Replication of Mycobacterium tuberculosis in retinal pigment epithelium

Hossein Nazari, Petros Karakousis, Narsing A. Rao

Research output: Contribution to journalArticle

Abstract

IMPORTANCE: Mycobacterium tuberculosis is an important cause of posterior uveitis in tuberculosis-endemic regions. Clinical and histopathologic evidence suggests that retinal pigment epithelium (RPE) can harbor M tuberculosis. However, the mechanism of M tuberculosis phagocytosis and its growth in RPE is not clear. OBJECTIVE To investigate M tuberculosis phagocytosis, replication, and cytopathic effects in RPE cells compared with macrophages. DESIGN, SETTING, AND PARTICIPANTS: Human fetal RPE and monocytic leukemia macrophage (THP-1) cell lines were cultured, and RPE and THP-1 cells were exposed to avirulent M tuberculosis H37Ra. Mycobacteria were added to RPE and THP-1 cells with a 5:1 multiplicity of infection. Nonphagocytized M tuberculosis was removed after 12 hours of exposure (day 0). Cells were harvested at days 0, 1, and 5 to count live and dead cells and intracellular mycobacteria. Toll-like receptor 2 (TLR2) and TLR4 expression was determined by immunohistochemistry; intracellular bacillary load, following TLR2 and TLR4 blockade. MAIN OUTCOMES AND MEASURES: Number of intracellular M tuberculosis, cell survival, and TLR2 and TLR4 expression in RPE and THP-1 cells following exposure to M tuberculosis. RESULTS: At day 0, an equal number of intracellular M tuberculosis was observed per THP-1 and RPE cells (0.45 and 0.35 M tuberculosis per RPE and THP-1 cells, respectively). Mean (SD) number of intracellular M tuberculosis at day 5 was 1.9 (0.03) and 3.3 (0.01) per RPE and THP-1 cells, respectively (P <.001). Viability of infected RPE was significantly greater than that of THP-1 cells at day 5 (viable cells: 17 [8%] THP-1 vs 73%[4%] RPE; P <.05). Expression of TLR2 and TLR4 was detected in both cell types after 12 hours of exposure. Inhibition of TLR2 and TLR4 reduced intracellular M tuberculosis counts in RPE but not in THP-1 cells. CONCLUSIONS AND RELEVANCE: Mycobacterium tuberculosis is phagocytized by RPE to a similar extent as in macrophages. However, RPE cells are better able to control bacillary growth and RPE cell survival is greater than that of THP-1 cells followingmycobacterial infection, suggesting that RPE can serve as a reservoir for intraocular M tuberculosis infection.

Original languageEnglish (US)
Pages (from-to)724-729
Number of pages6
JournalJAMA Ophthalmology
Volume132
Issue number6
DOIs
StatePublished - 2014

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Retinal Pigment Epithelium
Mycobacterium tuberculosis
Tuberculosis
Toll-Like Receptor 2
Macrophages
Mycobacterium
Phagocytosis
Cell Survival
Infection
Posterior Uveitis
Growth

ASJC Scopus subject areas

  • Ophthalmology

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Replication of Mycobacterium tuberculosis in retinal pigment epithelium. / Nazari, Hossein; Karakousis, Petros; Rao, Narsing A.

In: JAMA Ophthalmology, Vol. 132, No. 6, 2014, p. 724-729.

Research output: Contribution to journalArticle

Nazari, Hossein ; Karakousis, Petros ; Rao, Narsing A. / Replication of Mycobacterium tuberculosis in retinal pigment epithelium. In: JAMA Ophthalmology. 2014 ; Vol. 132, No. 6. pp. 724-729.
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abstract = "IMPORTANCE: Mycobacterium tuberculosis is an important cause of posterior uveitis in tuberculosis-endemic regions. Clinical and histopathologic evidence suggests that retinal pigment epithelium (RPE) can harbor M tuberculosis. However, the mechanism of M tuberculosis phagocytosis and its growth in RPE is not clear. OBJECTIVE To investigate M tuberculosis phagocytosis, replication, and cytopathic effects in RPE cells compared with macrophages. DESIGN, SETTING, AND PARTICIPANTS: Human fetal RPE and monocytic leukemia macrophage (THP-1) cell lines were cultured, and RPE and THP-1 cells were exposed to avirulent M tuberculosis H37Ra. Mycobacteria were added to RPE and THP-1 cells with a 5:1 multiplicity of infection. Nonphagocytized M tuberculosis was removed after 12 hours of exposure (day 0). Cells were harvested at days 0, 1, and 5 to count live and dead cells and intracellular mycobacteria. Toll-like receptor 2 (TLR2) and TLR4 expression was determined by immunohistochemistry; intracellular bacillary load, following TLR2 and TLR4 blockade. MAIN OUTCOMES AND MEASURES: Number of intracellular M tuberculosis, cell survival, and TLR2 and TLR4 expression in RPE and THP-1 cells following exposure to M tuberculosis. RESULTS: At day 0, an equal number of intracellular M tuberculosis was observed per THP-1 and RPE cells (0.45 and 0.35 M tuberculosis per RPE and THP-1 cells, respectively). Mean (SD) number of intracellular M tuberculosis at day 5 was 1.9 (0.03) and 3.3 (0.01) per RPE and THP-1 cells, respectively (P <.001). Viability of infected RPE was significantly greater than that of THP-1 cells at day 5 (viable cells: 17 [8{\%}] THP-1 vs 73{\%}[4{\%}] RPE; P <.05). Expression of TLR2 and TLR4 was detected in both cell types after 12 hours of exposure. Inhibition of TLR2 and TLR4 reduced intracellular M tuberculosis counts in RPE but not in THP-1 cells. CONCLUSIONS AND RELEVANCE: Mycobacterium tuberculosis is phagocytized by RPE to a similar extent as in macrophages. However, RPE cells are better able to control bacillary growth and RPE cell survival is greater than that of THP-1 cells followingmycobacterial infection, suggesting that RPE can serve as a reservoir for intraocular M tuberculosis infection.",
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N2 - IMPORTANCE: Mycobacterium tuberculosis is an important cause of posterior uveitis in tuberculosis-endemic regions. Clinical and histopathologic evidence suggests that retinal pigment epithelium (RPE) can harbor M tuberculosis. However, the mechanism of M tuberculosis phagocytosis and its growth in RPE is not clear. OBJECTIVE To investigate M tuberculosis phagocytosis, replication, and cytopathic effects in RPE cells compared with macrophages. DESIGN, SETTING, AND PARTICIPANTS: Human fetal RPE and monocytic leukemia macrophage (THP-1) cell lines were cultured, and RPE and THP-1 cells were exposed to avirulent M tuberculosis H37Ra. Mycobacteria were added to RPE and THP-1 cells with a 5:1 multiplicity of infection. Nonphagocytized M tuberculosis was removed after 12 hours of exposure (day 0). Cells were harvested at days 0, 1, and 5 to count live and dead cells and intracellular mycobacteria. Toll-like receptor 2 (TLR2) and TLR4 expression was determined by immunohistochemistry; intracellular bacillary load, following TLR2 and TLR4 blockade. MAIN OUTCOMES AND MEASURES: Number of intracellular M tuberculosis, cell survival, and TLR2 and TLR4 expression in RPE and THP-1 cells following exposure to M tuberculosis. RESULTS: At day 0, an equal number of intracellular M tuberculosis was observed per THP-1 and RPE cells (0.45 and 0.35 M tuberculosis per RPE and THP-1 cells, respectively). Mean (SD) number of intracellular M tuberculosis at day 5 was 1.9 (0.03) and 3.3 (0.01) per RPE and THP-1 cells, respectively (P <.001). Viability of infected RPE was significantly greater than that of THP-1 cells at day 5 (viable cells: 17 [8%] THP-1 vs 73%[4%] RPE; P <.05). Expression of TLR2 and TLR4 was detected in both cell types after 12 hours of exposure. Inhibition of TLR2 and TLR4 reduced intracellular M tuberculosis counts in RPE but not in THP-1 cells. CONCLUSIONS AND RELEVANCE: Mycobacterium tuberculosis is phagocytized by RPE to a similar extent as in macrophages. However, RPE cells are better able to control bacillary growth and RPE cell survival is greater than that of THP-1 cells followingmycobacterial infection, suggesting that RPE can serve as a reservoir for intraocular M tuberculosis infection.

AB - IMPORTANCE: Mycobacterium tuberculosis is an important cause of posterior uveitis in tuberculosis-endemic regions. Clinical and histopathologic evidence suggests that retinal pigment epithelium (RPE) can harbor M tuberculosis. However, the mechanism of M tuberculosis phagocytosis and its growth in RPE is not clear. OBJECTIVE To investigate M tuberculosis phagocytosis, replication, and cytopathic effects in RPE cells compared with macrophages. DESIGN, SETTING, AND PARTICIPANTS: Human fetal RPE and monocytic leukemia macrophage (THP-1) cell lines were cultured, and RPE and THP-1 cells were exposed to avirulent M tuberculosis H37Ra. Mycobacteria were added to RPE and THP-1 cells with a 5:1 multiplicity of infection. Nonphagocytized M tuberculosis was removed after 12 hours of exposure (day 0). Cells were harvested at days 0, 1, and 5 to count live and dead cells and intracellular mycobacteria. Toll-like receptor 2 (TLR2) and TLR4 expression was determined by immunohistochemistry; intracellular bacillary load, following TLR2 and TLR4 blockade. MAIN OUTCOMES AND MEASURES: Number of intracellular M tuberculosis, cell survival, and TLR2 and TLR4 expression in RPE and THP-1 cells following exposure to M tuberculosis. RESULTS: At day 0, an equal number of intracellular M tuberculosis was observed per THP-1 and RPE cells (0.45 and 0.35 M tuberculosis per RPE and THP-1 cells, respectively). Mean (SD) number of intracellular M tuberculosis at day 5 was 1.9 (0.03) and 3.3 (0.01) per RPE and THP-1 cells, respectively (P <.001). Viability of infected RPE was significantly greater than that of THP-1 cells at day 5 (viable cells: 17 [8%] THP-1 vs 73%[4%] RPE; P <.05). Expression of TLR2 and TLR4 was detected in both cell types after 12 hours of exposure. Inhibition of TLR2 and TLR4 reduced intracellular M tuberculosis counts in RPE but not in THP-1 cells. CONCLUSIONS AND RELEVANCE: Mycobacterium tuberculosis is phagocytized by RPE to a similar extent as in macrophages. However, RPE cells are better able to control bacillary growth and RPE cell survival is greater than that of THP-1 cells followingmycobacterial infection, suggesting that RPE can serve as a reservoir for intraocular M tuberculosis infection.

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