Caprylic acid attenuates amyloid-ß proteotoxicity by supplying energy via ß-oxidation in an Alzheimer's disease model of the nematode Caenorhabditis elegans.

Computer-based analysis of motility was used as a measure of amyloid-ß (Aß) proteotoxicity in the transgenic strain GMC101, expressing human Aß1-42 in body wall muscle cells. Aß-aggregation was quantified to relate the effects of caprylic acid (CA) to the amount of the proteotoxic protein. Gene knockdowns were induced through RNA-interference (RNAi). Moreover, the estimation of adenosine triphosphate (ATP) levels, the mitochondrial membrane potential (MMP) and oxygen consumption served the evaluation of mitochondrial function. CA improved the motility of GMC101 nematodes and reduced Aß aggregation. Whereas RNAi for orthologues encoding key enzymes for α-lipoic acid and ketone bodies synthesis did not affect motility stimulation by CA, knockdown of orthologues involved in ß-oxidation of fatty acids diminished its effects. The efficient energy gain by application of CA was finally proven by the increase of ATP levels in association with increased oxygen consumption and MMP. In conclusion, CA attenuates Aß proteotoxicity by supplying energy via FAO. Since especially glucose oxidation is disturbed in Alzheimer´s disease, CA could potentially serve as an alternative energy fuel.

4-Phenylbutyric acid attenuates amyloid-ß proteotoxicity through activation of HSF-1 in an Alzheimer's disease model of the nematode Caenorhabditiselegans.

Alzheimer's disease (AD) is a neurodegenerative disorder and the most common form of dementia. The pathogenesis is a complex process, in which the proteotoxicity of amyloid-ß (Aß) was identified as a major factor. 4-Phenylbutyric acid (4-PBA) is an aromatic short-chain fatty acid that may attenuate Aß proteotoxicity through its already shown properties as a chemical chaperone or by inhibition of histone deacetylases (HDACs). In the present study, we investigated the molecular effects of 4-PBA on Aß proteotoxicity using the nematode Caenorhabditis elegans as a model. Computer-based analysis of motility was used as a measure of Aß proteotoxicity in the transgenic strain GMC101, expressing human Aß1-42 in body wall muscle cells. Aß aggregation was quantified using the fluorescent probe NIAD-4 to correlate the effects of 4-PBA on motility with the amount of the proteotoxic protein. Furthermore, these approaches were supplemented by gene regulation via RNA interference (RNAi) to identify molecular targets of 4-PBA. 4-PBA improved the motility of GMC101 nematodes and reduced Aß aggregation significantly. Knockdown of hsf-1, encoding an ortholog essential for the cytosolic heat shock response, prevented the increase in motility and decrease in Aß aggregation by 4-PBA incubation. RNAi for hda-1, encoding an ortholog of histone deacetylase 2, also increased motility. Double RNAi for hsf-1 and hda-1 revealed a dominant effect of hsf-1 RNAi. Moreover, 4-PBA failed to further increase motility under hda-1 RNAi. Accordingly, the results suggest that 4-PBA attenuates Aß proteotoxicity in an AD-model of C. elegans through activation of HSF-1 via inhibition of HDA-1.

The Role of Norepinephrine and α-Adrenergic Receptors in Acute Stress-Induced Changes in Granulocytes and Monocytes.

OBJECTIVE: Acute stress induces redistribution of circulating leucocytes in humans. Although effects on lymphocytes as adaptive immune cells are well understood, the mechanisms underlying stress effects on granulocytes and monocytes as innate immune blood cells are still elusive. We investigated whether the stress hormone norepinephrine (NE) and α-adrenergic receptors (α-ADRs) may play a mediating role. METHODS: In a stress study, we cross-sectionally tested 44 healthy men for associations between stress-induced NE increases and simultaneous granulocyte and monocyte cell count increases, as measured immediately before and several times after the Trier Social Stress Test. In a subsequent infusion study, 21 healthy men participated in three different experimental trials with sequential infusions of 1- and 15-minute duration with varying substances (saline as placebo, the nonspecific α-ADR blocker phentolamine [2.5 mg/min], and NE [5 µg/min]): trial 1 = saline+saline, trial 2 = saline+NE, trial 3 = phentolamine+NE. Granulocyte and monocyte cell numbers were assessed before, immediately after, 10 minutes, and 30 minutes after infusion procedures. RESULTS: In the stress study, higher NE related to higher neutrophil stress changes (ß = .31, p = .045, R change = .09), but not epinephrine stress changes. In the infusion study, saline+NE induced significant increases in neutrophil (F(3/60) = 43.50, p < .001, η = .69) and monocyte (F(3/60) = 18.56, p < .001, η = .48) numbers compared with saline+saline. With phentolamine+NE, neutrophil (F(3/60) = 14.41, p < .001, η = .42) and monocyte counts (F(2.23/44.6) = 4.32, p = .016, η = .18) remained increased compared with saline+saline but were lower compared with saline+NE (neutrophils: F(3/60) = 19.55, p < .001, η = .494, monocytes: F(3/60) = 2.54, p = .065, η = .11) indicating partial mediation by α-ADRs. Trials did not differ in eosinophil and basophil count reactivity. CONCLUSIONS: Our findings suggest that NE-induced immediate increases in neutrophil and monocyte numbers resemble psychosocial stress effects and can be reduced by blockade of α-ADRs.

Serotonin is required for exercise-induced adult hippocampal neurogenesis.

Voluntary wheel running has long been known to induce precursor cell proliferation in adult hippocampal neurogenesis in rodents. However, mechanisms that couple activity with the promitotic effect are not yet fully understood. Using tryptophan hydroxylase (TPH) 2 deficient (Tph2-deficient) mice that lack brain serotonin, we explored the relationship between serotonin signaling and exercise-induced neurogenesis. Surprisingly, Tph2-deficient mice exhibit normal baseline hippocampal neurogenesis but impaired activity-induced proliferation. Our data demonstrate that the proproliferative effect of running requires the release of central serotonin in young-adult and aged mice. Lack of brain serotonin further results in alterations at the stage of Sox2-positive precursor cells, suggesting physiological adaptations to changes in serotonin supply to maintain homeostasis in the neurogenic niche. We conclude that serotonin plays a direct and acute regulatory role in activity-dependent hippocampal neurogenesis. The understanding of exercise-induced neurogenesis might offer preventive but also therapeutic opportunities in depression and age-related cognitive decline.

RNA-interference in the nematode Caenorhabditis elegans is effective using paraformaldehyde-inactivated E. coli HT115 bacteria as a food source.

The nematode Caenorhabditis elegans is a widely used research model for the investigation of metabolism, aging and age-associated diseases. However, when investigating the impact of natural compounds or drugs on those topics, a major confounder is the metabolism of these test substances by live E. coli bacteria, the standard food source of C. elegans. Using paraformaldehyde instead of heat to inactivate E. coli, which allows for high-throughput technologies and better food availability, it is shown here that RNA-interference works equally well, thus demonstrating the absence of considerable interfering modifications of paraformaldehyde with nucleic acids.

Reduced isolation-induced pup ultrasonic communication in mouse pups lacking brain serotonin.

BACKGROUND: Serotonin (5-hydroxytryptamine, 5-HT) is a key modulatory neurotransmitter in the mammalian central nervous system (CNS) that plays an important role as a developmental signal. Several lines of evidence associate altered 5-HT signaling with psychopathology in humans, particularly neurodevelopmental disorders such as autism spectrum disorders (ASD). ASD are characterized by persistent social and communication deficits along with stereotyped and repetitive patterns of behavior, with all symptoms emerging early during development. METHODS: Here, we employed a mouse model devoid of brain 5-HT due to the lack of the gene encoding tryptophan hydroxylase 2 (Tph2), the initial and rate-limiting enzyme of 5-HT synthesis in the CNS. Tph2 null mutant (Tph2 (-/-) ) mice show normal prenatal development; however, they display for yet unknown reasons severe growth retardation during the first postnatal weeks. We investigated, therefore, whether Tph2 (-/-) mice display deficits in isolation-induced ultrasonic vocalizations (USV) as pups during early life. Isolation-induced USV are the most commonly studied behavioral measure to assess developmental delays and communication deficits in rodent models for ASD, particularly as they serve an important communicative function in coordinating mother-pup interactions. RESULTS: Tph2 (-/-) mouse pups displayed a clear deficit in the emission of isolation-induced USV, as compared to heterozygous and wildtype littermates, exactly during growth retardation onset, including reduced call numbers and deficits in call clustering and temporal organization. CONCLUSIONS: The ultrasonic communication impairment displayed by Tph2 (-/-) mouse pups is likely to result in a deficient mother-infant interaction, presumably contributing to their growth retardation phenotype, and represents a prominent feature relevant to ASD.

Life without brain serotonin: reevaluation of serotonin function with mice deficient in brain serotonin synthesis.

Tryptophan hydroxylase (TPH) is a rate limiting enzyme in the synthesis of serotonin (5-HT), a monoamine which works as an autacoid in the periphery and as a neurotransmitter in the central nervous system. In 2003 we have discovered the existence of a second Tph gene, which is expressed exclusively in the brain, and, therefore, is responsible for the 5-HT synthesis in the central nervous system. In the following years several research groups have independently generated Tph2-deficient mice. In this review we will summarize the data gained from the existing mouse models with constitutive or conditional deletion of the Tph2 gene, focusing on biochemical, developmental, and behavioral consequences of Tph2-deficiency.

Adaptive changes in serotonin metabolism preserve normal behavior in mice with reduced TPH2 activity.

Polymorphisms in the TPH2 gene coding for the serotonin synthesizing enzyme in the brain are considered as risk factors associated with depression and anxiety in humans. However, whether a certain variation in the TPH2 gene leads to decreased brain serotonin production and development of psychological abnormalities remains unresolved. We generated a new mouse model, carrying one Tph2-null allele and one Tph21473G-allele, coding for a hypoactive form of the enzyme. We tested these mice along with C57BL/6 mice (Tph2C/C), congenic C57BL/6 mice homozygous for the Tph21473G-allele (Tph2G/G), and heterozygous Tph2-deficient mice (Tph2C/-) for anxiety- and depression-like behavior, and evaluated brain serotonin metabolism and 5-HT1AR signaling by high-performance liquid chromatography and quantitative autoradiography, respectively. Progressive reduction in TPH2 activity had no effect on emotional behavior, and only slightly affected brain serotonin levels. However, serotonin degradation rate was drastically decreased in mice with reduced TPH2 activity, thereby compensating for the lowered rate of serotonin production in these mice. In addition, the hypothermic response to the 5-HT1AR agonist, 8-OH-DPAT, was attenuated in mice with reduced serotonin production. In contrast, 5-HT1A autoreceptor density and G-protein coupling were not changed in mice with gradual decrease in central serotonin. Taken together, these data suggest that in conditions of reduced serotonin production lowered serotonin degradation rate contributes to the maintenance of brain serotonin at levels sufficient for adequate behavior responses. These findings reveal that decreased TPH2 activity cannot be considered a reliable predisposition factor for impaired emotional behavior.

Evidence for a supportive role of classical transient receptor potential 6 (TRPC6) in the exploration behavior of mice.

Non-selective classical transient receptor potential (TRPC) cation channels share important roles in processes of neuronal development and function. To test the influence of TRPC6 activity on behavior, we developed a TRPC6-deficient (TRPC6(-/-)) mouse model in a BALB/c genetic background. Both, TRPC6(-/-) and wild-type (WT) mice were analyzed first for their general health and reflex status (modified SHIRPA protocol) and then in three different behavioral tests (marble-burying test, square open field and elevated star maze). No abnormalities were detected in the SHIRPA protocol. Most interestingly, TRPC6(-/-) mice showed no significant differences in anxiety in a marble-burying test, but demonstrated reduced exploration in the square open field and the elevated star maze. Therefore, TRPC6 channel activity may play a yet unknown role for exploration behavior.