lucifer-yellow and Inflammation

Peripheral sensory ganglia contain the somata of neurons mediating mechanical, thermal, and painful sensations from somatic, visceral, and oro-facial organs. Each neuronal cell body is closely surrounded by satellite glial cells (SGCs) that have properties and functions similar to those of central astrocytes, including expression of gap junction proteins and functional dye coupling. As shown in other pain models, after systemic pain induction by intra-peritoneal injection of lipopolysaccharide, dye coupling among SGCs in intact trigeminal ganglion was enhanced. Moreover, neuron-neuron and neuron-SGC coupling was also detected. To verify the presence of gap junction-mediated coupling between SGCs and sensory neurons, we performed dual whole cell patch clamp recordings from both freshly isolated and short term cultured cell pairs dissociated from mouse trigeminal ganglia. Bidirectional gap junction mediated electrical responses were frequently recorded between SGCs, between neurons and between neurons and SGCs. Polarization of SGC altered neuronal excitability, providing evidence that gap junction-mediated interactions between neurons and glia within sensory ganglia may contribute to integration of peripheral sensory responses, and to the modulation and coordinaton of neuronal activity.

Topics: Animals; Boron Compounds; Carbenoxolone; Cells, Cultured; Disease Models, Animal; Female; Flufenamic Acid; Gap Junctions; Heptanol; Inflammation; Isoquinolines; Lipopolysaccharides; Male; Membrane Potentials; Mice; Mice, Inbred C57BL; Neuroglia; Neurons; Probenecid; Synaptic Transmission; Trigeminal Ganglion

In this study, we investigated how tannic acid (TA) protects the skin from inflammation caused by external irritation. The effects of TA were evaluated using a mouse 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced skin inflammation model and a reconstructed human epidermal model. We then used Lucifer Yellow for visual confirmation of TA's suppression effect at the stratum corneum (SC) surface. TA treatment of the skin prevented Lucifer Yellow from permeating the skin. This result suggests that TA acts as a barrier against external stimulants such as TPA and artificial sweat on the SC surface.

Topics: Animals; Dermatitis, Contact; Disease Models, Animal; Epidermis; Fluorescent Dyes; Inflammation; Isoquinolines; Male; Mice; Mice, Inbred ICR; Permeability; Skin; Skin Diseases; Sweat; Tannins; Tetradecanoylphorbol Acetate

In this work, the effects of bacterial LPS, TNF-alpha, and IFN-gamma on gap junctional communication (dye coupling) and on the expression of connexin43 (immunofluorescence, immunoblotting, and RT-PCR) in monocytes/macrophages were studied. Freshly isolated human monocytes plated at high density and treated either with LPS plus IFN-gamma or TNF-alpha plus IFN-gamma became transiently dye coupled (Lucifer yellow) within 24 h. Cells treated with LPS, TNF-alpha, or IFN-gamma alone remained dye uncoupled. In dye-coupled cells, the spread of Lucifer yellow to neighboring cells was reversibly blocked with 18 alpha-glycyrrhetinic acid, a gap junction blocker, but it was unaffected by oxidized ATP or probenecid, which block ionotropic ATP-activated channels and organic anion transporters, respectively. Abs against TNF-alpha significantly reduced the LPS plus IFN-gamma-induced increase in dye coupling. In dye-coupled monocytes/macrophages, but not in control cells, both connexin43 protein and mRNA were detected, and their levels were higher in cells with an elevated incidence of dye coupling. In dye-coupled cells, the localization of connexin43 immunoreactivity was diffuse at perinuclear regions and thin cell processes. The addition of 18-alpha-glycyrrhetinic acid induced a profound reduction of monocyte/macrophage transmigration across a blood brain barrier model. It also induced a significant reduction in the secretion of metalloproteinase-2 in cells treated with TNF-alpha plus IFN-gamma. We propose that some monocyte/macrophage responses are coordinated by connexin-formed membrane channels expressed transiently at inflammatory sites in which these cells form aggregates.

Topics: Adjuvants, Immunologic; Blood-Brain Barrier; Cell Communication; Cell Movement; Cells, Cultured; Connexin 43; Drug Synergism; Gap Junctions; Humans; Inflammation; Interferon-gamma; Isoquinolines; Lipopolysaccharides; Macrophages; Matrix Metalloproteinase 2; Matrix Metalloproteinase 9; Monocytes; RNA, Messenger; Tumor Necrosis Factor-alpha

We previously reported that gabapentin (GBP), a widely prescribed analgesic, enhances N-methyl-aspartate (NMDA) receptor mediated currents only when the intracellular level of protein kinase C is elevated. However, it is unclear how the potentiation of NMDA responses by GBP can lead to pain relief. To resolve this issue, we combined immunocytochemical and patch recording techniques to study the actions of GBP on NMDA receptors in dorsal horn cells isolated from rats with inflammation and to determine the gamma-aminobutyric acid (GABA) content in the recorded cells. We found that all GBP-responsive cells are GABA-immunoreactive and none of the GABA-negative neurons respond to GBP. Thus, GBP appears to enhance NMDA currents in GABAergic neurons. These observations suggest that GBP exerts its antinociceptive action by increasing the activity of these inhibitory neurons.

Topics: Acetates; Afferent Pathways; Amines; Analgesics; Animals; Cyclohexanecarboxylic Acids; Fluorescent Dyes; Gabapentin; gamma-Aminobutyric Acid; Immunohistochemistry; Inflammation; Ion Channels; Isoquinolines; Lysine; Membrane Potentials; Nociceptors; Pain; Patch-Clamp Techniques; Posterior Horn Cells; Protein Kinase C; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Synaptic Transmission

The effect of peripheral inflammation on spontaneous firing and level of substance P (SP) and its receptor in electrophysiologically identified cat Abeta neurons of dorsal root ganglion (DRG) was studied in vivo using a combination of intracellular recording, dye injection and immunohistochemical techniques. Following injection of carrageenan (Carg) into cat hindpaw, the number of Abeta neurons with spontaneous firing was enhanced significantly (42.9%, n=182) in comparison with control (16.8%, n=149, P<0.01). DRG Abeta neurons became less depolarized 2-4 h following Carg injection. After identifying the cell properties, Lucifer Yellow was injected and SP-like immunoreactivity (SP-LI) was then detected. A total of 17% of Abeta sensory neurons exhibited SP-LI in inflammatory cat. We also found in rat DRGs that the number of SP-LI positive large cells (>35 microm) was also significantly increased in Carg-treated DRG (11.8+/-1.2, n=8) compared with untreated DRG (1.8+/-0.8, n=8, P<0.01). In control cat, the topical use of SP in DRG did not induce any response of Abeta neurons. However, in Carg-treated cat, SP depolarized the membrane potential in most Abeta neurons (68.2%, n=22). L668,169, an antagonist of SP receptor, completely blocked the SP-induced responses. Furthermore, repeated application of SP did not induce obvious desensitization of Abeta neurons. These data suggest that peripheral inflammation increased the excitability, SP level and sensitivity of SP receptor of Abeta neurons. Therefore, we concluded that Abeta sensory neurons appear to contribute to inflammatory allodynia.

Topics: Action Potentials; Administration, Topical; Animals; Carrageenan; Cats; Electrophysiology; Fluorescent Dyes; Ganglia, Spinal; Immunohistochemistry; Inflammation; Isoquinolines; Male; Neurons, Afferent; Phenotype; Rats; Rats, Sprague-Dawley; Receptors, Neurokinin-1; Substance P