Hyposmotic stimulation-induced nitric oxide production in outer hair cells of the guinea pig cochlea

• Published in: Hearing research Vol. 230; no. 1; pp. 93 - 104
• Main Authors: Takeda-Nakazawa, Hiroko, Harada, Narinobu, Shen, Jing, Kubo, Nobuo, Zenner, Hans-Peter, Yamashita, Toshio
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.08.2007
• Subjects: 8-Bromo Cyclic Adenosine Monophosphate - pharmacology; Animals; Calcium - metabolism; Carbazoles - pharmacology; Cell Size - drug effects; Cells, Cultured; Cochlea; Cyclic GMP - metabolism; Cyclic GMP-Dependent Protein Kinases - antagonists & inhibitors; Cyclic GMP-Dependent Protein Kinases - metabolism; DAF-2 DA; Enzyme Inhibitors - pharmacology; Gadolinium - pharmacology; Guanylate Cyclase - antagonists & inhibitors; Guanylate Cyclase - metabolism; Guinea Pigs; Hair Cells, Auditory, Outer - drug effects; Hair Cells, Auditory, Outer - metabolism; Hypotonic Solutions; Hypotonic stimulation; Indoles - pharmacology; Kinetics; Membrane Potentials; NG-Nitroarginine Methyl Ester - pharmacology; Nitric oxide; Nitric Oxide - metabolism; Nitric Oxide Donors - pharmacology; Nitric Oxide Synthase - antagonists & inhibitors; Nitric Oxide Synthase - metabolism; Organ of Corti - cytology; Organ of Corti - drug effects; Organ of Corti - metabolism; Osmotic Pressure; Outer hair cell; Phorbol Esters - pharmacology; Potassium - metabolism; Purinergic P2 Receptor Antagonists; Receptors, Purinergic P2 - metabolism; S-Nitroso-N-Acetylpenicillamine - pharmacology; Signal Transduction - drug effects; Sodium Chloride - metabolism; Suramin - pharmacology; Transient receptor potential vanilloid 4; TRPV Cation Channels - agonists; TRPV Cation Channels - metabolism; NO; [K +] i; eNOS; DMSO; DAF-2 DA; DAF-2DA; OHCs; Transient receptor potential vanilloid 4; IHCs; Outer hair cell; 4α-PDD; [Ca 2+] i, intracellular Ca 2+ concentrations; nitric oxide synthase; Hypotonic stimulation; ODQ; ROIs; l-NAME; SNAP; PKG; EGTA; PSS; TRPV4; Nitric oxide; nNOS; Cochlea
• ISSN: 0378-5955; 1878-5891
• DOI: 10.1016/j.heares.2007.05.010

Nitric oxide (NO) production during hyposmotic stimulation in outer hair cells (OHCs) of the guinea pig cochlea was investigated using the NO sensitive dye DAF-2. Simultaneous measurement of the cell length and NO production showed rapid hyposmotic-induced cell swelling to precede NO production in OHCs. Hyposmotic stimulation failed to induce NO production in the Ca 2+-free solution. l- N G-nitroarginine methyl ester ( l-NAME), a non-specific NO synthase inhibitor and gadolinium, a stretch-activated channel blocker inhibited the hyposmotic stimulation-induced NO production whereas suramin, a P2 receptor antagonist did not. S-nitroso- N-acetylpenicillamine (SNAP), a NO donor inhibited the hyposmotic stimulation-induced increase in the intracellular Ca 2+ concentrations ([Ca 2+] i) while l-NAME enhanced it. 1 H-[1,2,4]oxadiazole[4,3 a]quinoxalin-1-one, an inhibitor of guanylate cyclase and KT5823, an inhibitor of cGMP-dependent protein kinase (PKG) mimicked effects of l-NAME on the Ca 2+ response. Transient receptor potential vanilloid 4 (TRPV4), an osmo- and mechanosensitive channel was expressed in the OHCs by means of immunohistochemistry. 4α-phorbol 12,13-didecanoate, a TRPV4 synthetic activator, induced NO production in OHCs. These results suggest that hyposmotic stimulation can induce NO production by the [Ca 2+] i increase, which is presumably mediated by the activation of TRPV4 in OHCs. NO conversely inhibits the Ca 2+ response via the NO-cGMP-PKG pathway by a feedback mechanism.