Fractionated manganese injections: effects on MRI contrast enhancement and physiological measures in C57BL/6 mice

Manganese‐enhanced MRI (MEMRI) is an increasingly used imaging method in animal research, which enables improved T₁‐weighted tissue contrast. Furthermore accumulation of manganese in activated neurons allows visualization of neuronal activity. However, at higher concentrations manganese (Mn²⁺) exhibits toxic side effects that interfere with the animals' behaviour and well‐being. Therefore, when optimizing MEMRI protocols, a compromise has to be found between minimizing side effects and intensifying image contrast. Recently, a low concentrated fractionated Mn²⁺ application scheme has been proposed as a promising alternative. In this study, we investigated effects of different fractionated Mn²⁺ dosing schemes on vegetative, behavioural and endocrine markers, and MEMRI signal contrast in C57BL/6N mice. Measurements of the animals' well‐being included telemetric monitoring of body temperature and locomotion, control of weight and observation of behavioural parameters during the time course of the injection protocols. Corticosterone levels after Mn²⁺ application served as endocrine marker of the stress response. We compared three MnCl₂ · 4H₂O application protocols: 3 times 60 mg/kg with an inter‐injection interval of 48 h, six times 30 mg/kg with an inter‐injection interval of 48 h, and 8 times 30 mg/kg with an inter‐injection interval of 24 h (referred to as 3 × 60/48, 6 × 30/48 and 8 × 30/24, respectively). Both the 6 × 30/48 and the 8 × 30/24 protocols showed attenuated effects on animals' well‐being as compared to the 3 × 60/48 scheme. Best MEMRI signal contrast was observed for the 8 × 30/24 protocol. Together, these results argue for a fractionated application scheme such as 30 mg/kg every 24 h for 8 days to provide sufficient MEMRI signal contrast while minimizing toxic side effects and distress. Copyright © 2010 John Wiley & Sons, Ltd.     

MRI in ocular drug delivery

Conventional pharmacokinetic methods for studying ocular drug delivery are invasive and cannot be conveniently applied to humans. The advancement of MRI technology has provided new opportunities in ocular drug-delivery research. MRI provides a means to non-invasively and continuously monitor ocular drug-delivery systems with a contrast agent or compound labeled with a contrast agent. It is a useful technique in pharmacokinetic studies, evaluation of drug-delivery methods, and drug-delivery device testing. Although the current status of the technology presents some major challenges to pharmaceutical research using MRI, it has a lot of potential. In the past decade, MRI has been used to examine ocular drug delivery via the subconjunctival route, intravitreal injection, intrascleral injection to the suprachoroidal space, episcleral and intravitreal implants, periocular injections, and ocular iontophoresis. In this review, the advantages and limitations of MRI in the study of ocular drug delivery are discussed. Different MR contrast agents and MRI techniques for ocular drug-delivery research are compared. Ocular drug-delivery studies using MRI are reviewed.     

Manganese threonine chelate—a new enteric contrast agent for MRI: a pilot study on rats

Enteric contrast agents are important in gastrointestinal MRI. However, no currently available agent is well established as the standard of care. In this study, in vitro relaxivities of manganese threonine chelate (Mn‐Thr), a common nutritional food supplement, were measured at 1.5 T and 3 T with further investigation of its efficacy and safety in vivo as an enteric contrast agent. According to the calculated relaxivities, T₁W and T₂W TSE sequences of Mn‐Thr solutions at different concentrations were acquired, and the optimal concentration for dark lumen imaging on both T₁W and T₂W images was determined in vitro. To validate the optimal concentration in vivo, eight Sprague‐Dawley rats were randomly divided into two groups. Each group received rectal injection of either 2.00 g/L (about 3.80 mM) Mn‐Thr or saline as an enteric contrast agent and underwent MRI. After a time interval of one week, the same procedures were repeated with the alternative contrast agent. Animals were sacrificed after the second MRI. Tissue manganese quantification and histopathological examination were obtained. Qualitative MR image quality assessments were performed and compared between Mn‐Thr and saline. Measured T₁ and T₂ relaxivities of Mn‐Thr were significantly higher than those of MnCl₂ in vitro (p < 0.05). At the concentration of 2.00 g/L (about 3.80 mM), Mn‐Thr produced a dark lumen on T₁W and T₂W images both in vitro and in vivo. Compared with saline, Mn‐Thr showed significantly more homogenous luminal signal and increased bowel wall conspicuity in image quality assessments. Tissue manganese concentrations were not significantly different between two groups. Histopathological examinations were normal in both groups. Our data suggest that Mn‐Thr possesses favorable paramagnetic properties and can create a homogenous dark lumen on T₁W and T₂W images without obvious side effects in healthy rats. As a commercially available nutritional food supplement, Mn‐Thr appears to be a promising enteric contrast agent for MRI.     

In vivo carotid plaque MRI using quantitative T2* measurements with ultrasmall superparamagnetic iron oxide particles: a dose-response study to statin therapy

This study investigates T₂* quantification in carotid plaques before and after the administration of ultrasmall superparamagnetic iron oxide particles (USPIOs) in a cohort of patients receiving statin therapy. Phantom studies were performed using gels with varying concentrations of USPIOs. In the phantom study, 12 gels were prepared with a range of freely distributed concentrations of USPIO nanoparticles (0–0.05 mg/mL). Relative signal intensity measurements were obtained from a T₂*‐weighted sequence as well as quantitative T₂* (qT₂*) measurements. In the patient study, 40 patients with >40% carotid stenosis were randomised to low‐ and high‐dose statin therapy (10 and 80 mg of atorvastatin). Pre‐ and post‐ (36 h) USPIO‐enhanced MRI were performed at baseline, and at 6 and 12 weeks. A linear mixed‐effects model was applied to account for the inherent correlation of multiple‐plaque measurements from the same patient and to assess dose–response differences to statin therapy. In the phantom study, the T₂*‐weighted sequence demonstrated an initial increase (T₁ effect), followed by a decrease (T₂* effect), in relative signal intensity with increasing concentrations of USPIO. The qT₂* values decreased exponentially with increasing concentrations of USPIO. In the patient study, there was a highly significant difference in post‐USPIO T₂* measurements in plaques between the low‐ and high‐dose statin groups. This was observed for both the difference in qT₂* measurements (post‐USPIO minus pre‐USPIO) (p < 0.001) and for qT₂* post‐USPIO only (p < 0.001). The post‐USPIO qT₂* values were as follows: baseline: low dose, 13.6 ± 5.5 ms; high dose, 12.9 ± 6.2 ms; 6 weeks: low dose, 13.3 ± 6.7 ms; high dose, 14.3 ± 7.7 ms; 12 weeks: low dose, 14.0 ± 7.6 ms; high dose, 18.3 ± 11.2 ms. It can be concluded that qT₂* measurements provide an alternative method of quantifying USPIO uptake. These results also demonstrate that changes in USPIO uptake can be measured using post‐USPIO imaging only. Copyright © 2010 John Wiley & Sons, Ltd.     

Fast screening of paramagnetic molecules in zebrafish embryos by MRI

Zebrafish embryo is a well-established model used in many fields of modern experimental biology. We demonstrate that it provides a promising model platform for exploring fundamental MR aspects that can be used to screen and study active MR molecules before progressing to more complex living systems. Setting up a dedicated MRI methodology, we arrayed a large number of living embryos, which were microinjected at very early stages of development with different contrast agents. We also showed that MRI signal intensity correlates with the gadolinium content of zebrafish embryos. This allowed us to validate a new approach for MR compound screening. Using a specific surface coil of 5 mm inner diameter, we obtained for the first time high-spatial-resolution images at 7 T of living zebrafish embryos with a 47 microm isotropic voxel size with an acquisition time of 39 min. Finally, we discuss potential applications of this development: a viable in vivo assay for screening small pharmacological compounds; assessment of and tracking the action of molecules over time. Exploring in vivo biological activity, gene function analysis, and detailed characterization of disease processes in fish are natural extensions of these preliminary studies.     

中枢神经系统血管母细胞瘤MRI特点分析

目的 进一步提高对中枢神经系统血管母细胞瘤MRI特点的认识。方法 搜集经手术病理证实的中枢神经系统血管母细胞瘤21例，对其MRI表现进行回顾性分析。结果 血管母细胞瘤常见于后颅窝，发生于椎管内者少见。本组21例23个病灶，大囊小结节型9例，实质型10例，单纯囊型2例。血管母细胞瘤典型表现为大囊、小结节且结节显著异常强化。实质型MRI特征性不强，术前误诊率高达70％，尤其脊髓内实质型，术前MRI正确诊断率仅为20％。结论 MRI是诊断血管母细胞瘤的有效检查方法，MRI增强对于血管母细胞瘤的正确诊断和分型尤为重要。     

The distribution of Mn2+ in rabbit eyes after topical administration for manganese-enhanced MRI

Purpose: To analyze the distribution of Mn²⁺ in rabbit eyes after topical administration of Mncl₂ for manganese-enhanced MRI. Methods: Forty-eight Chinese white rabbits were divided into three groups. In group 1 (n = 4), the baseline concentration of Mn²⁺ in aqueous, vitreous and serum samples were analyzed. In group 2 and 3, the rabbits received one topical instillation (20 μL) of Mncl₂ (1 mol•L^-1). In group 2 (n = 40), aqueous, vitreous and serum samples were collected and analyzed at predetermined time points (0.5, 1, 2, 4, 6, 12, 24, 48, 72 and 168 hours postdose). Assays were performed using inductively coupled plasma-mass spectrometer (ICP-MS). In group 3 (n = 4), after topical administration of Mncl₂, dynamic manganese-enhanced MRI (MEMRI) was performed at predetermined time points. The signal-to-noise ratio (SNR) was calculated to evaluate the enhancements of eyes. Results: After topical administration, the maximum concentrations of Mn²⁺ in the aqueous and vitreous samples were 11.1641 ± 0.7202 (2 hours) and 1.5622 ± 0.1567 (12 hours). In group 3, the maximum enhancement of aqueous humor (SNR = 108.81 ± 10.65) appeared at 2 hours postdose, whereas, no significant changes were detected in vitreous. Conclusion: Mn²⁺ could distribute into aqueous humor rapidly after topical administration of Mncl₂, whereas, the concentration of Mn²⁺ in vitreous body fluctuated in a narrow range over the course. The uptake of Mn²⁺ in retina may involve several different pathways.     

Monitoring dynamic alterations in calcium homeostasis by T (1)-weighted and T (1)-mapping cardiac manganese-enhanced MRI in a murine myocardial infarction model

Manganese has been used as a T(1)-weighted MRI contrast agent in a variety of applications. Because manganese ions (Mn(2+)) enter viable myocardial cells via voltage-gated Ca(2+) channels, manganese-enhanced MRI is sensitive to the viability and inotropic state of the heart. In spite of the established importance of Ca(2+) regulation in the heart both before and after myocardial injury, monitoring strategies to assess Ca(2+) homeostasis in affected cardiac tissues are limited. This study implements a T(1)-mapping method to obtain quantitative information both dynamically and over a range of MnCl(2) infusion doses. To optimize the current Mn(2+) infusion protocols, we performed both dose-dependent and temporal washout studies. A non-linear relationship between infused MnCl(2) solution dose and increase in left ventricular wall relaxation rate (DeltaR(1)) was observed. Control mice also exhibited significant Mn(2+) clearance over time, with a decrease in DeltaR(1) of approximately 50% occurring in just 2.5 h. The complicated efflux time dependence possibly suggests multiple efflux mechanisms. With the use of the measured relationship between infused Mn(2+) dose, DeltaR(1), and inductively coupled plasma mass spectrometry data analysis provided a means of estimating the absolute heart Mn concentration in vivo. We show that this technique has the sensitivity to observe or monitor potential alterations in Ca(2+) handling in vivo because of the physiological remodeling after myocardial infarction. Left ventricular free wall DeltaR(1) values were significantly lower (P = 0.005) in the adjacent zone, surrounding the injured myocardial tissue, than in healthy tissue. This inferred reduction in Mn concentration can be used to estimate potentially salvageable myocardium in vivo for future treatment or evaluation of disease progression.     

Longitudinal manganese-enhanced magnetic resonance imaging of neural projections and activity

Manganese-enhanced magnetic resonance imaging (MEMRI) holds exceptional promise for preclinical studies of brain-wide physiology in awake-behaving animals. The objectives of this review are to update the current information regarding MEMRI and to inform new investigators as to its potential. Mn(II) is a powerful contrast agent for two main reasons: (1) high signal intensity at low doses; and (2) biological interactions, such as projection tracing and neural activity mapping via entry into electrically active neurons in the living brain. High-spin Mn(II) reduces the relaxation time of water protons: at Mn(II) concentrations typically encountered in MEMRI, robust hyperintensity is obtained without adverse effects. By selectively entering neurons through voltage-gated calcium channels, Mn(II) highlights active neurons. Safe doses may be repeated over weeks to allow for longitudinal imaging of brain-wide dynamics in the same individual across time. When delivered by stereotactic intracerebral injection, Mn(II) enters active neurons at the injection site and then travels inside axons for long distances, tracing neuronal projection anatomy. Rates of axonal transport within the brain were measured for the first time in “time-lapse” MEMRI. When delivered systemically, Mn(II) enters active neurons throughout the brain via voltage-sensitive calcium channels and clears slowly. Thus behavior can be monitored during Mn(II) uptake and hyperintense signals due to Mn(II) uptake captured retrospectively, allowing pairing of behavior with neural activity maps for the first time. Here we review critical information gained from MEMRI projection mapping about human neuropsychological disorders. We then discuss results from neural activity mapping from systemic Mn(II) imaged longitudinally that have illuminated development of the tonotopic map in the inferior colliculus as well as brain-wide responses to acute threat and how it evolves over time. MEMRI posed specific challenges for image data analysis that have recently been transcended. We predict a bright future for longitudinal MEMRI in pursuit of solutions to the brain-behavior mystery.     

Identification of intracranial liqor metastases of experimental stereotactically implanted brain tumors by the tumor-selective MRI contrast agent MnTPPS

Two cases of stereotactically induced and spontaneously metastasizing neoplasms in the rat and the cat brain are reported. In the rat, a malignant Schwannoma derived from initially supratentorially implanted RN6 cells developed a second tumor in the posterior cranial fossa. In the cat, a highly malignant polymorphous anaplastic glioma induced by implantation of cloned rat glioma cells (F98) into the left internal capsule developed small tumor cell nests along the ependyma of the ipsilateral ventricle. In precontrast magnetic resonance imaging (MRI) of both cases, the primary tumor was detectable only by a very weak hypointensity and through a shift of the midline. No metastases were apparent. Application of the metallated paramagnetic porphyrin derivative manganese(III) tetraphenylporphine sulfonate (MnTPPS) resulted in a remarkable contrast enhancement between tumoral and normal tissue, which was evident not only in the primary tumor but also in the small metastases. These observations demonstrate for the first time that MnTPPS is an efficient MRI contrast agent for the detection of metastases from primary brain neoplasms and, in consequence, support the hypothesis of its selective binding to tumor cells.     

The brain mapping of the retrieval of conditioned taste aversion memory using manganese-enhanced magnetic resonance imaging in rats

Manganese-enhanced MRI (MEMRI) is a newly developed noninvasive imaging technique of brain activities. The signal intensity of MEMRI reflects cumulative activities of the neurons. To validate the use of MEMRI technique to investigate the neural mechanisms of learning and memory, we tried to map brain areas involved in the retrieval of conditioned taste aversion (CTA) memory. CTAs were established to saccharin (conditioned stimulus: CS) by pairing its ingestion with an i.p. injection of LiCl (unconditioned stimulus: US). LiCl solutions (as a robust aversion chemical) of 0.15 M were injected i.p. 15 min after drinking the saccharine solution (CS). After the two times conditionings, these rats showed a robust aversion to the saccharine solution (CS). Rats of the control group were injected saline i.p. instead of LiCl solutions. The MRI signal intensities at the gustatory cortex (GC), the core subregion of the nucleus accumbens (NAcC), the shell subregion of the nucleus accumbens (NAcSh), the ventral pallidum (VP), the central nucleus of amygdala (CeA), the lateral hypothalamus (LH), and the basolateral nucleus of amygdala (BLA) of the conditioned group were higher than those of the control group. There were no significant differences between the conditioned and the control groups in the intensities for other regions, such as the striatum area, motor cortex, cingulate cortex, interstitial nucleus of the posterior limb of the anterior commissure and hippocampus. These indicate that the GC, NAcC, NAcSh, VP, CeA, LH and BLA have important roles in the memory retrieval of CTA.     

Manganese‐enhanced MRI (ME MRI) in evaluation of the auditory pathway in an experimental rat model

This study aimed to explore the optimal dose and manner of administration for visualization of the auditory pathway on manganese‐enhanced MRI (ME MRI). Twenty‐four healthy male Sprague–Dawley rats were randomly divided into three experimental groups (n = 8 for Groups A, B and C). The rats in Groups A, B and C were subjected to MnCl₂ injection through the tympanum, inner ear endolymph and perilymph, respectively (0.2 M for four rats and 0.4 M for the others in each group) and observed at 1, 2, 3, 4, 7 and 10 days after the operation with 3.0 T MRI. The signal intensity (SI) and dynamic changes of the auditory pathways at various times, and at two doses through three injection routes, were compared by statistical analysis. Administration of MnCl₂ through the perilymph best showed the complete auditory pathway (P < 0.01), whereas administration though the tympanum only demonstrated part of the pathway. The SI was highest at 24 h after administration of the tracer and began to decline at 48 h. The SI of the auditory cortex was higher after the injection of 0.4 M MnCl₂ than that of 0.2 M MnCl₂. ME MRI best demonstrated the whole auditory pathway at 24 h after the injection of 0.4 M MnCl₂ through the perilymph in the rat, which provided an optimal method for the study of ME MRI of the auditory pathway in the animal model.     

Current status of functional MRI on small animals: application to physiology, pathophysiology, and cognition

This review aims to make the reader aware of the potential of functional MRI (fMRI) in brain activation studies in small animal models. As small animals generally require anaesthesia for immobilization during MRI protocols, this is believed to be a serious limitation to the type of question that can be addressed with fMRI. We intend to introduce a fresh view with an in-depth overview of the surprising number of fMRI applications in a wide range of important research domains in neuroscience. These include the pathophysiology of brain functioning, the basic science of activity, and functional connectivity of different sensory circuits, including sensory brain mapping, the challenges when studying the hypothalamus as the major control centre in the central nervous system, and the limbic system as neural substrate for emotions and reward. Finally the contribution of small animal fMRI research to cognitive neuroscience is outlined. This review avoids focusing exclusively on traditional small laboratory animals such as rodents, but rather aims to broaden the scope by introducing alternative lissencephalic animal models such as songbirds and fish, as these are not yet well recognized as neuroimaging study subjects. These models are well established in many other neuroscience disciplines, and this review will show that their investigation with in vivo imaging tools will open new doors to cognitive neuroscience and the study of the autonomous nervous system in experimental animals.     

Quantitative measurement of spinal cord blood volume in humans using vascular-space-occupancy MRI

Although perfusion is of major interest for many spinal cord disorders, there is no established, reproducible technique for evaluating blood flow or blood volume of the spinal cord in humans. Here the first report of in vivo measurement of human spinal cord blood volume (scBV) is presented. An FDA-approved contrast agent, Gd-DTPA, was used as an intravascular agent for the cord parenchyma, and pre-/post-contrast vascular-space-occupancy (VASO) MRI experiments were performed to obtain a quantitative estimation of scBV in mL blood/100 mL tissue. VASO MRI was used because it does not rely on knowledge of an arterial input function, it avoids the imaging artifacts of single-shot echo planar imaging approaches, and it requires only relatively simple and direct calculations for scBV quantification. Preliminary tests at 1.5 T and 3 T gave mean +/- SD scBV values of 4.3 +/- 0.7 ml/100 mL tissue (n = 6) and 4.4 +/- 0.7 ml/100 mL tissue (n = 4), respectively, consistent with the expectation that the scBV values would not be field-dependent.     

Testing the calcium hypothesis of aging in the rat hippocampus in vivo using manganese-enhanced MRI

In this study, we noninvasively tested the hypothesis that Mn²⁺-enhanced magnetic resonance imaging (MEMRI) is sensitive to age-related changes in Ca²⁺ influx occurring in the hippocampal region CA1. Uptake of Mn²⁺, an MRI contrast agent and Ca²⁺ surrogate with low cellular efflux rates (days to weeks), was measured in longitudinal MEMRI studies involving 2 separate groups of male Long-Evans rats: one group was studied at 2.5 and 7 months of age, whereas the other was studied at 7 and 19 months of age. Separate or combined analysis revealed that the extent of Mn²⁺ accumulation in CA1 significantly increased with age (p < 0.05). These results provide first-time in vivo confirmation of the calcium hypothesis of aging and justify future longitudinal studies combining MEMRI with behavioral testing to investigate mechanisms of age-related cognitive decline.     

Influence of pain anticipation on brain activity and pain perception in Gulf War Veterans with chronic musculoskeletal pain

Anticipation of a painful experience can influence brain activity and increase sensitivity to experimental somatosensory stimuli in healthy adults, but this response is poorly understood among individuals with chronic musculoskeletal pain (CMP). Studies of brain and perceptual responses to somatosensory stimuli are used to make inferences about central nervous system dysfunction as a potential mechanism of symptoms. As such, we sought to (a) determine the influence of pain anticipation on pain‐relevant brain regions and pain perception, and (b) characterize potential differences in these responses between Gulf War Veterans with CMP and matched healthy control (CO) Veterans. CMP (N = 30) and CO Veterans (N = 31) were randomized to conditions designed to generate expectations that either painful (pain) or nonpainful (no pain) stimuli would be administered. Brain responses to five nonpainful thermal stimuli were measured during fMRI, and each stimulus was rated for pain intensity and unpleasantness. In the pain condition, an incremental linear decrease in activity across stimuli was observed in the posterior cingulate cortex, cingulate cortex, and middle temporal gyrus. Further, in the pain condition, differential responses were observed between CMP and CO Veterans in the middle temporal gyrus. These findings indicate that brain responses to nonpainful thermal stimuli in Veterans with CMP are sensitive to pain anticipation, and we recommend accounting for the influence of pain anticipation in future investigations of central nervous system dysfunction in CMP.     

Primary central nervous system B cell lymphoma with features intermediate between diffuse large B cell lymphoma and Burkitt lymphoma

B cell lymphoma with features intermediate between diffuse large B cell lymphoma and Burkitt lymphoma (DLBCL/BL) is a new lymphoma entity which is recognized in the current World Health Organization (WHO) classification (2008). We report a case of a primary central nervous system lymphoma (PCNSL) with findings consistent with DLBCL/BL. It is characterized by a very aggressive clinical course, and a widespread multifocal involvement of the CNS. Our case shows that a DLBCL/BL can manifest in the CNS alone without any systemic involvement.     

Water signal attenuation by D2O infusion as a novel contrast mechanism for 1H perfusion MRI

Deuterium oxide (D₂O), which is commercially available and nonradioactive, was proposed as a perfusion tracer before the clinical usage of conventional gadolinium‐based MRI contrast agents. However, the sensitivity of direct deuterium detection is the major challenge for its application. In this study, we propose a contrast‐enhanced strategy to indirectly trace administered D₂O by monitoring the signal attenuation of ¹H MRI. Experiments on D₂O concentration phantoms and in vivo rat brains were conducted to prove the concept of the proposed contrast mechanism. An average maximum signal drop ratio of 5.25 ± 0.91% was detected on ¹H MR images of rat brains with 2 mL of D₂O administered per 100 g of body weight. As a diffusible tracer for perfusion, D₂O infusion is a practicable method for the assessment of tissue perfusion and has the potential to provide different information from gadolinium‐based contrast agents, which have limited permeability for blood vessels. Furthermore, the observed negative relaxivities of D₂O reveal the ¹H–D exchange effect. Therefore, applications of perfusion MRI with D₂O as a contrast agent are worthy of further investigation. Copyright © 2013 John Wiley & Sons, Ltd.     

Reflex changes in the urinary bladder after mechanical and thermal stimulation of the skin at various segmental levels in cats

Mechanical or thermal stimulation of various skin areas produced reflex changes in the urinary bladder in anesthetized cats. When the bladder was quiescent, mechanical or thermal stimulation of the skin resulted in a reflex increase in the tonus of the bladder only when the perineal area was stimulated. This cutaneo-vesical excitatory reflex was a spinal reflex with its efferent arc in the pelvic nerves. When there were spontaneous, large, rhythmic micturition contractions of the bladder at a frequency of 1–3/min, these contractions were usually inhibited by mechanical or thermal stimulation of the skin of the perineum, abdomen or chest in this order of effectiveness. Sometimes, the inhibition was followed by a subsequent excitation. The efferent arc for this reflex inhibition of the large micturition contractions was also in the pelvic nerves. For both the excitatory and the inhibitory cutaneo-vesical reflex responses, noxious stimulation was much more effective than nonnoxious stimulation.     

Phosphorylation status of heat shock protein 27 regulates the interleukin-1β-induced interleukin-6 synthesis in C6 glioma cells

Heat shock protein 27 (HSP27), a low-molecular-weight HSP, is recognized as a molecular chaperone. In response to various stimuli, HSP27 expression is induced in the CNS. However, the exact roles of HSP27 in the CNS have not yet been clarified. It has been reported that interleukin (IL)-1β stimulates IL-6 synthesis in C6 glioma cells. In the present study, we investigated the role of HSP27 in the IL-1β-induced IL-6 synthesis in C6 cells. IL-1β alone did not affect the levels of HSP27. The IL-1β-induced IL-6 release in HSP27-downregulated C6 cells were enhanced compared with those in control siRNA-transfected cells. On the other hand, the IL-1β-induced IL-6 release was significantly enhanced in C6 cells transfected with HSP27 than those in control cells in time- and dose-dependent manner. The IL-1β-induced IL-6 release and the mRNA expression were markedly suppressed in C6 cells transfected with phosphorylated HSP27, while those in the cells transfected with unphosphorylated HSP27 were enhanced. In conclusion, these results strongly suggest that phosphorylated status of HSP27 has a switching role in the IL-1β-induced IL-6 synthesis in C6 glioma cells.