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Midbrain dopamine neurons deteriorate in Parkinson's disease (PD) that is a progressive neurodegenerative movement disorder. No cure is available that would stop the dopaminergic decline or restore function of injured neurons in PD. Neurotrophic factors (NTFs), e.g., glial cell line-derived neurotrophic factor (GDNF) are small, secreted proteins that promote neuron survival during mammalian development and regulate adult neuronal plasticity, and they are studied as potential therapeutic agents for the treatment of neurodegenerative diseases. However, results from clinical trials of GDNF and related NTF neurturin (NRTN) in PD have been modest so far. In this review, we focus on cerebral dopamine neurotrophic factor (CDNF), an unconventional neurotrophic protein. CDNF delivered to the brain parenchyma protects and restores dopamine neurons in animal models of PD. In a recent Phase I-II clinical trial CDNF was found safe and well tolerated. CDNF deletion in mice led to age-dependent functional changes in the brain dopaminergic system and loss of enteric neurons resulting in slower gastrointestinal motility. These defects in Cdnf(-/-) mice intriguingly resemble deficiencies observed in early stage PD. Different from classical NTFs, CDNF can function both as an extracellular trophic factor and as an intracellular, endoplasmic reticulum (ER) luminal protein that protects neurons and other cell types against ER stress. Similarly to the homologous mesencephalic astrocyte-derived neurotrophic factor (MANF), CDNF is able to regulate ER stress-induced unfolded protein response (UPR) signaling and promote protein homeostasis in the ER. Since ER stress is thought to be one of the pathophysiological mechanisms contributing to the dopaminergic degeneration in PD, CDNF, and its small-molecule derivatives that are under development may provide useful tools for experimental medicine and future therapies for the treatment of PD and other neurodegenerative protein-misfolding diseases.

When adolescents with ADHD enter adulthood, some no longer meet disorder diagnostic criteria but it is unknown if biological and cognitive abnorma lities persist. We tested the hypothesis that people diagnosed with ADHD during adolescence present residual brain abnormalities both in brain structure and in working memory brain function. 83 young adults (aged 20-24 years) from the Northern Finland 1986 Birth Cohort were classified as diagnosed with ADHD in adolescence (adolescence ADHD, n = 49) or a control group (n = 34). Only one patient had received medication for ADHD. T1-weighted brain scans were acquired and processed in a voxel-based analysis using permutation-based statistics. A sub-sample of both groups (ADHD, n = 21; controls n = 23) also performed a Sternberg working memory task whilst acquiring fMRI data. Areas of structural difference were used as a region of interest to evaluate the implications that structural abnormalities found in the ADHD group might have on working memory function. There was lower grey matter volume bilaterally in adolescence ADHD participants in the caudate (p < 0.05 FWE corrected across the whole brain) at age 20-24. Working memory was poorer in adolescence ADHD participants, with associated failure to show normal load-dependent caudate activation. Young adults diagnosed with ADHD in adolescence have structural and functional deficits in the caudate associated with abnormal working memory function. These findings are not secondary to stimulant treatment, and emphasise the importance of taking a wider perspective on ADHD outcomes than simply whether or not a particular patient meets diagnostic criteria at any given point in time.

Neurotrophic factors (NTFs) are secreted proteins which promote the survival of neurons, formation and maintenance of neuronal contacts and regulate synaptic plasticity. NTFs are also potential drug candidates for the treatment of neurodegenerative diseases. Parkinson’s disease (PD) is mainly caused by the degeneration of midbrain dopaminergic neurons. Current therapies for PD do not stop the neurodegeneration or repair the affected neurons. Thus, search of novel neurotrophic factors for midbrain dopaminergic neurons, which could also be used as therapeutic proteins, is highly warranted. In the present study, we identified and characterized a novel protein named conserved dopamine neurotrophic factor (CDNF), a homologous protein to mesencephalic astrocyte-derived neurotrophic factor (MANF). Others have shown that MANF supports the survival of embryonic midbrain dopaminergic neurons in vitro, and protects cultured cells against endoplasmic reticulum (ER) stress. CDNF and MANF form a novel evolutionary conserved protein family with characteristic eight conserved cysteine residues in their primary structure. The vertebrates have CDNF and MANF encoding genes, whereas the invertebrates, including Drosophila and Caenorhabditis have a single homologous CDNF/MANF gene. In this study we show that CDNF and MANF are secreted proteins. They are widely expressed in the mammalian brain, including the midbrain and striatum, and in several non-neuronal tissues. We expressed and purified recombinant human CDNF and MANF proteins, and tested the neurotrophic activity of CDNF on midbrain dopaminergic neurons using a 6-hydroxydopamine (6-OHDA) rat model of PD. In this model, a single intrastriatal injection of CDNF protected midbrain dopaminergic neurons and striatal dopaminergic fibers from the 6-OHDA toxicity. Importantly, an intrastriatal injection of CDNF also restored the functional activity of the nigrostriatal dopaminergic system when given after the striatal 6-OHDA lesion. Thus, our study shows that CDNF is a potential novel therapeutic protein for the treatment of PD. In order to elucidate the molecular mechanisms of CDNF and MANF activity, we resolved their crystal structure. CDNF and MANF proteins have two domains; an amino (N)-terminal saposin-like domain and a presumably unfolded carboxy (C)-terminal domain. The saposin-like domain, which is formed by five α-helices and stabilized by three intradomain disulphide bridges, may bind to lipids or membranes. The C-terminal domain contains an internal cysteine bridge in a CXXC motif similar to that of thiol/disulphide oxidoreductases and isomerases, and may thus facilitate protein folding in the ER. Our studies suggest that CDNF and MANF are novel potential therapeutic proteins for the treatment of neurodegenerative diseases. Future studies will reveal the neurotrophic and cytoprotective mechanisms of CDNF and MANF in more detail. Hermokasvutekijät ovat solun erittämiä proteiineja, jotka edistävät neuronien eloonjäämistä, kontaktien muodostumista ja säätelevät hermosolujen toimintaa. Edullisten ominaisuuksien vuoksi hermokasvutekijöitä on tutkittu mahdollisina lääkkeinä hermoston rappeumasairauksiin. Parkinsonin tauti on etenevä liikesairaus, jossa keskiaivojen mustatumakkeen dopamiinineuronit vähitellen tuhoutuvat. Tautiin ei ole olemassa hoitoa, joka pysäyttäisi neuronien tuhoutumisen tai edistäisi niiden toiminnan palautumista. Ryhmämme tutkii hermokasvutekijöitä, joista voisi olla hyötyä myös hermoston rappeumatautien hoidossa tulevaisuudessa. Tässä työssä kuvattiin uusi conserved dopamine neurotrophic factor (CDNF)-proteiini, joka on läheistä sukua aiemmin kuvatulle MANF-proteiinille. Selkärankaisten CDNF ja MANF, sekä selkärangattomien eläinten, kuten banaanikärpäsen ja sukkulamadon MANF muodostavat evoluutiossa varhain syntyneen proteiiniperheen. Osoitimme, että nisäkkäiden CDNF ja MANF ovat solusta erittyviä proteiineja, jotka ilmentyvät laajasti aivokudoksessa. Ne ilmentyvät paitsi keskiaivoissa, myös muissa aivojen osissa ja useissa hermoston ulkopuolisissa kudoksissa. Työssä tuotimme CDNF-proteiinia ja testasimme sen vaikutusta kokeellisessa Parkinsonin taudin mallissa rotilla. Rotille aiheutettiin 6-hydroksidopamiini (6-OHDA)-toksiinilla Parkinsonin tautia muistuttava vaurio. Osoitimme, että CDNF estää dopamiinineuronien tuhoutumisen, kun CDNF injisoidaan rotan aivoihin ennen toksiinia. Toisessa koesarjassa, jossa CDNF injisoitiin aivoihin neljä viikkoa toksiinivaurion jälkeen, CDNF korjasi dopamiinineuronien toimintaa ja rottien liikehäiriötä. Jälkimmäinen koeasetelma muistuttaa tilannetta Parkinson-potilailla, kun jo olemassa olevaa vauriota pyritään korjaamaan lääkehoidolla. Kokeiden perusteella CDNF saattaa olla hyödyllinen Parkinsonin taudin hoidossa. Työssä selvitimme myös CDNF- ja MANF-proteiinien molekyylirakenteen, josta on apua tutkittaessa näiden proteiinien toimintamekanismeja solussa. Rakenteen perusteella saatiin selville, että CDNF ja MANF sitoutuvat lipideihin ja mahdollisesti solumembraaneihin. CDNF:n neurotroofinen vaikutus saattaa välittyä soluun membraani-interaktion kautta. Rakenne sisältää myös rikkisillan, jonka kaltainen löytyy tietyiltä solun endoplasmisessa retikulumissa (ER:ssa) toimivilta entsyymeiltä, jotka auttavat proteiineja laskostumaan oikein. Tämä tukee muiden tutkimusryhmien raportteja, joissa osoitetaan MANF-proteiinin edistävän viljeltyjen solujen eloonjäämistä stressitilanteissa kun ER:n toiminta ja proteiinieritys ovat häiriintyneet. Rakennemallin perusteella CDNF ja MANF saattavat edistää proteiinien laskostumista ER:ssa, ja näin suojata soluja stressitilanteissa. Tutkimuksen perusteella CDNF ja MANF saattavat olla hyödyllisiä neurodegeneratiivisten sairauksien hoidossa. Jatkotutkimuksin on tarkoitus selvittää millaiset molekyylimekanismit toimivat CDNF/MANF-proteiinien soluja suojaavan ja solujen toimintaa edistävän aktiivisuuden taustalla.

Number of heterozygous pupae in the rescue experiments of DmManf Δ96 mutant lethality by abolishment of debcl. A pdf file. (PDF 29 kb)

Number of heterozygous pupae in the rescue experiments of DmManf Δ96 mutant lethality by abolishment of debcl. A pdf file. (PDF 29 kb)