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Minocycline attenuates microglial activation but fails to mitigate striatal dopaminergic neurotoxicity: role of tumor necrosis factor-alpha.
J Neurochem. 2006 Feb; 96(3):706-18.JN

Abstract

Activated microglia are implicated in the pathogenesis of disease-, trauma- and toxicant-induced damage to the CNS, and strategies to modulate microglial activation are gaining impetus. A novel action of the tetracycline derivative minocycline is the ability to inhibit inflammation and free radical formation, factors that influence microglial activation. Minocycline is therefore being tested as a neuroprotective agent to alleviate CNS damage, although findings so far have yielded mixed results. Here, we showed that administration of a single low dose of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) or methamphetamine (METH), a paradigm that causes selective degeneration of striatal dopaminergic nerve terminals without affecting the cell body in substantia nigra, increased the expression of mRNAs encoding microglia-associated factors F4/80, interleukin (IL)-1alpha, IL-6, monocyte chemoattractant protein-1 (MCP-1, CCL2) and tumor necrosis factor (TNF)-alpha. Minocycline treatment attenuated MPTP- or METH-mediated microglial activation, but failed to afford neuroprotection. Lack of neuroprotection was shown to be due to the inability of minocycline to abolish the induction of TNF-alpha and its receptors, thereby failing to modulate TNF signaling. Thus, TNF-alpha appeared to be an obligatory component of dopaminergic neurotoxicity. To address this possibility, we examined the effects of MPTP or METH in mice lacking genes encoding IL-6, CCL2 or TNF receptor (TNFR)1/2. Deficiency of either IL-6 or CCL2 did not alter MPTP neurotoxicity. However, deficiency of both TNFRs protected against the dopaminergic neurotoxicity of MPTP. Taken together, our findings suggest that attenuation of microglial activation is insufficient to modulate neurotoxicity as transient activation of microglia may suffice to initiate neurodegeneration. These findings support the hypothesis that TNF-alpha may play a role in the selective vulnerability of the nigrostriatal pathway associated with dopaminergic neurotoxicity and perhaps Parkinson's disease.

Authors+Show Affiliations

Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Morgantown, WV 26505, USA.No affiliation info availableNo affiliation info available

Pub Type(s)

Comparative Study
Journal Article

Language

eng

PubMed ID

16405514

Citation

Sriram, Krishnan, et al. "Minocycline Attenuates Microglial Activation but Fails to Mitigate Striatal Dopaminergic Neurotoxicity: Role of Tumor Necrosis Factor-alpha." Journal of Neurochemistry, vol. 96, no. 3, 2006, pp. 706-18.
Sriram K, Miller DB, O'Callaghan JP. Minocycline attenuates microglial activation but fails to mitigate striatal dopaminergic neurotoxicity: role of tumor necrosis factor-alpha. J Neurochem. 2006;96(3):706-18.
Sriram, K., Miller, D. B., & O'Callaghan, J. P. (2006). Minocycline attenuates microglial activation but fails to mitigate striatal dopaminergic neurotoxicity: role of tumor necrosis factor-alpha. Journal of Neurochemistry, 96(3), 706-18.
Sriram K, Miller DB, O'Callaghan JP. Minocycline Attenuates Microglial Activation but Fails to Mitigate Striatal Dopaminergic Neurotoxicity: Role of Tumor Necrosis Factor-alpha. J Neurochem. 2006;96(3):706-18. PubMed PMID: 16405514.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Minocycline attenuates microglial activation but fails to mitigate striatal dopaminergic neurotoxicity: role of tumor necrosis factor-alpha. AU - Sriram,Krishnan, AU - Miller,Diane B, AU - O'Callaghan,James P, Y1 - 2006/01/09/ PY - 2006/1/13/pubmed PY - 2006/3/31/medline PY - 2006/1/13/entrez SP - 706 EP - 18 JF - Journal of neurochemistry JO - J Neurochem VL - 96 IS - 3 N2 - Activated microglia are implicated in the pathogenesis of disease-, trauma- and toxicant-induced damage to the CNS, and strategies to modulate microglial activation are gaining impetus. A novel action of the tetracycline derivative minocycline is the ability to inhibit inflammation and free radical formation, factors that influence microglial activation. Minocycline is therefore being tested as a neuroprotective agent to alleviate CNS damage, although findings so far have yielded mixed results. Here, we showed that administration of a single low dose of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) or methamphetamine (METH), a paradigm that causes selective degeneration of striatal dopaminergic nerve terminals without affecting the cell body in substantia nigra, increased the expression of mRNAs encoding microglia-associated factors F4/80, interleukin (IL)-1alpha, IL-6, monocyte chemoattractant protein-1 (MCP-1, CCL2) and tumor necrosis factor (TNF)-alpha. Minocycline treatment attenuated MPTP- or METH-mediated microglial activation, but failed to afford neuroprotection. Lack of neuroprotection was shown to be due to the inability of minocycline to abolish the induction of TNF-alpha and its receptors, thereby failing to modulate TNF signaling. Thus, TNF-alpha appeared to be an obligatory component of dopaminergic neurotoxicity. To address this possibility, we examined the effects of MPTP or METH in mice lacking genes encoding IL-6, CCL2 or TNF receptor (TNFR)1/2. Deficiency of either IL-6 or CCL2 did not alter MPTP neurotoxicity. However, deficiency of both TNFRs protected against the dopaminergic neurotoxicity of MPTP. Taken together, our findings suggest that attenuation of microglial activation is insufficient to modulate neurotoxicity as transient activation of microglia may suffice to initiate neurodegeneration. These findings support the hypothesis that TNF-alpha may play a role in the selective vulnerability of the nigrostriatal pathway associated with dopaminergic neurotoxicity and perhaps Parkinson's disease. SN - 0022-3042 UR - https://www.unboundmedicine.com/medline/citation/16405514/Minocycline_attenuates_microglial_activation_but_fails_to_mitigate_striatal_dopaminergic_neurotoxicity:_role_of_tumor_necrosis_factor_alpha_ L2 - https://doi.org/10.1111/j.1471-4159.2005.03566.x DB - PRIME DP - Unbound Medicine ER -