Aryl hydrocarbon receptor agonists trigger avoidance of novel food in rats

The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that mediates the toxicity of dioxins, but also plays important physiological roles, which are only beginning to unfold. Previous studies have surprisingly unveiled that low doses of the potent AHR agonist TCDD induce a strong and persistent avoidance of novel food items in rats. Here, we further examined the involvement of the AHR in the avoidance response in Sprague-Dawley rats with three established AHRagonists: 6-formylindolo(3,2-b)carbazole (FICZ), (beta-naphthoflavone (BNF) and benzo[a]pyrene (BaP); with a novel selective AHR modulator (C2); and with an activator of another nuclear receptor, CAR: 2,4,6-tryphenyldioxane-1,3 (TPD). As sensitive indices of AHR or CAR activity, we used Cypl al and Cyp2b1 gene expression, as they are, respectively, the drug-metabolizing enzymes specifically regulated by them. We further attempted to address the roles played by enhanced neophobia and conditioned taste aversion (CTA) in the avoidance behaviour. All AHR agonists triggered practically total avoidance of novel chocolate, but the durations varied. Likewise, acutely subtoxic doses of C2, differing by 25-fold, all elicited a similar outcome. In contrast, TPD did not influence chocolate consumption at all. If rats were initially accustomed to chocolate for 6 h after single FICZ or BNF exposure, avoidance was still clearly present two weeks later when chocolate was offered again. Hence, the avoidance response appears to specifically involve the AHR instead of being triggered by induction of intestinal or hepatic nuclear receptor signalling in general. It is also shared by both endogenous and exogenous AHR activators. Moreover, this behavioural change in rats seems to contain elements of both CTA and enhanced neophobia, but further clarification of this is still required. (C) 2016 Elsevier Inc. All rights reserved.Peer reviewe

Exploring the toxicological and physiological functions of the AH receptor : Selective modulation by two novel compounds and involvement in novel food avoidance behaviour

The aim of this thesis study was to gain more information on the physiological and toxicological functions of the aryl hydrocarbon receptor (AHR). The effects of two novel selective AHR modulators (SAHRMs) were investigated in vitro and in vivo. In addition, the involvement of the AHR in the avoidance of novel food was examined. The AHR is an evolutionarily ancient, apparently over 600-million-year-old protein. It is a ligand-activated transcription factor that modulates the expression of various genes within cells. One of the most studied groups of compounds that activate the AHR are dioxins. They are environmental contaminants primarily formed as by-products of various industrial processes, and many of them are toxic. Dioxins are chemically very persistent and lipid soluble, and thus accumulate in the food chain. Therefore, humans are also exposed to small amounts from food. In Finland, the most common source of dioxins is fatty wild fish from the Baltic Sea. The AHR has been recognised as the mediator of dioxin-induced toxicity for decades. More recently, it has also been shown to be involved in several physiological functions of the body, including the regulation of reproduction, foetal development, the immune system and autoimmunity. However, our understanding of the mechanisms of both the toxicological and physiological functions of the AHR remains incomplete. As a consequence, for instance, human health risk assessment of dioxins is challenging. Furthermore, better understanding of the physiological effects of the AHR could help elucidate the aetiology and pathogenesis of certain diseases, and therefore also benefit the discovery of novel pharmacological therapies. As lead compounds for drug discovery, SAHRMs are particularly interesting. They only elicit subsets of AHR-mediated effects, often without the major toxic outcomes of dioxins. Moreover, they could be valuable tools in elucidating the so far incompetently understood, multifaceted physiological roles of AHR, and the underlying molecular mechanisms. This thesis research had two main objectives. The first was related to studying the in vitro and in vivo toxicity of two novel SAHRMs, which are intended as drug compounds for the treatment of autoimmune diseases. The aim was to determine whether they appear suitable for pharmacological use from the pre-clinical safety perspective. Furthermore, finding out the extent to which their effects resemble or differ from those of the most toxic dioxin, TCDD, was of interest. The second objective was to accumulate more knowledge on a peculiar novel food avoidance behaviour, previously characterised in rats and mice after exposure to TCDD. This behaviour resembles a recognised behaviour model, conditioned taste aversion (CTA), which is also exhibited in humans, for instance in conjunction with nausea related to cancer treatment. The aim here was to verify whether the aforementioned rodent response is a physiological effect of the AHR or, more specifically, a consequence of TCDD exposure. Based on the results, the novel SAHRMs are very effective AHR activators, both in vitro and in vivo, and are in fact comparable to TCDD. However, their toxicity profiles are distinct from that of TCDD, and they appear considerably less toxic in rats. Therefore, the novel SAHRMs appear promising as possible drug compounds, and also highly interesting as tools for AHR research. Despite the differences in toxicity, one of the novel SAHRMs, as well as all of the three other AHR activators tested in this study, induced a strong avoidance response resembling that previously observed to TCDD, but shorter lasting. In addition, the reaction was not inducible in AHR knock-out rats. Thus, this study confirmed that the novel food avoidance behaviour is mediated by the AHR. The effect appears protective against potentially harmful ingested foods, and is therefore another physiological function of the AHR.Tämän väitöskirjatutkimuksen tarkoituksena oli saada lisätietoa aryylihiilivetyreseptorin (AHR) fysiologisista vaikutuksista elimistössä sekä sen kautta välittyvän toksisuuden mekanismeista. Tutkimme kahden uuden, valikoivasti AHR:n toimintaa säätelevän lääkeainekandidaatin vaikutuksia. Lisäksi tarkastelimme AHR:n osallisuutta aiemmin kuvatussa, uusien ruoka-aineiden karttamisreaktiossa. AHR on evolutiivisesti muinainen, ilmeisesti yli 600 miljoonaa vuotta vanha proteiini, joka säätelee soluissa lukuisten geenien ilmentymistä. Yksi eniten tutkituista AHR:n toimintaa aktivoivista aineryhmistä on dioksiinit. Ne ovat ympäristölle ja terveydelle haitallisia yhdisteitä, joita syntyy pääasiassa lämpö- ja teollisuusprosessien sivutuotteina. Koska ne ovat kemiallisesti erittäin pysyviä ja hyvin rasvaliukoisia, ne kertyvät ravintoketjuissa, ja siten myös ihmiset altistuvat niille ravinnon välityksellä. Suomessa tavallisin dioksiinien lähde on Itämeren rasvainen villikala. AHR on tunnettu dioksiinien aiheuttamien myrkyllisten vaikutusten välittäjänä jo pitkään. Sittemmin sillä on osoitettu olevan myös lukuisia elimistön normaalin toiminnan kannalta tärkeitä fysiologisia tehtäviä, muun muassa lisääntymisen säätelyssä, yksilönkehityksessä, autoimmuniteetissa ja immuunipuolustuksessa. Fysiologisten tehtävien, samoin kuin AHR:n välittämien toksisten vaikutusten mekanismien tuntemus on kuitenkin toistaiseksi puutteellista, mikä muun muassa vaikeuttaa dioksiinien ihmisille aiheuttamien terveysriskien arviointia. AHR:n fysiologisten vaikutusten parempi tuntemus voisi lisäksi auttaa tiettyjen sairauksien syntymekanismien selvittämisessä ja siten edistää uusien lääkehoitojen kehitystä. Selektiivisesti AHR:n toimintaa säätelevät aineet ovat lääkekehityksen kannalta erityisen kiinnostavia, sillä monet niistä aktivoivat AHR:ää aiheuttamatta dioksiineille tyypillisiä haittavaikutuksia. Lisäksi ne voivat olla hyödyllisiä työkaluja AHR:n fysiologisten vaikutusten tutkimisessa. Tällä väitöskirjatutkimuksella oli kaksi päätavoitetta. Ensimmäinen liittyi kahden uuden, AHR:ää valikoivasti aktivoivan lääkeainekandidaatin toksikologisten vaikutusten tutkimiseen. Tarkoituksena oli selvittää, vaikuttavatko ne toksisuusprofiilinsa puolesta sopivilta lääkeaineiksi, jolloin niitä voitaisiin edelleen kehittää esimerkiksi autoimmuunisairauksien hoitoon. Lisäksi olimme kiinnostuneita selvittämään, missä määrin näiden aineiden aiheuttamat vaikutukset muistuttavat tai poikkeavat myrkyllisimmän dioksiinin, TCDD:n, aiheuttamista vaikutuksista. Toisena tavoitteena oli syventää tietoa aiemmin rotilla ja hiirillä TCDD-annostelun jälkeen havaitusta uusien ruoka-aineiden karttamisreaktiosta, joka muistuttaa ennestään tunnettua käyttäytymismallia, ehdollistettua makuaversiota (CTA). Samankaltainen makuaversio tunnetaan myös ihmisillä muun muassa syövän hoitoon liittyvän pahoinvoinnin yhteydessä. Halusimme varmistaa, johtuuko edellä mainittu jyrsijöiden reaktio yleisesti AHR-aktivaatiosta vai onko se ainoastaan TCDD:lle ominainen vaikutus. Tulosten perusteella edellä mainitut uudet, selektiiviset AHR-modulaattorit ovat tehokkaita, TCDD:n veroisia AHR-aktivaattoreita. Toksisuusprofiililtaan ne ovat kuitenkin olennaisesti TCDD:tä haitattomampia ja vaikuttavat siten kiinnostavilta lääkeainekandidaateilta. Havaituista eroista huolimatta sekä toinen niistä että muut tässä työssä testatut AHR-aktivaattorit aiheuttivat TCDD:n tavoin voimakkaan, joskin lyhytkestoisemman, uusien ruoka-aineiden karttamisreaktion. Lisäksi reaktio puuttui AHR-poistogeenisiltä rotilta. Tulos vahvistaa, että tämä mielenkiintoinen vaikutus on AHR-välitteinen. Tämä käyttäytymismuutos suojaa ilmeisesti eliöitä haitalliselta vaikuttavan ravinnon nauttimiselta ja on siten uusi AHR:n fysiologinen vaikutus.

Transcriptomic Impact of IMA-08401, a Novel AHR Agonist Resembling Laquinimod, on Rat Liver

IMA-08401 (C2) is a novel aryl hydrocarbon receptor (AHR) agonist and selective AHR modulator (SAHRM) that is structurally similar to laquinimod (LAQ). Both compounds are converted to the AHR-active metabolite DELAQ (IMA-06201) in vivo. SAHRMs have been proposed as therapeutic options for various autoimmune disorders. Clinical trials on LAQ have not reported any significant toxic outcomes and C2 has shown low toxicity in rats; however, their functional resemblance to the highly toxic AHR agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) raises questions. Here, we characterize the hepatic transcriptomic changes induced by acute (single-dose) and subacute exposure (repeated dosing for 5 days followed by a 5-day recovery period) to C2 in Sprague-Dawley rats. Exposure to C2 leads to activation of the AHR, as shown by altered transcription of Cyp1a1. We identify a heightened response early after exposure that drops off by day 10. Acute exposure to C2 leads to changes to transcription of genes involved in antiviral and antibacterial responses, which highlights the immunomodulator effects of this AHR agonist. Subacute exposure causes an oxidative stress response in the liver, the consequences of which require further study on target tissues such as the CNS and immune system, both of which may be compromised in this patient population

Existence of solutions for higher order ϕ−\phi-Laplacian BVPs on the half-line using a one-sided Nagumo condition with nonordered upper and lower solutions

In this paper, we consider the following $(n+1)$st order bvp on the half line with a $\phi-$Laplacian operator $$\begin{cases} (\phi(u^{(n)}))'(t)=f(t,u(t),\ldots,u^{(n)}(t)),& a.e., \,t\in [ 0,+\infty ),\\& n\in \mathbb{N}\setminus\{0\}, \\ u^{(i)}(0)=A_{i},\, i=0,\ldots,n-2,\\ u^{(n-1)}(0)+au^{(n)}(0)=B,\\ u^{(n)}(+\infty )=C. \end{cases}$$ The existence of solutions is obtained by applying Schaefer's fixed point theorem under a one-sided Nagumo condition with nonordered lower and upper solutions method where $f$ is a $L^{1}$-Carath\'eodory function

In vitro toxicity and in silico docking analysis of two novel selective AH-receptor modulators

The mediator of dioxin toxicity, aryl hydrocarbon receptor (AHR), has also important physiological functions. Selective AHR modulators (SAHRMs) share some effects of dioxins, except for their marked toxicity. We recently characterised toxicologically two novel SAHRMs, prodrugs IMA-08401 and IMA-07101 in rats, demonstrating that they are far less deleterious than the most toxic AHR-agonist, TCDD. Here, we analysed the in vitro toxicity and in silico AHR binding of the respective active, deacetylated metabolites, IMA-06201 (N-ethyl-N-phenyl-5-chloro-1,2-dihydro-4-hydroxy-1-methyl-2-oxo-quinoline-3-carboxamide) and IMA-06504 (N-(4-trifluoromethylphenyl)-1,2-dihydro-4-hydroxy-5-methoxy-1-methyl-2-oxo-quinoline-3-carboxamide). In H4IIE rat hepatoma cells, IMA-06201 and IMA-06504 induced CYP1A1 with comparable potencies and efficacies to those of TCDD. They had little effect on cell viability as assessed by LDH leakage and MTT reduction assays, and were not mutagenic in the Ames test, but IMA-06504 elicited a maximally 2.7-fold increase in micronuclei. Molecular docking simulations showed that similar to TCDD, they occupy the central region of AHR ligand binding cavity. Hence, while showing low to negligible in vitro toxicity, these novel SAHRMs bind to the AHR qualitatively in a similar fashion to TCDD, and appear comparably powerful AHR agonists. Combined with our earlier results demonstrating that they seem considerably less toxic in vivo than TCDD, these compounds are thus highly interesting new SAHRMs.Peer reviewe

Toxicological characterisation of two novel selective aryl hydrocarbon receptor modulators in Sprague-Dawley rats

The aryl hydrocarbon receptor (AHR) mediates the toxicity of dioxins, but also plays important physiological roles. Selective AHR modulators, which elicit some effects imparted by this receptor without causing the marked toxicity of dioxins, are presently under intense scrutiny. Two novel such compounds are IMA-08401 (N-acetyl-N-phenyl-4-acetoxy-5-chloro-1,2-dihydro-1-methyl-2-oxo-quinoline-3-carboxamide) and IMA-07101 (N-acetyl-N-(4-trifluoromethylphenyl)-4-acetoxy-1,2-dihydro-5-methoxy-1-methyl-2-oxo-quinoline-3-carboxamide). They represent, as diacetyl prodrugs, AHR-active metabolites of the drug compounds laquinimod and tasquinimod, respectively, which are intended for the treatment of autoimmune diseases and cancer. Here, we toxicologically assessed the novel compounds in Sprague-Dawley rats, after a single dose (8.75-92.5 mg/kg) and 5-day repeated dosing at the highest doses achievable (IMA-08401: 100 mg/kg/day; and IMA-07101: 75 mg/kg/day). There were no overt clinical signs of toxicity, but body weight gain was marginally retarded, and the treatments induced minimal hepatic extramedullary haematopoiesis. Further, both the absolute and relative weights of the thymus were significantly decreased. Cyp1a1 gene expression was substantially increased in all tissues examined. The hepatic induction profile of other AHR battery genes was distinct from that caused by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The only marked alterations in serum clinical chemistry variables were a reduction in triglycerides and an increase in 3-hydroxybutyrate. Liver and kidney retinol and retinyl palmitate concentrations were affected largely in the same manner as reported for TCDD. In vitro, the novel compounds activated CYP1A1 effectively in H4IIE cells. Altogether, these novel compounds appear to act as potent activators of the AHR, but lack some major characteristic toxicities of dioxins. They therefore represent promising new selective AHR modulators. (C) 2017 Elsevier Inc. All rights reserved.Peer reviewe

Teolliset mineraalikuidut toimistotyyppisissä työtiloissa : Esiintyminen, altistumisen arviointi, terveysvaikutukset ja päästöjen hallinta

Tämä katsaus on laadittu Kansallisen sisäilma ja terveys -ohjelman rahoituksella osana Terveet tilat 2028 -hanketta. Työterveyslaitoksen asiantuntijat laativat katsauksen vuonna 2019 liittyen ohjelman osa-alueeseen 2: rakennusten ongelmatilanteet. Tavoitteena oli arvioida teollisten mineraalikuitujen merkitystä toimistotyyppisten tilojen sisäilmassa. Katsauksen tuloksia hyödynnetään myöhemmin mm. altistumisolosuhteiden arvioimiseen liittyvien ohjeiden päivityksissä. Tämä katsaus sisältää teollisiin mineraalikuituihin liittyvän kirjallisuuskoosteen, toksikologista ja epidemiologista arviointia sekä pitoisuustasojen tarkastelua työympäristöissä, pääpainona toimistotyyppiset työpaikat. Katsauksessa arvioidaan toimistotyyppisten työympäristöjen kuitulähteitä ja niihin liittyviä teollisten mineraalikuitujen pitoisuuksia, sekä niiden mahdollista yhteyttä koettuihin ja todettuihin terveyshaittoihin sekä kuitupäästöjen hallintakeinoja. Lisäksi kartoitettiin mittausmenetelmiä ja laadittiin suositukset niiden päivittämiseksi

First report of Colletotrichum gloeosporioides on citrus in Algeria

Wither-tip symptoms of twigs were observed on cultivated sweet orange and lemon trees in Algeria. The causal agent was identified as Colletotrichum gloeosporioides on the basis of cultural and morphological features. The identification of the fungus was confirmed by sequencing of the internal transcribed spacer region of rDNA. Pathogenicity tests revealed that C. gloeosporioides isolated from withered twigs caused typical anthracnose symptoms on orange leaves. This is the first report on Colletotrichum gloeosporioides as causal agent of anthracnose in Citrus trees in Algeria