,II) or Dp(III,VIII). For comparison, the effects of Mn2+ on balanced and unbalanced diploids have also been examined. The uvsE allele, which decreases intragenic mitotic crossing over in diploids, increased deletion frequency in strains with either duplication. The uvsB allele, which increases intragenic mitotic crossing over in diploids, increased deletion frequency only in Dp(I,II) strains; in addition, by causing early mitotic crossing over between the homologous segments, it produced some novel deletion products. Mn2+ substantially decreased the deletion frequency in Dp(I,II) strains and decreased mitotic crossing over in diploids; it had no effect on Dp(III,VIII) strains. The results suggest that in haploid duplication strains there are two classes of spontaneous DNA lesions, recombinogenic and non-recombinogenic, both of which, failing repair, lead to deletion.

Mitotic processes which restore genome balance in Aspergillus nidulans

Previous work had shown that haploid strains of Aspergillus nidulans with a duplicate chromosome segment (one in normal position, one translocated to another chromosome) were unstable at mitosis; genome balance was restored by spontaneous deletion of either duplicate segment. Diploids with an extra, translocated segment showed high instability which was confined to the excess segments; loss of one of these, usually that in translocated position, gave balanced diploid nuclei and the loss was assumed to be by deletion. This led to the proposal that high-frequency deletion was provoked by, and confined to, the excess segment. In the present work it has been shown that elimination of the translocated segment in such diploids occurs more frequently by mitotic crossing over than by deletion. Accordingly, in a more rigorous test of the possible association of excess segments and deletions, a diploid homozygous for an extra, translocated segment has been studied as mitotic crossing over in this strain could not give a balanced genome. The strain was extremely unstable and gave variants of which most had a balanced, or near-balanced, diploid genome. Some variants arose by simultaneous deletions involving both non-translocated segments; almost all variants had deletions with breakpoints different from those most frequent in the corresponding, duplication haploid. The results have shown the diversity of mechanisms available for the correction of genome imbalance and that, at least in the case of Dp(I,II), the degree and modalities of mitotic instability are functions of the balance of chromosome segments and of ploidy.

Photophysical properties of zinc and magnesium tris(pyrochlorophyllide a) 1,1,1-tris(hydroxymethyl)ethane triesters

The zinc and magnesium tris(pyrochlorophyllide a) 1,1,1-tris(hydroxymethyl)ethane triesters have properties that are very similar to those exhibited by pairs of pyrochlorophyll a or chlorophyll a linked by ethylene glycol through their propionic acid side chains. In the open configuration, the fluorescence lifetimes and emission spectra of the triesters resemble those of chlorophyll a monomers. However, the triesters have a mechanism for energy dissipation not present in monomeric chlorophyll a, which prevents the build-up of significant concentrations of molecules in S(1) states. Optical pumping of these compounds in their folded configuration results in the formation of high concentrations of molecules in S(1) states and in laser light emission, which originates from the two folded macrocycles. The optical data indicate that efficient energy transfer occurs from the open to the folded configurations.

The effects of coumarin on the frequency of deletions in a duplication strain of Aspergillus nidulans

Strains of A. nidulans with a chromosome segment in duplicate show instability resulting from deletions in either of the duplicate segments. In Dp (I, II) strains, with the terminal segment of IR attached terminally to IIR, spontaneous deletions occur most frequently, though not exclusively, from the translocated segment. Coumarin, at concentrations which did not affect viability viability or growth rate, enhanced the instability of Dp (I, II) strains by selectively increasing only the deletion class of highest spontaneous frequency. This selective action is interpreted tentatively as due to inhibition of the repair of a particular class of DNA lesion occurring spontaneously in the attachment region of Dp (I, II) strains.

Genetic control of chromosome instability in Aspergillus nidulans as a mean for gene amplification in eukaryotic microorganisms

A haploid strain of Aspergillus nidulans carrying I-II duplication homozygous for the leaky mutation adE20 shows impreved growth on minimal medium. The duplication, though more stable than disomics, still shows instability. Several methods were used for detecting genetic control of improved stability. (a) visual selection, using a duplicated strain which is very unstable due to UV sensitivity, (adE20, biAl/dp yA2; uvsB). One stable strain showed a deletion (or a lethal mutation?) DISTAL TO BIA on the segment at the original position (on chromosome I). This deletion reduces crossing over frequency between the two homologous segments. As the deletion of the non-translocated segment (yelow sectors) must be preceded by crossing over, the above reduces the frequency of yellow sectors. A deletion of the translocated segment (green sectors) results in non-viability due to the deletion, and such sectors do not appear. The net result is a stable duplication involving only 12 C.O. units carrying the gene in concern. (b) Suppressors of UV sensitivity (su-uvsB) were attempted using the above uvs duplicated strain. Phenotypic revertants were easily obtained, but all were back mutations at the uvsB locus. (c) Mutations for UV resistance higher than that of the wild type were not obtained, in spite of the strong selective pressure inserted. (d) Recombination deficient mutations (rec), six altogether, all uvs+, did not have any effect on stability.

Mitotic non-conformity in Aspergillus: successive and transposable genetic changes

Strains ofAspergillus nidulanswith, a duplicate chromosome segment are mitotically unstable; in addition to phenotypically improved variants, arising following deletions in either duplicate segment, they give morphologically deteriorated types, some with, enhanced stability. In one isolate, deterioration and increased instability were determined by mutation in a duplicate segment; a more stable derivative no longer had this mutation but had one in another linkage group. Another variant, too unstable for analysis, gave derivatives whose single, new mutations were in different linkage groups. It is proposed that deterioration and increased instability result from tandem duplications on either duplicate segment; transposition of these to non-duplicated regions reduces instability. Another 17 variants had a single new mutation each; mutations, possibly clustered, occurred in all linkage groups. In these strains perhaps transposition preceded analysis. Deteriorated variants gave lineages of types with morphological changes caused by further, superimposed mutations. This continued instability is explained as interaction, in fidelity of replication, of non-homologous chromosome segments.

Instability inA. nidulansstems from chromosome imbalance. As imbalance is known or suspected in other cases of instability it may be possible to show common mechanisms for apparently diverse phenomena.

Mitotic non-conformity in Aspergillus nidulans: the production of hypodiploid and hypohaploid nuclei

Strains ofAspergillus nidulanswith a chromosome segment additional to the normal complement are vegetatively unstable. Previous work suggested that the deletions occurring at mitosis were confined to the unbalanced segments. It has been shown now that deletions, while probably always involving a duplicate segment, may extend beyond it to produce hypohaploids and hypodiploids, respectively, from unbalanced haploid and unbalanced diploid parents.

Hypoploids have been proposed tentatively as an explanation for some cases of phenotypic variegation; on this basis it is possible to account for some of the diverse phenomena shown by, for example, position-effect variegation.

A system generating spontaneous intrachromosomal changes at mitosis in Aspergillus nidulans

Previous studies had shown that haploid strains ofAspergillus nidulanswhich have a chromosome segment in duplicate are unstable at mitosis. Through the study of various haploid and diploid strains, with and without translocations and with balanced and unbalanced genomes, it has been shown: (1) that imbalance of chromosome segments is responsible for instability, and (2) that the chromosomal deletions produced are confined solely or largely to the segments which provoke instability.

The term ‘mitotic non-conformity’ has been proposed for this instability phenomenon. An explanation for it has been sought in terms of attachment sites, limited in number and specific for chromosome segments, at which replication is initiated.

Studies on the inhibition and mutation of Aspergillus nidulans by acridines

A number of acridines have been tested for ability to inhibit conidia of strains ofAspergillus nidulans. The effectiveness of any one acridine in growth inhibition and killing involves interaction of genotype and conditions of treatment such as temperature, pH, treatment medium and light intensity. Mutant alleles which confer growth resistance to acriflavine are selective in their actions towards other acridines, may differ in their dominance relationships with different acridines and are even selective with regard to the conditions under which they confer acriflavine resistance. Certain pairs of acridines, used simultaneously, show additive effects, potentiation, or annulment by one of inhibition caused by the other.

Some of these findings have been applied in a study of factors affecting acridine-induced mutation inAspergillusconidia. Under conditions which permit metabolism, acriflavine induces a high frequency of unstable morphological variants. One such variant has been shown to be a disomic. Using a system of reversion from auxotrophy to prototrophy, acriflavine-induced mutation has been obtained both with high light intensities and in the absence of light. In the latter case recombination as a feature of the mutation process is excluded.