1 3542 156 IMMUNOHISTOCHEMICAL ANALYSIS OF HISTONE H3 ACETYLATION IN THE TRIGEMINAL ROOT ENTRY ZONE IN AN ANIMAL MODEL OF TRIGEMINAL NEURALGIA. OBJECTIVE: THE TRIGEMINAL ROOT ENTRY ZONE (TREZ) IS A TRANSITIONAL ZONE BETWEEN THE CENTRAL NERVOUS SYSTEM (CNS) AND PERIPHERAL NERVOUS SYSTEM (PNS), ADJACENT TO THE BRAINSTEM. MICROVASCULAR COMPRESSION OF THE TREZ HAS BEEN CONSIDERED TO BE THE PRIMARY ETIOLOGY IN MOST CASES OF TRIGEMINAL NEURALGIA (TN), BUT WHETHER EPIGENETIC REGULATION IS INVOLVED IN THE PATHOGENESIS OF TN IS STILL UNCLEAR. THEREFORE, THIS STUDY WAS DESIGNED TO INVESTIGATE THE EPIGENETIC REGULATION OF HISTONE H3 ACETYLATION IN THE TREZ IN AN ANIMAL MODEL OF TN. METHODS: AN ANIMAL MODEL OF TN WAS ESTABLISHED, AND ADULT MALE SPRAGUE-DAWLEY RATS WERE RANDOMLY ASSIGNED TO A TN GROUP WITH TRIGEMINAL NERVE ROOT COMPRESSION, SHAM OPERATION GROUP, TN+HDACI GROUP (TN PLUS SELECTIVE HISTONE DEACETYLASE INHIBITOR INJECTION INTO THE TREZ), OR TN+VEH GROUP (TN PLUS VEHICLE INJECTION INTO THE TREZ). TO MEASURE THE LENGTH OF THE CENTRAL PORTION OF THE TREZ FROM THE JUNCTION OF THE TRIGEMINAL NERVE ROOT ENTERING THE PONS TO THE INTERFACE OF THE DOME-SHAPED CNS-PNS TRANSITIONAL ZONE, IMMUNOFLUORESCENT STAINING OF GLIA AND GLIAL NUCLEI WAS PERFORMED USING GLIAL FIBRILLARY ACIDIC PROTEIN (GFAP) ANTIBODY AND DAPI, RESPECTIVELY. TO INVESTIGATE THE ACETYLATION OF HISTONE H3 WITHIN THE TREZ IN A TN ANIMAL MODEL GROUP AND A SHAM OPERATION GROUP, LOCALIZATION OF HISTONE H3K9, H3K18, AND H3K27 ACETYLATION WAS EXAMINED VIA IMMUNOHISTOCHEMICAL STAINING METHODS. RESULTS: MEASUREMENTS OF THE CNS-PNS TRANSITIONAL ZONE IN THE TREZ REVEALED THAT THE AVERAGE LENGTH FROM THE JUNCTION OF THE TRIGEMINAL NERVE ROOT CONNECTING THE PONS TO THE GLIAL FRINGE OF THE TREZ IN THE TN GROUP WAS LONGER THAN THAT IN THE SHAM OPERATION GROUP (P < 0.05) AND THAT THE INTERFACE GRADUALLY MIGRATED DISTALLY. CELLS THAT STAINED POSITIVE FOR ACETYLATED HISTONE H3K9, H3K18, AND H3K27 WERE DISTRIBUTED AROUND BOTH SIDES OF THE BORDER OF THE CNS-PNS JUNCTION IN THE TREZ. THE RATIO OF IMMUNOREACTIVE H3K9-, H3K18- AND H3K27-POSITIVE CELLS IN THE TN GROUP WAS OBVIOUSLY HIGHER THAN THAT IN THE SHAM OPERATION GROUP ON POSTOPERATIVE DAYS 7, 14, 21, AND 28 (P < 0.05). CONCLUSIONS: THESE RESULTS SUGGESTED THAT CHRONIC COMPRESSION OF THE TRIGEMINAL NERVE ROOT MAY BE INVOLVED IN THE PATHOGENESIS OF TN IN AN ANIMAL MODEL BY INFLUENCING THE PLASTICITY OF THE CNS-PNS TRANSITIONAL ZONE AND THE LEVEL OF HISTONE ACETYLATION IN THE TREZ. 2018 2 821 37 CHARACTERIZATION OF ACETYLATION OF HISTONE H3 AT LYSINE 9 IN THE TRIGEMINAL GANGLION OF A RAT TRIGEMINAL NEURALGIA MODEL. TRIGEMINAL NEURALGIA (TN) IS A CHRONIC NEUROPATHIC PAIN DISORDER CHARACTERIZED BY SPONTANEOUS AND ELICITED PAROXYSMS OF ELECTRIC-SHOCK-LIKE OR STABBING PAIN IN A REGION OF THE FACE. THE EPIGENETIC REGULATION OF TN IS STILL OBSCURE. IN CURRENT STUDY, A RAT TN MODEL SUBJECT TO CARBAMAZEPINE (CBZ) TREATMENT WAS ESTABLISHED, AND TRANSCRIPTOME- AND GENOME-SCALE PROFILING OF H3K9AC AND HDAC3 WAS PERFORMED BY RNA-SEQ AND CHIP-SEQ. WE OBSERVED THAT H3K9AC LEVELS IN THE TRIGEMINAL GANGLION WERE LOWER IN THE TN RATS COMPARED WITH THOSE IN THE CONTROL, AND CBZ TREATMENT LED TO RECOVERY OF H3K9AC LEVELS. FURTHER, WE FOUND THAT HDAC3 WAS OVERACTIVATED, WHICH INTERFERED WITH H3K9 ACETYLATION DUE TO HIGHER PHOSPHORYLATION IN TN COMPARED WITH THAT IN THE CONTROL. FINALLY, THE PHOSPHOKINASE LEUCINE-RICH REPEAT KINASE 2 (LRRK2) WAS DEMONSTRATED TO CONTRIBUTE TO HDAC3 ACTIVITY VIA THE MAPK SIGNALING PATHWAY. TAKEN TOGETHER, WE IDENTIFIED A REGULATORY MECHANISM IN WHICH THE PHOSPHATE GROUPS TRANSFERRED FROM ACTIVATED ERK AND LRRK2 TO HDAC3 CAUSED GENOME-SCALE DEACETYLATION AT H3K9 AND RESULTED IN THE SILENCING OF A LARGE NUMBER OF GENES IN TN. THE KINASES OR IMPORTANT ENZYMES WITHIN THIS REGULATORY AXIS MAY REPRESENT IMPORTANT TARGETS FOR TN THERAPY AND PREVENTION. 2022 3 6148 36 THE EXPRESSION OF TRANSCRIPTION FACTORS MECP2 AND CREB IS MODULATED IN INFLAMMATORY PELVIC PAIN. EARLY ACTIVATION OF TRANSCRIPTION FACTORS IS ONE OF THE EPIGENETIC MECHANISMS CONTRIBUTING TO THE INDUCTION AND MAINTENANCE OF CHRONIC PAIN STATES. PREVIOUS STUDIES IDENTIFIED THE CHANGES IN A NUMBER OF NOCICEPTION-RELATED GENES, SUCH AS CALCITONIN GENE-RELATED PEPTIDE (CGRP), SUBSTANCE P (SP), AND BRAIN-DERIVED NEUROTROPIC FACTOR (BDNF) IN THE PELVIC ORGANS AFTER TRANSIENT COLONIC INFLAMMATION. THE GENE AND PROTEIN EXPRESSION OF THESE NEUROPEPTIDES COULD BE MODULATED BY TRANSCRIPTION FACTORS METHYL-CPG-BINDING PROTEIN 2 (MECP2) AND CAMP RESPONSE ELEMENT-BINDING PROTEIN (CREB). IN THIS STUDY, WE AIMED TO EVALUATE TIME-DEPENDENT CHANGES IN THE EXPRESSION LEVELS OF MECP2 AND CREB IN THE LUMBOSACRAL (LS) SPINAL CORD AND SENSORY GANGLIA AFTER INFLAMMATION-INDUCED PELVIC PAIN IN RAT. ADULT SPRAGUE-DAWLEY RATS WERE TREATED WITH 2,4,6-TRINITROBENZENESULFONIC ACID (TNBS) TO INDUCE TRANSIENT COLONIC INFLAMMATION. LS (L6-S2) SPINAL CORD SEGMENTS AND RESPECTIVE DORSAL ROOT GANGLIAS (DRGS) WERE ISOLATED FROM CONTROL AND EXPERIMENTAL ANIMALS AT 1, 2, 6, 24 H AND 3 DAYS POST-TNBS TREATMENT. IMMUNOHISTOCHEMICAL (IHC) LABELING AND WESTERN BLOTTING EXPERIMENTS WERE PERFORMED TO ASSESS THE EXPRESSION OF MECP2, CREB AND THEIR PHOSPHORYLATED FORMS. TOTAL MECP2 EXPRESSION, BUT NOT PHOSPHORYLATED P-MECP2 (PS421MECP2) EXPRESSION WAS DETECTED IN THE CELLS OF THE SPINAL DORSAL HORN UNDER CONTROL CONDITIONS. COLONIC INFLAMMATION TRIGGERED A SIGNIFICANT DECREASE IN THE NUMBER OF MECP2-EXPRESSING NEURONS IN PARALLEL WITH ELEVATED NUMBERS OF PS421MECP2-EXPRESSING CELLS AT 2 H AND 6 H POST-TNBS. THE MAJORITY OF MECP2-POSITIVE CELLS (80 +/- 6%) CO-EXPRESSED CREB. TNBS TREATMENT CAUSED A TRANSIENT UP-REGULATION OF CREB-EXPRESSING CELLS AT 1 H POST-TNBS ONLY. THE NUMBER OF CELLS EXPRESSING PHOSPHORYLATED CREB (PS133CREB) DID NOT CHANGE AT 1 H AND 2 H POST-TNBS, BUT WAS DOWN-REGULATED BY THREE FOLDS AT 6 H POST-TNBS. ANALYSIS OF DRG SECTIONS REVEALED THAT THE NUMBER OF MECP2-POSITIVE NEURONS WAS UP-REGULATED BY TNBS TREATMENT, REACHING THREE-FOLD INCREASE AT 2 H POST-TNBS, AND EIGHT-FOLD INCREASE AT 6 H POST-TNBS (P