Up-regulation of platelet-activating factor synthases and its receptor in spinal cord contribute to development of neuropathic pain following peripheral nerve injury

<p>Abstract</p> <p>Background</p> <p>Platelet-activating factor (PAF; 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine) is a lipid mediator derived from cell membrane. It has been reported that PAF is involved in various pathological conditions, such as spinal cord injury, multiple sclerosis, neuropathic pain and intrathecal administration of PAF leads to tactile allodynia. However, the expression of PAF synthases and its receptor in the spinal cord following peripheral nerve injury is unknown.</p> <p>Methods</p> <p>Using the rat spared nerve injury (SNI) model, we investigated the expression of PAF synthases (LPCAT1 and 2) and PAF receptor (PAFr) mRNAs in the spinal cord. Reverse transcription polymerase chain reaction (RT-PCR) and double-labeling analysis of <it>in situ </it>hybridization histochemistry (ISHH) with immunohistochemistry (IHC) were employed for the analyses. Pain behaviors were also examined with PAFr antagonist (WEB2086).</p> <p>Results</p> <p>RT-PCR showed that LPCAT2 mRNA was increased in the ipsilateral spinal cord after injury, but not LPCAT1 mRNA. Double-labeling of ISHH with IHC revealed that LPCAT1 and 2 mRNAs were constitutively expressed by a subset of neurons, and LPCAT2 mRNA was increased in spinal microglia after nerve injury. RT-PCR showed that PAFr mRNA was dramatically increased in the ipsilateral spinal cord after nerve injury. Double-labeling analysis of ISHH with IHC revealed that after injury PAFr mRNA was predominantly colocalized with microglia in the spinal cord. Continuous intrathecal administration of the PAFr antagonist suppressed mechanical allodynia following peripheral nerve injury. Delayed administration of a PAFr antagonist did not reverse the mechanical allodynia.</p> <p>Conclusions</p> <p>Our data show the histological localization of PAF synthases and its receptor in the spinal cord following peripheral nerve injury, and suggest that PAF/PAFr signaling in the spinal cord acts in an autocrine or paracrine manner among the activated microglia and neurons, thus contributing to development of neuropathic pain.</p

Orchestrated ensemble activities constitute a hippocampal memory engram

The brain stores and recalls memories through a set of neurons, termed engram cells. However, it is unclear how these cells are organized to constitute a corresponding memory trace. We established a unique imaging system that combines Ca2+ imaging and engram identification to extract the characteristics of engram activity by visualizing and discriminating between engram and non-engram cells. Here, we show that engram cells detected in the hippocampus display higher repetitive activity than non-engram cells during novel context learning. The total activity pattern of the engram cells during learning is stable across post-learning memory processing. Within a single engram population, we detected several sub-ensembles composed of neurons collectively activated during learning. Some sub-ensembles preferentially reappear during post-learning sleep, and these replayed sub-ensembles are more likely to be reactivated during retrieval. These results indicate that sub-ensembles represent distinct pieces of information, which are then orchestrated to constitute an entire memory

Assessment of Macrovascular Invasion in Advanced Hepatocellular Carcinoma: Clinical Implications and Treatment Outcomes with Systemic Therapy

Introduction: Macrovascular invasion (MVI) is a strong prognostic factor for advanced hepatocellular carcinoma (HCC). The current criteria for radiological assessment are unclear in evaluating the impact of MVI on systemic therapy. In this study, we standardized the assessment of MVI and validated its clinical relevance. Methods: Clinical data were collected from patients with advanced HCC and MVI who received first-line systemic therapy at four medical centers in Japan. First, we used macrovascular invasion progression disease (MVI-PD) to track MVI progression, and Response Evaluation Criteria in Solid Tumours version 1.1 progression disease (RECIST v1.1-PD) to evaluate tumor enlargement other than MVI and the appearance of new lesions. Next, we assessed the prognostic value of MVI-PD and RECIST v1.1-PD. Results: Of the 207 advanced HCC patients with MVI, 189 received appropriate imaging evaluation. 40 (21.2%) patients had MVI-PD and RECIST v1.1-PD, 51 (27.0%) had prior MVI-PD, and 61 (32.3%) had prior RECIST v1.1-PD. In a landmark analysis, the prognosis of 163 patients who survived more than three months was analyzed based on the assessment of imaging response during the first three months. The median overall survival (OS) was 5.4 months in those who had MVI-PD and RECIST v1.1-PD, 7.4 months in those who had RECIST v1.1-PD only, 7.2 months in those who had MVI-PD only, and 19.7 months in patients who had neither (p&lt;0.001). The correlation coefficients between progression-free survival and OS in patients with appropriate imaging assessments were similar for MVI-PD (0.515) and RECIST v1.1-PD (0.498). Conclusion: Our findings demonstrate the link between MVI progression and poor OS in systemic therapy for advanced HCC, emphasizing the importance of an accurate method for assessing MVI progression