Serotonin Transmission in Mental Disorders
As always, Greengard makes outstanding contributions. Very, very interesting.

We, as well as several other groups, have demonstrated peptide increases in schizophrenia (Hole et al., 1979; Drysdale et al., 1982; Idei et al., 1982; Cade et al., 2000) and also in several other disorders (e.g., Cade et al., 2000; Reichelt and Knivsberg, 2003). This confirms older data from Sweden (Lindstrom et al., 1986), where opioids were found, but measured as receptor binding total level. Unfortunately they named these endorphins, too, while we find that these are probably exorphins.

Opioids affect uptake and release of monoamines, and long...  Read more

Serotonin Transmission in Mental Disorders
As always, Greengard makes outstanding contributions. Very, very interesting.

We, as well as several other groups, have demonstrated peptide increases in schizophrenia (Hole et al., 1979; Drysdale et al., 1982; Idei et al., 1982; Cade et al., 2000) and also in several other disorders (e.g., Cade et al., 2000; Reichelt and Knivsberg, 2003). This confirms older data from Sweden (Lindstrom et al., 1986), where opioids were found, but measured as receptor binding total level. Unfortunately they named these endorphins, too, while we find that these are probably exorphins.

Opioids affect uptake and release of monoamines, and long ago we could demonstrate uptake inhibition of dopamine and serotonin (Hole et al., 1979), and later a serotonin uptake stimulating tripeptide, which in oocytes from frog stimulate the transport protein in a bell-shaped dose response (hormetic) manner (Pedersen et al., 1999; Keller, 1997). There has been some dispute about the structure of the tripeptide, and we are re-running mass spectrometry as soon as possible to see if we made any mistake. The structure we arrived at was pyroglu-trp- glyNH2 and in depression (in press) pyroglu-trp-gly.

Peptides are a bit tricky because of their considerable tendency to aggregate (Reichelt, in press), which might explain some of the problems. We use tri-fluoroacetic acid (TFA) on HPLC, therefore, and offline mass spectrometry in methanol formic acid (10mM). Formic acid 10mM is not electrometrically as strong and dissociating as TFA. (The mass spectrometry does not tolerate TFA well). In our hands, formic acid 10 mM does not deaggregate all peptide complexes.

Be that as it may, peptides regulating uptake and release of transmitters have been neglected too long. Also, the immune data on peptides in brain should by and large have been confirmed by independent methods such as HPLC and also, preferably, mass spectrometry. Immuno-like does not really ensure identity. For an overview of schizophrenia in this regard, see Reichelt et al, 1996.

We do not know what percentage of the schizophrenics show peptide increases, but a fairly large untreated cohort does. (We have great problems in getting untreated patient urine, 10 ml of the first morning urine (frozen) of carefully diagnosed cases). Our data seem able to explain the onset and suggest reasonable treatment, as shown for autism (Knivsberg et al., 1995; Knivsberg et al., 2002). It does not apply to all, of course, but a large percentage. The curse of medicine is that diagnosis is usually based on symptoms and not aetiology, almost like Morbus febris once was a diagnosis, but with a thousand different causes. We have suffered considerable opposition as would be expected, but now seem to get support from many experiments carried out properly.

References:

Cade RJ, Privette M, Fregly M, Rowland N, Sun Z, Zele V, Wagemaker H and Edelstein C (2000) Autism and schizophrenia: intestinal disorders. 3: 57-72.

Keller J. (1997) Impact of autism-related peptides and 5-HT system manipulations on cortical development and plasticity -Ist Ann report for EU proj. BMH4-CT96-0730 pp 1-10.

Knivsberg A-M, Reichelt KL, Nödland M and Höien T. (1995) Autistic syndromes and diet :a follow up study. Scand J Educat. Res 39: 225-236.

Proof that model organisms can “suffer” from psychiatric illness is at very best modest. However, the use of animal models gets around this either through symptom modeling or studying endophenotypes (see recent SRF endophenotype discussion and Gould and Gottesman, 2005). Thus, only facets, whether they be face valid “re-creations” of symptoms or models of inherent and quantifiable measures of brain functions, are utilized.

The recent paper by Svennignsson, Greengard, and colleagues takes advantage of these approaches to describe a novel function of p11, namely, the modulation of depression-like states. This includes increased tail suspension test (TST) immobility in mice where p11 has been removed (knockout; KO mice), and decreased TST immobility in mice that overexpress p11. Further, p11 KO mice spent more time along the “safer” sides of an open field, while mice overexpressing p11 tended to...  Read more

Proof that model organisms can “suffer” from psychiatric illness is at very best modest. However, the use of animal models gets around this either through symptom modeling or studying endophenotypes (see recent SRF endophenotype discussion and Gould and Gottesman, 2005). Thus, only facets, whether they be face valid “re-creations” of symptoms or models of inherent and quantifiable measures of brain functions, are utilized.

The recent paper by Svennignsson, Greengard, and colleagues takes advantage of these approaches to describe a novel function of p11, namely, the modulation of depression-like states. This includes increased tail suspension test (TST) immobility in mice where p11 has been removed (knockout; KO mice), and decreased TST immobility in mice that overexpress p11. Further, p11 KO mice spent more time along the “safer” sides of an open field, while mice overexpressing p11 tended to move away from the sides. These data are consistent with evidence that p11 is involved in modulating cellular pathways involved in depression-like and anxiety-like behavior. There are a number of additional behavioral tasks related to depression-like (e.g., forced swim test, learned helplessness) and anxiety-like (e.g., the elevated plus maze and black/white box) behavior, which could be studied in these mice. Additionally, the researchers used modern molecular and cellular biology, in addition to electrophysiological techniques, to strongly make the case that the behavioral changes likely involve interactions with the 5-HT1B receptor.

The authors “link” their basic science and rodent behavior data to humans by showing that both mRNA and protein levels of p11 are decreased in the postmortem brain of depressed patients compared to control subjects. Their finding that both ECT and imipramine increase p11 levels in the mouse brain suggests that similar effects could occur in humans. However, caution is warranted: The present field of psychiatric genetics was initiated with the understanding that human diseases are complex in nature—needing multiple genes working in disharmony with nongenetic contributors for the human syndrome. Thus, while a single gene disruption (e.g., p11) in the mouse may result in “human-related” psychiatric phenotypes, in humans, any involvement of p11 in the pathophysiology or treatment of mood disorders undoubtedly requires complex interactions with other susceptibility genes.

References:
Gould TD, Gottesman II (in press): Psychiatric endophenotypes and the development of valid animal models. Genes, Brain, and Behavior. (full text courtesy of Genes, Brain, and Behavior)

It's most interesting that Paul Greengard and colleagues report lower levels of p11 in brain samples from depressed patients. Renegunta et al. report that knockdown of p11 with siRNA enhanced trafficking of TASK-1 to the surface membrane. Hopwood et al. find that present data suggest that the excitatory effects of 5-HT on DVN are mediated in part by inhibition of a TASK-like, pH-sensitive K+ conductance, and the Perrier group reports that 5-HT1A receptors inhibit TASK-1-like K+ current in the adult turtle. Might we suspect that a specific inhibitor of TASK-1 conductance would be beneficial in depression, and might this in part explain the benefit reported by SSRIs and agents with 5-HT1A receptor agonist activity in the treatment of depression?

References:
Renigunta V, Yuan H, Zuzarte M, Rinne S, Koch A, Wischmeyer E, Schlichthorl G, Gao Y, Karschin A, Jacob R, Schwappach B, Daut J, Preisig-Muller R. The Retention Factor p11 Confers an Endoplasmic Reticulum-Localization Signal to the Potassium Channel TASK-1. Traffic. 2006 Feb;7(2):168-81. Abstract

Hopwood SE, Trapp S. TASK-like K+ channels mediate effects of 5-HT and extracellular pH in rat dorsal vagal neurones in vitro. J Physiol. 2005 Oct 1;568(Pt 1):145-54. Epub 2005 Jul 14. Abstract

Perrier JF, Alaburda A, Hounsgaard J. 5-HT1A receptors increase excitability of spinal motoneurons by inhibiting a TASK-1-like K+ current in the adult turtle. J Physiol. 2003 Apr 15;548(Pt 2):485-92. Epub 2003 Mar 7. Abstract

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Kunii et al. used two different TaqMan Assays (Applied Biosystems) to compare expression levels of full-length (FL) and truncated DARPP-32 (t-DARPP-32) in various regions of the brain, and detected increased expression of t-DARPP-32 in DLPFC in both schizophrenia and bipolar disorder samples compared to controls. Overexpression of genes can cause developmental abnormalities in the brain. For example, increased LIS1 expression can lead to significant brain abnormalities in humans and mice (Bi et al., 2009).

We previously showed increased expression of DARPP-32 in human DLPFC tissue from both schizophrenia (n = 33) and bipolar disorder (n = 32) samples using the same TaqMan assay (Hs00259967_ml) as above (this detects both FL-DARPP-32 and t-DARPP-32), after excluding brain weight, age of onset, postmortem interval, time in hospital, duration of illness and antipsychotics, gender, race, smoking, alcohol, drugs, suicide status, family history, insight and psychotic features as potential confounding factors (  Read more

Kunii et al. used two different TaqMan Assays (Applied Biosystems) to compare expression levels of full-length (FL) and truncated DARPP-32 (t-DARPP-32) in various regions of the brain, and detected increased expression of t-DARPP-32 in DLPFC in both schizophrenia and bipolar disorder samples compared to controls. Overexpression of genes can cause developmental abnormalities in the brain. For example, increased LIS1 expression can lead to significant brain abnormalities in humans and mice (Bi et al., 2009).

We previously showed increased expression of DARPP-32 in human DLPFC tissue from both schizophrenia (n = 33) and bipolar disorder (n = 32) samples using the same TaqMan assay (Hs00259967_ml) as above (this detects both FL-DARPP-32 and t-DARPP-32), after excluding brain weight, age of onset, postmortem interval, time in hospital, duration of illness and antipsychotics, gender, race, smoking, alcohol, drugs, suicide status, family history, insight and psychotic features as potential confounding factors (Zhan et al., 2011). After applying Bonferroni corrections to account for multiple comparisons, our findings remained significant, and after correcting for brain pH our p-values became much more significant (p <0.001 for both schizophrenia and bipolar disorder samples vs. controls [n = 34]).

Hierarchical clustering analysis of our data revealed a distinct pattern for DARPP-32 expression in comparison to other dopamine signaling genes and dopamine receptors D1-D5, although the expression of these genes appeared to be co-regulated with the exception of dopamine receptors and D2, in particular (Zhan et al., 2011). DARPP-32 expression in relation to D2 expression is strikingly different in controls but remarkably similar in schizophrenia and bipolar samples, suggesting aberrant D2-regulated expression of DARPP-32 may be an important trigger in pathogenesis.

We found increased DARPP-32 expression in DLPFC of schizophrenia and bipolar samples by using an assay that detects both FL-DARPP-32 and t-DARPP-32. We are, therefore, unable to say whether this is attributable to increased expression of FL-DARPP-32, t-DARPP-32, or both. Kunii et al. failed to find any differences in expression levels using this assay, but since they found increased expression of t-DARPP-32, this would indicate that FL-DARPP-32 expression levels have gone down in schizophrenia and bipolar samples. However, there is inevitably considerable variability between postmortem brain samples as shown in the data presented by Kunii et al. and in other studies, so this could also account for the results. Finally, it would be useful to compare the relative expression of both isoforms of the gene in the brain during various stages of development in the same patients. This might shed useful light on their respective functions.

References:

Zhan L, Kerr JR, Lafuente M-J, Maclean A, Chibalina MV, Liu B, Burke B, Bevan S, Nasir J. (2011) Altered expression and coregulation of dopamine signalling genes in schizophrenia and bipolar disorder. Neuropathology and Applied Neurobiology 37, 206-219. Abstract

Bi W, Sapir T, Shchelochkov OA, Zhang F, Withers MA, Hunter JV, Levy T, Shinder V, Peiffer DA, Gunderson KL, Nezarati MM, Shotts VA, Amato SS, Savage SK, Harris DJ, Day-Salvatore DL, Horner M, Lu XY, Sahoo T, Yanagawa Y, Beaudet AL, Cheung SW, Martinez S, Lupski JR, Reiner O. (2009) Increased LIS1 expression affects human and mouse brain development. Nat Genet. 41:168-177. Abstract