Metabolic characterization of primary human colorectal cancers using high resolution magic angle spinning 1H magnetic resonance spectroscopy

Colorectal cancer is one of the most frequent and most lethal forms of cancer in the western world. The aim of this study is to characterize by ¹H high resolution magic angle spinning NMR spectroscopy (HRMAS) the metabolic fingerprint of both tumoral and healthy tissue samples obtained from a cohort of patients affected by primary colorectal adenocarcinoma. By analyzing HRMAS data using multivariate statistical analysis (PLS-DA), the two types of tissues could be discriminated with a high level of confidence. The identification of the metabolites at the origin of this discrimination revealed that adenocarcinomas are richer in taurine, glutamate, aspartate, and lactate whereas healthy tissues contain a higher amount of myo-inositol and β-glucose. The statistical model resulting from the PLS-DA analysis was subsequently used to perform a blind test on tumoral and healthy colon biopsies. The results of the classification showed that the HRMAS analysis has very high sensitivity and specificity.     

Taurine deficiency damages retinal neurones: cone photoreceptors and retinal ganglion cells

In 1970s, taurine deficiency was reported to induce photoreceptor degeneration in cats and rats. Recently, we found that taurine deficiency contributes to the retinal toxicity of vigabatrin, an antiepileptic drug. However, in this toxicity, retinal ganglion cells were degenerating in parallel to cone photoreceptors. The aim of this study was to re-assess a classic mouse model of taurine deficiency following a treatment with guanidoethane sulfonate (GES), a taurine transporter inhibitor to determine whether retinal ganglion cells are also affected. GES treatment induced a significant reduction in the taurine plasma levels and a lower weight increase. At the functional level, photopic electroretinograms were reduced indicating a dysfunction in the cone pathway. A change in the autofluorescence appearance of the eye fundus was explained on histological sections by an increased autofluorescence of the retinal pigment epithelium. Although the general morphology of the retina was not affected, cell damages were indicated by the general increase in glial fibrillary acidic protein expression. When cell quantification was achieved on retinal sections, the number of outer/inner segments of cone photoreceptors was reduced (20?%) as the number of retinal ganglion cells (19?%). An abnormal synaptic plasticity of rod bipolar cell dendrites was also observed in GES-treated mice. These results indicate that taurine deficiency can not only lead to photoreceptor degeneration but also to retinal ganglion cell loss. Cone photoreceptors and retinal ganglion cells appear as the most sensitive cells to taurine deficiency. These results may explain the recent therapeutic interest of taurine in retinal degenerative pathologies.     

Intérêt de la tomoscintigraphie cardiaque à la 123I-mIBG couplée à la perfusion myocardique dans le diagnostic de l’atrophie multisystématisée

ObjectiveThe aim of this prospective study is to assess the pertinence of using ¹²³I-mIBG myocardial tomoscintigraphy coupled with perfusion scintigraphy as a diagnostic tool, to discriminate between multiple system atrophy (MSA) and idiopathic Parkinson's disease (PD) at first guided by clinical data and L-DOPA tests.Material and methodsForty patients, aged from 43 to 78 years (median 62 years) with Parkinson's syndrome were studied. Nineteen had a diagnosis of PD (criteria of brain bank) and 21 AMS (Gibbs criteria). All were given test to acute L-DOPA. Chest-centered planar imaging (128 × 128 matrix, 5 minutes of duration) is performed at 1 hour and 4 hours after injection of 220 MBq of ¹²³I-mIBG, in addition a non-synchronised tomoscintigraphy (64 × 64 matrix, 32 images of 50 seconds , zoom 1.45) was performed after the 4th hour and 15 minutes after injection of 200 to 400 MBq of ^99mTc-tetrofosmin. Besides neurological data, the parameters retained for comparison purposes with ¹²³I-mIBG cardiac tomoscintigraphy were patients’ age, duration of disease and L-DOPA test results. Two regions of interest (ROI) identical in size and in shape are used for ¹²³I-mIBG uptake quantifications (H/M and washout [Wo]). The first one was placed in projection of mediastinum (M) and the other one in projection of heart (H).ResultsWe found an overall decreased uptake of the myocardial ¹²³I-mIBG without perfusion abnormality in 15 of 19 patients with PD and 11 among them were L-DOPA sensitive (L-DOPA test greater than 30%). Normal tracer uptake with ¹²³I-mIBG associated with an almost quite normal perfusion was seen in 15 of 21 patients with MSA and they were little or not L-DOPA sensitive (L-DOPA test less than 30%). Therefore, 10 discordant cases (25%) between cardiac scintigraphy and clinical evolution of disease with also discordant L-DOPA tests were observed. In the PD group, quantification of data enhanced the diagnostic decision with low heart to mediastinum ratio (H/M) (1.32 ± 0.15 at the early stage and 1.25 ± 0.13 at the later stage). In the MSA group, the uptake of ¹²³I-mIBG (1.66 ± 0.43 at the early stage and 1.72 ± 0.42 at the later stage) was comparable to literature data, however, with significant inter-individual variations. The association of data of scintigraphy with L-DOPA test allows to improve sensitivity in 84% and specificity in 90.5%.ConclusionOur prospective study of 40 cases shows the relevance of cardiac sympathetic postganglionic imaging with ¹²³I-mIBG coupled with myocardial perfusion scintigraphy to discriminate between MSA and PD with a higher sensitivity (71.4%) compared to the test with L-DOPA but a lower specificity (78.9%) than the L-DOPA. The difficulty of diagnosis is firstly linked to damage occurring to both the pre- and postganglionic sympathetic systems in patients with MSA and secondly to the integrity of the sympathetic nerve endings in patients with PD. However, the association of data of scintigraphy with L-DOPA test show a significant improvement of sensibility (84%).     

A New Specific Succinate-Glutamate Metabolomic Hallmark in Sdhx-Related Paragangliomas

Paragangliomas (PGLs) are frequently associated with germline mutations in genes involved in energy metabolism. The purpose of the present study was to assess whether the tumor metabolomic profile of patients with hereditary and apparently sporadic PGLs enables the distinction of different subtypes of tumors. Twenty-eight unrelated patients with a histological diagnosis of PGLs were included in the present study. Twelve had germline mutations in SDHx genes (5 SDHB, 7 SDHD), 6 VHL, and 10 were apparently sporadic. Intact tumor samples from these patients (one per patient) were evaluated with ¹H high-resolution magic angle spinning (HRMAS) NMR spectroscopy. SDHx-related tumors were characterized by an increase in succinate levels in comparison to other tumor subtypes (p = 0.0001 vs VHL and p = 0.000003 vs apparently sporadic). Furthermore, we found significantly lower values of glutamate in SDHx-related tumors compared to other subtypes (p = 0.0007 vs VHL and p = 0.003 vs apparently sporadic). Moreover, SDHx-tumors also exhibited lower values of ATP/ADP/AMP (p = 0.01) compared to VHL. VHL tumors were found to have the highest values of glutathione (GSH) compared to other tumors. Based on 4 metabolites (succinate, glutamate, GSH, and ATP/ADP/AMP), tumors were accurately distinguished from the other ones on both 3- and 2-class PLS-DA models. The present study shows that HRMAS NMR spectroscopy is a very promising method for investigating the metabolomic profile of various PGLs. The present data suggest the existence of a specific succinate-glutamate hallmark of SDHx PGLs. The relevance of such a metabolomic hallmark is expected to be very useful in designing novel treatment options as well as improving the diagnosis and follow-up of these tumors, including metastatic ones.     

C-Fiber Recovery Cycle Supernormality Depends on Ion Concentration and Ion Channel Permeability

Following each action potential, C-fiber nociceptors undergo cyclical changes in excitability, including a period of superexcitability, before recovering their basal excitability state. The increase in superexcitability during this recovery cycle depends upon their immediate firing history of the axon, but also determines the instantaneous firing frequency that encodes pain intensity. To explore the mechanistic underpinnings of the recovery cycle phenomenon a biophysical model of a C-fiber has been developed. The model represents the spatial extent of the axon including its passive properties as well as ion channels and the Na/K-ATPase ion pump. Ionic concentrations were represented inside and outside the membrane. The model was able to replicate the typical transitions in excitability from subnormal to supernormal observed empirically following a conducted action potential. In the model, supernormality depended on the degree of conduction slowing which in turn depends upon the frequency of stimulation, in accordance with experimental findings. In particular, we show that activity-dependent conduction slowing is produced by the accumulation of intraaxonal sodium. We further show that the supernormal phase results from a reduced potassium current K_dr as a result of accumulation of periaxonal potassium in concert with a reduced influx of sodium through Na_v1.7 relative to Na_v1.8 current. This theoretical prediction was supported by data from an in vitro preparation of small rat dorsal root ganglion somata showing a reduction in the magnitude of tetrodotoxin-sensitive relative to tetrodotoxin -resistant whole cell current. Furthermore, our studies provide support for the role of depolarization in supernormality, as previously suggested, but we suggest that the basic mechanism depends on changes in ionic concentrations inside and outside the axon. The understanding of the mechanisms underlying repetitive discharges in recovery cycles may provide insight into mechanisms of spontaneous activity, which recently has been shown to correlate to a perceived level of pain.     

Sea-anemone toxin ATX-II elicits A-fiber-dependent pain and enhances resurgent and persistent sodium currents in large sensory neurons

Background

Despite decades of intense research efforts, actions of acute opioids are not fully understood. Increasing evidence suggests that in addition to well-documented antinociceptive effects opioids also produce paradoxical hyperalgesic and excitatory effects on neurons. However, most studies focus on the pronociceptive actions of chronic opioid exposure. Matrix metalloproteinase 9 (MMP-9) plays an important role in neuroinflammation and neuropathic pain development. We examined MMP-9 expression and localization in dorsal root ganglia (DRGs) after acute morphine treatment and, furthermore, the role of MMP-9 in modulating acute morphine-induced analgesia and hyperalgesia in mice.

Results

Subcutaneous morphine induced a marked up-regulation of MMP-9 protein in DRGs but not spinal cords. Morphine also increased MMP-9 activity and mRNA expression in DRGs. MMP-9 up-regulation peaked at 2 h but returned to the baseline after 24 h. In DRG tissue sections, MMP-9 is expressed in small and medium-sized neurons that co-express mu opioid receptors (MOR). In DRG cultures, MOR agonists morphine, DAMGO, and remifentanil each increased MMP-9 expression in neurons, whereas the opioid receptor antagonist naloxone and the MOR-selective antagonist D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH₂ (CTAP) suppressed morphine-induced MMP-9 expression. Notably, subcutaneous morphine-induced analgesia was enhanced and prolonged in Mmp9 knockout mice and also potentiated in wild-type mice receiving intrathecal injection of MMP-9 inhibitors. Consistently, intrathecal injection of specific siRNA targeting MMP-9 reduced MMP-9 expression in DRGs and enhanced and prolonged morphine analgesia. Subcutaneous morphine also produced heat hyperalgesia at 24 h, but this opioid-induced hyperalgesia was not enhanced after MMP-9 deletion or inhibition.

Conclusions

Transient MMP-9 up-regulation in DRG neurons can mask opioid analgesia, without modulating opioid-induced hyperalgesia. Distinct molecular mechanisms (MMP-9 dependent and independent) control acute opioid-induced pronociceptive actions (anti-analgesia in the first several hours and hyperalgesia after 24 h). Targeting MMP-9 may improve acute opioid analgesia.