Cadaverine in the brain of axenic mice

Alzheimer's disease as a chronic maladaptive polyamine stress response

Polyamines are nitrogen-rich polycationic ubiquitous bioactive molecules with diverse evolutionary-conserved functions. Their activity interferes with numerous genes' expression resulting in cell proliferation and signaling modulation. The intracellular levels of polyamines are precisely controlled by an evolutionary-conserved machinery. Their transient synthesis is induced by heat stress, radiation, and other traumatic stimuli in a process termed the polyamine stress response (PSR). Notably, polyamine levels decline gradually with age; and external supplementation improves lifespan in model organisms. This corresponds to cytoprotective and reactive oxygen species scavenging properties of polyamines. Paradoxically, age-associated neurodegenerative disorders are characterized by upsurge in polyamines levels, indicating polyamine pleiotropic, adaptive, and pathogenic roles. Specifically, arginase overactivation and arginine brain deprivation have been shown to play an important role in Alzheimer's disease (AD) pathogenesis. Here, we assert that a universal short-term PSR associated with acute stimuli is beneficial for survival. However, it becomes detrimental and maladaptive following chronic noxious stimuli, especially in an aging organism. Furthermore, we regard cellular senescence as an adaptive response to stress and suggest that PSR plays a central role in age-related neurodegenerative diseases' pathogenesis. Our perspective on AD proposes an inclusive reassessment of the causal relationships between the classical hallmarks and clinical manifestation. Consequently, we offer a novel treatment strategy predicated upon this view and suggest fine-tuning of arginase activity with natural inhibitors to preclude or halt the development of AD-related dementia.

Cadaverine and Spermine Elicit Ca2+ Uptake in Human CP Cells via a Trace Amine-Associated Receptor 1 Dependent Pathway

The choroid plexus (CP) constitutes a barrier between the blood and the cerebrospinal fluid (CSF) which regulates the exchange of substances between these two fluids through mechanisms that are not completely understood. Polyamines as spermine, spermidine and putrescine are produced by all cells and are present in the CSF. Interestingly, their levels are altered in some neuronal disorders as Alzheimer's and Parkinson's diseases, thus increasing the interest in their signalling in the central nervous system (CNS). Cadaverine, on the other hand, is synthetized by the intestinal microbiome, suggesting that the presence of this bacterial metabolite in the CSF requires that it is up taken to the CNS across brain barriers. We knew that polyamines are detected by the olfactory signalling cascade operating at the CP, but the receptor involved had not been identified. The zebrafish TAAR13c was the only receptor known to bind a polyamine-cadaverine. Thus, we searched for a human receptor with homology to TAAR13c and found that some human TAARs including TAAR1 showed great homology. Then, we confirmed the expression of TAAR1 mRNA and protein in a human cell line of the CP, and in human CP samples. Calcium imaging assays after TAAR1 knockdown in these cells with a specific siRNA against TAAR1 showed a consistent reduction in the responses of these cells to cadaverine and spermidine, but not to spermine, suggesting that TAAR1 is activated by cadaverine and spermidine, but not spermine.

The pathway of subarachnoid CSF moving into the spinal parenchyma and the role of astrocytic aquaporin-4 in this process

AIMS

It has been proved that cerebrospinal fluid (CSF) in the subarachnoid space could reenter the brain parenchyma via the perivascular space. The present study was designed to explore the pathway of subarachnoid CSF flux into the spinal cord and the potential role of aquaporin-4 (AQP4) in this process.

MAIN METHODS

Fluorescently tagged cadaverine, for the first time, was used to study CSF movement in mice. Following intracisternal infusion of CSF tracers, the cervical spinal cord was sliced and prepared for fluorescence imaging. Some sections were subject with immunostaining in order to observe tracer distribution and AQP4 expression.

KEY FINDINGS

Fluorescently tagged cadaverine rapidly entered the spinal cord. Tracer influx into the spinal parenchyma was time dependent. At 10min post-infusion, cadaverine was largely distributed in the superficial tissue adjacent to the pial surface. At 70min post-infusion, cadaverine was distributed in the whole cord and especially concentrated in the gray matter. Furthermore, fluorescent tracer could enter the spinal parenchyma either along the perivascular space or across the pial surface. AQP4 was observed highly expressed in the astrocytic endfeet surrounding blood vessels and the pial surface. Blocking AQP4 by its specific inhibitor TGN-020 strikingly reduced the inflow of CSF tracers into the spinal cord.

SIGNIFICANCE

Subarachnoid CSF could flow into the spinal cord along the perivascular space or across the pial surface, in which AQP4 is involved. Our observation provides a basis for the study on CSF movement in the spinal cord when some neurological diseases occur.

Metabolomics and neuroanatomical evaluation of post-mortem changes in the hippocampus

Understanding the human brain is the ultimate goal in neuroscience, but this is extremely challenging in part due to the fact that brain tissue obtained from autopsy is practically the only source of normal brain tissue and also since changes at different levels of biological organization (genetic, molecular, biochemical, anatomical) occur after death due to multiple mechanisms. Here we used metabolomic and anatomical techniques to study the possible relationship between post-mortem time (PT)-induced changes that may occur at both the metabolomics and anatomical levels in the same brains. Our experiments have mainly focused on the hippocampus of the mouse. We found significant metabolomic changes at 2 h PT, whereas the integrity of neurons and glia, at the anatomical/ neurochemical level, was not significantly altered during the first 5 h PT for the majority of histological markers.

The conversion of lysine into piperidine, cadaverine, and pipecolic acid in the brain and other organs of the mouse

The biosynthesis of piperidine, a possible neuromodulator, and its presumed precursors cadaverine and pipecolic acid, has been investigated in the mouse under in vitro conditions. Conversion of lysine into piperidine was observed only in the intestines and is probably caused by the intestinal flora. Formation of cadaverine and pipecolic acid from lysine was observed in the brain, liver, kidney, and large intestine. In addition, pipecolic acid was formed in the heart. The possible contributions of the diet and of the intestinal bacteria to the endogenous pool(s) of piperidine are discussed.

Metabolism of cadaverine and pipecolic acid in brain and other organs of the mouse

Cadaverine and pipecolic acid metabolism was investigated in vitro in several organs of the mouse by measuring 14CO2 formation from labeled precursors. The liver showed the highest formation of 14CO2 from [1,5-14C]-cadaverine, whereas brain demonstrated a much lower formation. Anaerobiosis or inhibition of monoamineoxidase (MAO) activity significantly reduced 14CO2 formation in every organ, but inhibition of diamine oxidase (DAO) activity had no effect in brain and kidney. Piperidine was formed from cadaverine in vitro only in the large intestine and its content. This formation is probably of bacterial origin. Under a variety of experimental conditions we were unable to demonstrate any formation of piperidine in brain from cadaverine. Biosynthesis in vitro of [3H]-piperidine from D,L-[3H]-pipecolic acid was very low in brain and kidney. With the exception of brain and kidney, no other organs showed any formation of [3H]-piperidine. Neither MAO nor DAO inhibition influenced [3H]-piperidine formation in the large intestine with its content. Following 1 hr incubation at 37 degrees C under aerobic conditions, the levels of [14C]-pipecolic acid and [3H]-piperidine recovered from mouse brain homogenate did not indicate any significant degradation of these two substances. Our results suggest that under in vitro conditions, cadaverine is not a precursor of piperidine in brain, liver, heart, and kidney and that only very low levels of piperidine can be formed from pipecolic acid in brain. Outside the brain, formation of piperidine from pipecolic acid is detectable only in kidney and in the content of the large intestine. The latter is probably of bacterial origin. Our results do not support previous findings from other authors on an endogenous origin of piperidine in brain from cadaverine and pipecolic acid, and they suggest that a) cadaverine is not a precursor of piperidine in brain, b) the conversion of pipecolic acid into piperidine in the brain does not constitute a major metabolic pathway, and c) the main source of piperidine in the CNS may be of nonneural origin.

Clinical relevance of polyamines

The polyamines, putrescine, spermidine, and spermine have been established as biochemical markers of normal and pathological growth. In malignancy, the urinary concentrations of spermidine reflect the tumor cell loss and the urinary level of putrescine is related both to the number of tumor cells in cell cycle and to the tumor cell loss factor. A greater than twofold increase in urinary spermidine within 72 hr of chemotherapy predicts a complete or a partial response with a high degree of accuracy. Urinary putrescine may be valuable, not only in assessing the early response to therapy but also in determining whether the chemotherapy promotes a later burst of cell proliferation. Erythrocyte spermidine concentrations also appear to track alterations in tumor kinetics. Alterations in intracellular and extracellular polyamines in other pathologies such as psoriasis, muscular dystrophy, and cystic fibrosis also accurately reflect the disease activity and, in those cases studied, response to therapy. Therefore, the determination of polyamine concentrations in extracellular fluids and in erythrocytes allows for (1) the early assessment of response to multimodality therapy, (2) disease or tumor staging, and (3) assessment of disease activity including long-term monitoring of polyamine concentrations to pinpoint remission and relapse in adjuvant patients. Information obtained by the monitoring of polyamines could result in prolongation of survival time of patients as well as assist in the design of the most effective therapy regimen for the pathology. Since other such specific kinetic markers are not available, polyamines should be clinically utilized to track tumor evolution and tumor response to therapy in those patients at high risk, in which such measurements could be translated into therapeutic efficacy.

Cadaverine in the rat brain: regional distribution and acylation of [14C]cadaverine in vivo and uptake in vitro

The regional distribution and acylation of intraventricularly injected [14C]cadaverine was studied in the rat brain over a 48-h period. The concentrations of labeled cadaverine and its acyl derivatives, N-monoacetylcadaverine and N-monopropionylcadaverine, were determined in the telencephalon, striatum, hypothalamus, midbrain, cerebellum, and medulla-pons by TLC of their 5-dimethylamino-1-naphthalenesulfonyl derivatives, followed by liquid scintillation spectrometry. The apparent passage of radioactivity from the ventricular space into brain tissue was slow, with the concentrations reaching a peak at 24 h after injection. The percentage of radioactivity in the acyl forms of cadaverine, however, was maximal 4 h after injection, with the propionyl form predominating. The telencephalon, striatum, and hypothalamus contained the highest concentrations of radioactivity, in all three forms, at all elapsed times. A high-affinity uptake mechanism for cadaverine was demonstrated in slices of these tissues. This process was completely inhibited by equimolar concentrations of unlabeled putrescine.

Decarboxylation of ornithine and lysine in rat tissues

The possibility that arginine and lysine might be decarboxylated by rat tissues was investigated. No evidence for decarboxylation of arginine could be found. Lysine decarbosylase (L-lysine carboxy-lyase, EC 4.1.1.18) activity producing CO2 and cadaverine was detected in extracts from rat ventral prostate, androgen-stimulated mouse kidney, regenerating rat liver and livers from rats pretreated with thioacetamide. These tissues all have high ornithine decarboxylase (L-ornithine carboxy-lyase, EC 4.1.1.17) activities. Lysine and ornithine decarboxylase activities were lost to similar extents on inhibition of protein synthesis by cycloheximide and on exposure to alpha-difluoromethylornithine. A highly purified ornithine decarboxylase preparation was able to decarboxylate lysine and the ratio of ornithine to lysine decarboxylase activities was constant throughout purification. Kinetic studies of the purified preparation showed that the V for ornithine was about 4-fold greater than for lysine, but the Km for lysine (9 mM) was 100-times greater than that for ornithine (0.09 mM). These experiments indicate that all of the detectable lysine decarboxylase activity in rat and mouse tissues was due to the action of ornithine decarboxylase and that significant cadaverine production in vivo would occur only when ornithine decarboxylase activity is high and lysine concentrations substantially exceed those of ornithine.

Formation of cadaverine in the pregnant rat

The formation as well as the content of cadaverine were determined in different tissues of pregnant and non-pregnant rats. The placenta and ovary were most potent in the ability to form cadaverine. To our knowledge this is the first report of an in vitro formation of cadaverine linked to a normal physiological process, i.e. pregnancy. The highest concentration of cadaverine was found in the placenta and ovary of the pregnant rat. Treatment with aminoguanidine generally elevated the content of cadaverine, indicating a role of diamine oxidase as a regulator of diamine content.

Monoacylcadaverines in the blood of schizophrenic patients

Concentrations of cadaverine, monoacetylcadaverine and monopropionylcadaverine in the blood of schizophrenic and nonschizophrenic subjects were measured. Two groups, one from the U.S.A. the other from Japan, were tested. Monoacetylcadaverine and monopropionylcadaverine were found elevated in the blood of some schizophrenic patients in comparison with those in controls in each group. Their increase could be caused by a reduced monoamine oxidase activity or by an increased acylation in schizophrenic patients.

Evidence of decarboxylation of lysine by mammalian ornithine decarboxylase

In enzymic preparations from mouse kidney stimulated with the anabolic steroid Durabolin (nandrolone phenpropionate) lysine and ornithine were shown to inhibit the decarboxylation of each other competitively. The Michaelis constants for the decarboxylations were approximately equal to the inhibition constants of the two amino acids. The pH optima of the decarboxylation of lysine and ornithine were found to be identical. Chromatographic studies of the enzyme preparation on a Sephadex G-150 Superfine column did not bring about a separation of the two enzyme activities. The ratio of the decarboxylating activities was practically the same during the elution. Lysine decarboxylating activity was also shown to be present in growth hormone stimulated rat liver. The results are in agreement with the assumption that the decarboxylation of lysine and ornithine is carried out by the same enzyme.

Biosynthesis of cadaverine in mice under the influence of an anabolic steroid

The content of cadaverine (1,5-diaminopentane) in the kidney and urine was investigated in mice treated with the anabolic steroid Durabolin (nondrolone phenpropionate). After administration of this steroid cadaverine was found in the kidneys, whereas this amine could not be detected in the kidney of controls. The urinary excretion of cadaverine was elevated 50 times after Durabolin administration. An enzyme catalyzing the formation of cadaverine from lysine was shown for the first time to be present in mammalian tissue, namely in the kidney of mice after Durabolin administration.