Project description:To identify putative genes that could contribute to the phenotypic plasticity of TRPV1 nociceptors in inflammation-induced sensitization, we used the Complete Freund’s Adjuvant (CFA) model of chronic inflammatory pain. Three days post intraplantar injection of CFA, ipsilateral and contralateral lumbar DRG neurons were separated, and TRPV1-pHluorin neurons were purified by FACS and analyzed through the GeneChip™ Mouse Gene 2.0 ST Array. The array analysis provided a complete expression profile of mRNA between contralateral and ipsilateral TRPV1 neurons following inflammatory insult. In inflammatory condition, we found >100 genes to be up or down regulated in TRPV1 neurons.
Project description:The anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase known for its oncogenic potential that is involved in the development of the peripheral and central nervous system. ALK receptor ligands ALKAL1 and ALKAL2 were recently found to promote neuronal differentiation and survival. Here, we show that inflammation or injury enhanced ALKAL2 expression in a subset of TRPV1+ sensory neurons. Notably, ALKAL2 was particularly enriched in both mouse and human peptidergic nociceptors, yet weakly expressed in nonpeptidergic, large-diameter myelinated neurons or in the brain. Using a coculture expression system, we found that nociceptors exposed to ALKAL2 exhibited heightened excitability and neurite outgrowth. Intraplantar CFA or intrathecal infusion of recombinant ALKAL2 led to ALK phosphorylation in the lumbar dorsal horn of the spinal cord. Finally, depletion of ALKAL2 in dorsal root ganglia or blocking ALK with clinically available compounds crizotinib or lorlatinib reversed thermal hyperalgesia and mechanical allodynia induced by inflammation or nerve injury, respectively. Overall, our work uncovers the ALKAL2/ALK signaling axis as a central regulator of nociceptor-induced sensitization. We propose that clinically approved ALK inhibitors used for non-small cell lung cancer and neuroblastomas could be repurposed to treat persistent pain conditions.
Project description:Objective – Following destabilization of the medial meniscus (DMM), mice develop experimental osteoarthritis (OA) and associated pain behaviors that are dependent on the stage of disease. We aimed to describe changes in gene expression in knee-innervating dorsal root ganglia (DRG) after surgery, in order to identify molecular pathways associated with three pre-defined pain phenotypes: “post-surgical pain”, “early-stage OA pain”, and “persistent OA pain”. Design – We performed DMM or sham surgery in 10-week old male C57BL/6 mice and harvested L3-L5 DRG 4, 8, and 16 weeks after surgery or from age-matched naïve mice (n=3/group). RNA was extracted and an Affymetrix Mouse Transcriptome Array 1.0 was performed. Three pain phenotypes were defined: “post-surgical pain” (sham and DMM 4-week vs. 14-week old naïve), “early OA pain” (DMM 4-week vs. sham 4-week), and “persistent OA pain” (DMM 8- and 16-week vs. naïve and sham 8- and 16-week). ‘Top hit’ genes were defined as p<0.001. Pathway analysis (Ingenuity Pathway Analysis) was conducted using differentially expressed genes defined as p<0.05. In addition, we performed qPCR for Ngf and immunohistochemistry for F4/80+ macrophages in the DRG. Results – For each phenotype, top hit genes identified a small number of differentially expressed genes, some of which have been previously associated with pain (7/67 for “post-surgical pain”; 2/14 for “early OA pain”; 8/37 for “persistent OA pain”). Overlap between groups was limited, with 8 genes differentially regulated (p<0.05) in all three phenotypes. Pathway analysis showed that in the persistent OA pain phase many of the functions of differentially regulated genes are related to immune cell recruitment and activation. Genes previously linked to OA pain (CX3CL1, CCL2, TLR1, and NGF) were upregulated in this phenotype and contributed to activation of the neuroinflammation canonical pathway. In separate sets of mice, we confirmed that Ngf was elevated in the DRG 8 weeks after DMM (p=0.03), and numbers of F4/80+ macrophages were increased 16 weeks after DMM (p=0.002 vs. Sham). Conclusion- These transcriptomics findings support the idea that distinct molecular pathways discriminate early from persistent OA pain. Pathway analysis suggests neuroimmune interactions in the DRG contribute to initiation and maintenance of pain in OA. We grouped samples based on pain phenotype in the DMM mouse model of osteoarthritis. Group 1: post-surgical pain (DMM and sham +4 week samples); Group 2: post-surgical control (Naïve +4 week samples); Group 3: Early osteoarthritis pain (DMM +4 week samples); Group 4: Early controls (sham+4 and naive+4 week samples); Group 5: Persistent pain (DMM+8 and DMM+16 week samples); Group 6: Persistent controls (sham+8, naive+8, sham+16, and naive +16 samples). We compared Group 1 vs Group 2; Group 3 vs Group 4; and Group 5 vs Group 6 to draw the conclusions presented in our manuscript.
Project description:To investigate the different mechanism of Formalin induced acute pain and CFA induced persistent pain in mPFC and BNST, mice were treated by Formalin exposure or CFA exposure or without treatment and their mPFC and BNST were dissected to perform RNA seq.
Project description:Shared transcriptomic and epigenetic changes in two animal models improves our understanding of how chromatin structural changes alter dorsal root ganglion (DRG) gene expression under persistent pain conditions.
Project description:Fms-like tyrosine kinase 3 (Flt3) is a regulator of hematopoietic progenitor cells. It is a target of tyrosine kinase inhibitors (TKIs) used for acute myeloid leukemia treatment. Flt3 and its ligand (Flt3L) are expressed in the heart and cardiac side effects occur under Flt3-targeting TKIs. Whether Flt3/Flt3L also regulate cardiac progenitor cells (CPCs), however, is not known. The cardiac side population (SP) is a pool of heterogenous CPCs that can give rise to all cardiac lineages, hence contributing to cardiovascular homeostasis. Here we show that SP-CPCs produce and are responsive to Flt3L. Compared to wild-type, SP-CPCs from flt3L-/- mice are less abundant, with less contribution of CD45-CD34+ cells, and lower expression of gene sets related to epithelial-to-mesenchymal transition, cardiovascular development and stem cell differentiation. Upon culturing and compared to wild-type, flt3L-/- Sca1+CD31- SP-CPCs show increased proliferation and less vasculogenic commitment, but differentiation can be induced in the presence of receptor tyrosine kinase-activating growth factors. The observed differences are associated with decreased microvascularisation and global systolic function of flt3L-/- hearts. Thus, Flt3 contributes to a receptor tyrosine kinase signature necessary for the maintenance and functionality of SP-CPCs. These findings have potential implications regarding cardiovascular side effects observed under TKI therapy.
Project description:Mutations or amplifications of receptor tyrosine kinases (RTKs) are common in many cancers. Given the emergence of small molecule inhibitors specific to RTKs, these signalling cascades are attractive therapeutic targets. However, compensatory and adaptation mechanisms limit the clinical utility of compounds that target nodes in RTK networks. Here we show that PHLDA1 down-regulation is critical to acquisition and maintenance of drug resistance in RTK-driven cancer.
Project description:Insulin acts through the insulin receptor (IR) tyrosine kinase to exert its classical metabolic and mitogenic actions. Here, using receptors with either short or long deletion of the β-subunit or mutation of the kinase active site (K1030R), we uncover a second novel IR signaling pathway that is intracellular domain dependent, but ligand and tyrosine kinase-independent (LYK-I). These LYK-I actions of the IR are linked to changes in phosphorylation of a network of proteins involved in the regulation of extracellular matrix organization, cell cycle, ATM signaling and cellular senescence; and result in upregulation of expression of multiple extracellular matrix-related genes and proteins, down-regulation of immune/interferon-related genes and proteins, and increased sensitivity to apoptosis. Thus, in addition to classical ligand and tyrosine kinase-dependent (LYK-D) signaling, the IR regulates a second, novel ligand and tyrosine kinase-independent (LYK-I) pathway which regulates the cellular machinery involved in senescence, matrix interaction and response to extrinsic challenges.
Project description:Identification of germinal center (GC) B cells is typically reliant on the use of surface activation markers that exhibit a wide range of expression. Here we identify Ephrin-B1, a ligand for Eph-related receptor tyrosine kinases, as a specific marker of mature GC B cells. The number of Ephrin-B1+ GC B cells increases during the course of an immune response with Ephrin-B1+ GC B cells displaying elevated levels of Bcl6, S1pr2, and Aicda relative to their Ephrin-B1– counterparts. We further identified a small proportion of recently dividing, somatically mutated Ephrin-B1+ GC B cells that have begun to downregulate Bcl6 and S1pr2 and express markers associated with memory B cells such as CD38 and EBI2. Transcriptional analysis indicates that these cells are developmentally related to memory B cells, and likely represent a population of GC memory precursor (PreMem) B cells. GC PreMem cells display enhanced survival relative to bulk GC B cells, localize near the edge of the GC and are predominantly found within the light zone. These findings offer insight into the significant heterogeneity that exists within the GC B cell population and provide tools to further dissect signals regulating the differentiation of GC B cells.