Gray Matter Volume Abnormality in Chronic Pain Patients With Depressive Symptoms: A Systemic Review and Meta-Analysis of Voxel-Based Morphometry Studies.

Background: Gray matter volume (GMV) alteration in specific brain regions has been widely regarded as one of the most important neuroplasticity features in chronic pain patients with depressive symptoms (CP-D). However, the consistent and significant results were still lacking. Thus, further exploration was suggested to be performed. Objectives: This study aimed to comprehensively collect the voxel-based morphometry (VBM) studies on GMV alteration between CP-D and healthy controls (HCs). And a systemic review and meta-analysis were made to explore the characteristic brain regions in chronic pain and depression comorbidity. Methods: Search of PubMed, MEDLINE, Web of Science, and Cochrane Library databases updated to July 13, 2021. The altered GMV between CP-D and HCs in VBM studies was included in this meta-analysis. In total, 18 studies (20 datasets) and 1320 participants (520 patients and 800 HCs) were included. The significant coordinate information (x, y, z) reported in standard space and the effect size (t-value or z-score) were extracted and analyzed by anisotropic effect size-signed differential mapping (AES-SDM) 5.15 software. Results: According to the main analysis results, CP-D showed significant and consistent increased GMV in the left hippocampus (HIP. L) and decreased GMV in the medial part of the left superior frontal gyrus (SFG. L, BA 10) compared to HCs. Subgroup analysis showed significant decreased GMV in the medial orbital part of SFG.R (BA 10) in neuropathic pain, as well as significant increased GMV in the right parahippocampal gyrus (PHG.R, BA 35), left hippocampus (HIP.L, BA 20), and right middle frontal gyrus (MFG.R) in musculoskeletal pain. Furthermore, meta-regression showed a positive relationship between the decreased GMV in the medial part of SFG.L and the percentage of female patients. Conclusion: GMV abnormality in specific brain areas (e.g., HIP.L and SFG) was robust and reproducible, which could be significantly involved in this comorbidity disease. The findings in this study may be a valuable reference for future research. Systematic Review Registration: [www.crd.york.ac.uk/prospero/].

The synergistic effect of treatment with triptolide and MK-801 in the rat neuropathic pain model.

Triptolide (T10), an active component of Tripterygium wilfordii Hook F, is reported to have potent anti-inflammatory and analgesic effects. Additionally, MK-801, a noncompetitive N-methyl-D-aspartate receptor antagonist, can reduce glutamate toxicity and has a significant analgesic effect on chronic pain. In this study, we tested the possible synergistic analgesic ability by intrathecal administration of T10 and MK-801 for the treatment of neuropathic pain. Single T10 (3, 10, or 30 µg/kg), MK-801 (10, 30, or 90 µg/kg), or a combination of them were intrathecally administrated in rats with spinal nerve ligation. We found that single administration of T10 caused a slow-acting but long-term analgesic effect, while single administration of MK-801 caused a fast-acting but short-term effect. Administration of their combination showed obviously synergic analgesia and the 1:3 ratio of T10 to MK-801 reached the peak effect. Furthermore, application of T10 and/or MK-801 significantly inhibited the activation of microglia and astrocyte and phosphorylation of STAT3 and NR2B in the spinal dorsal horn induced by chronic neuropathic pain. Our data suggest that the combination of T10 and MK-801 may be a potentially novel strategy for treatment of neuropathic pain.

Mfn2-Mediated Preservation of Mitochondrial Function Contributes to the Protective Effects of BHAPI in Response to Ischemia.

Disturbances in intracellular iron homeostasis are associated with neuronal injury after stroke. However, exposure of cells to classical chelators may interfere with physiological iron functions. BHAPI is an iron prochelator that exerts strong iron binding capacity only under oxidative stress conditions. This study investigated the protective effects of N'-(1-(2-((4-(4,4,5,5-tetramethyl-1,2,3-dioxoborolan-2-yl)benzyl)oxy)phenyl)ethylidene (BHAPI) on an in vitro ischemia model mimicked by oxygen and glucose deprivation (OGD) in neuronal HT22 cells. The results showed that BHAPI significantly increased cell viability and decreased lactate dehydrogenase (LDH) release after OGD. BHAPI treatment also reduced apoptosis, as measured by flow cytometry, and suppressed caspase-3 activation. These protective effects were accompanied by preserved mitochondrial membrane potential (MMP), reduced mitochondrial swelling, promoted mitochondrial calcium buffering capacity, and increased mitochondrial respiration. The results of MitoTracker staining showed that BHAPI partially prevented the OGD-induced changes in mitochondrial morphology. Furthermore, BHAPI selectively increased the expression of mitochondrial dynamic protein Mfn2, with no effect on Mfn1 expression. Knockdown of Mfn2 with specific siRNA partially reversed the protective effects of BHAPI. In summary, the iron prochelator BHAPI protects HT22 cells against ischemic injury through preservation of mitochondrial function and Mfn2 signaling.

Notch signaling pathway regulates the growth and the expression of inflammatory cytokines in mouse basophils.

Basophils (BAs) are the least common granulocytes of all leukocytes, but they play an important role in orchestrating of chronic allergic inflammation. The Notch signaling pathway is a highly conserved pathway that influences cell lineage decisions and differentiation during various stages of development. However, the relationship between Notch signaling and BA remains to be elucidate. Here, we report that several Notch signaling molecules were found to be expressed in BAs. γ-secretase inhibitor (GSI) treatment increase BAs apoptosis, and suppress BAs proliferation. Furthermore, GSI reduced BAs in the S phase, with a concomitant accumulation in G1 and G2 phases. In addition, GSI also significantly down-regulated mRNA levels of cytokines IL-4, IL-6 and IL-13 induced by A23187, and this effect was dependent on MAPK pathway. Finally, IL-6 inhibition was specifically associated with ERK and IL-13 with JNK. Therefore, Notch signaling regulates BA biological function, at least partially via the modulation of MAPK.

Melatonin Suppresses Neuropathic Pain via MT2-Dependent and -Independent Pathways in Dorsal Root Ganglia Neurons of Mice.

Melatonin (Mel) and its receptors (MT1 and MT2) have a well-documented efficacy in treating different pain conditions. However, the anti-nociceptive effects of Mel and Mel receptors in neuropathic pain (NP) are poorly understood. To elucidate this process, pain behaviors were measured in a dorsal root ganglia (DRG)-friendly sciatic nerve cuffing model. We detected up-regulation of MT2 expression in the DRGs of cuff-implanted mice and its activation by the agonist 8-M-PDOT (8MP). Also, Mel attenuated the mechanical and thermal allodynia induced by cuff implantation. Immunohistochemical analysis demonstrated the expression of MT2 in the DRG neurons, while MT1 was expressed in the satellite cells. In cultured primary neurons, microarray analysis and gene knockdown experiments demonstrated that MT2 activation by 8MP or Mel suppressed calcium signaling pathways via MAPK1, which were blocked by RAR-related orphan receptor alpha (RORα) activation with a high dose of Mel. Furthermore, expression of nitric oxide synthase 1 (NOS1) was down-regulated upon Mel treatment regardless of MT2 or RORα. Application of Mel or 8MP in cuff-implanted models inhibited the activation of peptidergic neurons and neuro-inflammation in the DRGs by down-regulating c-fos, calcitonin gene-related peptide [CGRP], and tumor necrosis factor-1α [TNF-1α] and interleukin-1ß [IL-1ß]. Addition of the MT2 antagonist luzindole blocked the effects of 8MP but not those of Mel. In conclusion, only MT2 was expressed in the DRG neurons and up-regulated upon cuff implantation. The analgesic effects of Mel in cuff-implanted mice were closely associated with both MT2-dependent (MAPK-calcium channels) and MT2-independent (NOS1) pathways in the DRG.

Post-injury administration of allicin attenuates ischemic brain injury through sphingosine kinase 2: In vivo and in vitro studies.

Allicin, one of the main biologically active compounds derived from garlic, has been shown to exert various pharmacological activities and is considered to have therapeutic potential for many pathologic conditions. In the present study, we investigated the potential post-ischemic neuroprotective effects of allicin and its underlying mechanisms. Using a rat middle cerebral artery occlusion (MCAO) model, we found that intraperitoneal treatment with 50 mg/kg allicin significantly reduced brain infarct volume, attenuated cerebral edema and decreased the neurological deficit score. Allicin treatment also diminished TUNEL positive cells and inhibited the activation of caspase-3 after MCAO. These protective effects could be observed even if the administration was delayed to 6 h after injury. In addition, we evaluated the in vitro protective effects of allicin against oxygen glucose deprivation (OGD) induced neuronal injury in primary cultured cortical neurons. Allicin (50 µM) increased neuronal viability, decreased lactate dehydrogenase (LDH) release and inhibited apoptotic neuronal death after OGD. These protective effects could be observed even if the administration was delayed to 4 h after injury. Furthermore, allicin significantly increased the expression of sphingosine kinases 2 (Sphk2) both in vivo and in vitro. Pretreatment with the Sphk2 inhibitor ABC294640 partially reversed the protective effects of allicin against MCAO and OGD injury, indicating that an Sphk2-mediated mechanism was involved in allicin-induced protection in our models. The combination of findings suggests that post-injury administration of allicin has potential as a neuroprotective strategy for ischemic stroke.

Toll-like receptor 4 signaling in neurons of trigeminal ganglion contributes to nociception induced by acute pulpitis in rats.

Pain caused by acute pulpitis (AP) is a common symptom in clinical settings. However, its underlying mechanisms have largely remained unknown. Using AP model, we demonstrated that dental injury caused severe pulp inflammation with up-regulated serum IL-1ß. Assessment from head-withdrawal reflex thresholds (HWTs) and open-field test demonstrated nociceptive response at 1 day post injury. A consistent up-regulation of Toll-like receptor 4 (TLR4) in the trigeminal ganglion (TG) ipsilateral to the injured pulp was found; and downstream signaling components of TLR4, including MyD88, TRIF and NF-κB, and cytokines such as TNF-α and IL-1ß, were also increased. Retrograde labeling indicated that most TLR4 positve neuron in the TG innnervated the pulp and TLR4 immunoreactivity was mainly in the medium and small neurons. Double labeling showed that the TLR4 expressing neurons in the ipsilateral TG were TRPV1 and CGRP positive, but IB4 negative. Furthermore, blocking TLR4 by eritoran (TLR4 antagonist) in TGs of the AP model significantly down-regulated MyD88, TRIF, NF-κB, TNF-α and IL-1ß production and behavior of nociceptive response. Our findings suggest that TLR4 signaling in TG cells, particularly the peptidergic TRPV1 neurons, plays a key role in AP-induced nociception, and indicate that TLR4 signaling could be a potential therapeutic target for orofacial pain.

Inhibition of histamine receptor 3 suppresses glioblastoma tumor growth, invasion, and epithelial-to-mesenchymal transition.

Histamine receptor 3 (H3R) is expressed in various tumors and correlated with malignancy and tumor proliferation. However, the role of H3R in tumor invasion and epithelial to mesenchymal transition (EMT) remains unknown. Here, we explored the H3R in the highly invasive glioblastoma (GBM) and U87MG cells. We found that H3R mRNA and protein levels were up-regulated in the GBM and glioma cell lines compared to normal brain tissue and astrocytes. In U87MG cell line, inhibition of H3R by siRNA or the antagonist ciproxifan (CPX) suppressed proliferation, invasiveness, and the expression of EMT activators (Snail, Slug and Twist). In addition, expression of epithelial markers (E-cadherin and ZO-1) was up-regulated and expression of mesenchymal markers (vimentin and N-cadherin) was down-regulated in vitro and in vivo in a xenograft model. In addition, we also showed that inhibition of H3R by siRNA or CPX inactivated the PI3K/Akt and MEK/ERK signaling pathways, while inhibition of Akt or ERK activity with antagonists or siRNAs suppressed H3R agonist (R)-(α)-(-)- methylhistamine dihydrobromide (RAMH) mediated invasion and reorganization of cadherin-household. In conclusion, overexpression of H3R is associated with glioma progression. Inhibition of H3R leads to suppressed invasion and EMT of GBM by inactivating the PI3K/Akt and MEK/ERK pathways in gliomas.

Melatonin attenuates inflammation of acute pulpitis subjected to dental pulp injury.

Acute pulpitis (AP), one of the most common diseases in the endodontics, usually causes severe pain to the patients, which makes the search for therapeutic target of AP essential in clinic. Toll-like receptor 4 (TLR4) signaling is widely involved in the mechanism of pulp inflammation, while melatonin has been reported to have an inhibition for a various kinds of inflammation. We hereby studied whether melatonin can regulate the expression of TLR4/NF-ĸB signaling in the pulp tissue of AP and in human dental pulp cells (HDPCs). Two left dental pulps of the adult rat were drilled open to establish the AP model, and the serum levels of melatonin and pro-inflammatory cytokines, including interleukin 1ß (IL-1ß), interleukin 18 (IL-18) and tumor necrosis factor α (TNF-α), were assessed at 1, 3 and 5 d post injury. At the same time points, the expression of TLR4 signaling in the pulp was explored by quantitative real-time PCR and immunohistochemistry. The AP rats were administered an abdominal injection of melatonin to assess whether melatonin rescued AP and TLR4/NF-ĸB signaling. Dental pulp injury led to an approximately five-day period acute pulp inflammation and necrosis in the pulp and a significant up-regulation of IL-1ß, IL-18 and TNF-α in the serum. ELISA results showed that the level of melatonin in the serum decreased due to AP, while an abdominal injection of melatonin suppressed the increase in serum cytokines and the percentage of necrosis at the 5 d of the injured pulp. Consistent with the inflammation in AP rats, TLR4, NF-ĸB, TNF-α and IL-1ß in the pulp were increased post AP compared with the baseline expression. And melatonin showed an inhibition on TLR4/NF-ĸB signaling as well as IL-1ß and TNF-α production in the pulp of AP rats. Furthermore, melatonin could also regulate the expression of TLR4/NF-ĸB signaling in LPS-stimulated HDPCs. These data suggested that dental pulp injury induced AP and reduced the serum level of melatonin and that supplementation with melatonin may have a protective effect on AP by modulating TLR4/NF-ĸB signaling in the pulp and in pulp cells.

Associations of polymorphisms in histidine decarboxylase, histamine N-methyltransferase and histamine receptor H3 genes with breast cancer.

We previously found that genetic polymorphisms in gene coding for histamine H4 receptors were related to the risk and malignant degree of breast cancer. The roles of polymorphisms in other histamine-related genes, such as histidine decarboxylase (HDC), histamine N-methyltransferase (HNMT) and histamine H3 receptor (HRH3), remain unexplored. The aim of this study is to analyze the clinical associations of polymorphisms in HDC, HNMT and HRH3 with breast cancer. Two hundred and one unrelated Chinese Han breast cancer patients and 205 ethnicity-matched health controls were recruited for case-control investigation. Genomic DNA from the participants was extracted and 5 single nucleotide polymorphisms (SNPs) in HDC, HNMT and HRH3 were genotyped. We found that polymorphisms of HNMT and HRH3 were irrelevant with breast cancer in the present study. However, the T allele of rs7164386 in HDC significantly decreased the risk of breast cancer (adjusted odds ratios [ORs], 0.387; 95% confidence intervals [CIs], 0.208-0.720; P = 0.003). Furthermore, for HDC haplotypes, the CG haplotype of rs7164386-rs7182203 was more frequent among breast cancer patients (adjusted OR, 1.828; 95% CI, 1.218-2.744; P = 0.004) while the TG haplotype was more frequent among health controls (adjusted OR, 0.351; 95% CI, 0.182-0.678; P = 0.002). These findings indicated that polymorphisms of HDC gene were significantly associated with breast cancer in Chinese Han population and may be novel diagnostic or therapeutic targets for breast cancer. Further studies with larger participants worldwide are still needed for conclusion validation.

Preoperative serum CA19-9 levels is an independent prognostic factor in patients with resected hilar cholangiocarcinoma.

To investigate the appropriate cutoff point of CA19-9 for prognosis and other potential prognostic factors that may affect survival of patients with hilar cholangiocarcinoma (HC) after radical surgery. 168 patients who had undergone radical surgery for hilar cholangiocarcinoma and resultant macroscopic curative resection (R0 and R1) were discreetly selected for analyses. Categorized versions were used in univariate model to determine the appropriate cutoff point of CA19-9. CA19-9 and other clinicopathologic factors were analyzed for influence on survival by univariate and multivariate methods. The strongest univariate predictor among the categorized preoperative CA19-9 measures was CA19-9 less than 150 IU/L (P = 0.000). In univariate analysis, tumor size, Bismuth-Corlette classification, portal vein invasion, Lymph node metastasis, resection margin and preoperative CA19-9 levels were identified as significant prognostic factors. In multivariable analysis, lymph node metastasis, resection margin and preoperative CA19-9 levels were independent prognostic factors. our results demonstrated that preoperative CA19-9 levels was also an independent prognostic factor for hilar cholangiocarcinoma, and the most discriminative cutoff point of CA19-9 for prognosis proved to be at 150 U/ml.