Development of Inflammatory Hypoxia and Prevalence of Glycolytic Metabolism in Progressing Herpes Stromal Keratitis Lesions

Abstract

Chronic inflammation in tissues often causes the development of hypoxia. Herpes stromal keratitis (HSK) is a corneal chronic inflammatory condition that develops in response to recurrent HSV-1 infection. In this study, we investigated the development of hypoxia, the expression of hypoxia-associated glycolytic genes in HSV-1 infected corneas, and the outcome of blocking hypoxiainducible factor (HIF) dimerization on the severity of HSK. Our results showed the development of hypoxia, an elevated expression of hypoxia-associated glycolytic genes, and an increased level of lactate in corneas with progressing HSK lesions. The magnitude of hypoxia correlated with the extent of neutrophils infiltrating the infected corneas, and the depletion of neutrophils reduced the development of hypoxia in infected corneas. Additionally, in progressing HSK lesions, nuclear localization of HIF-2a protein was detected in corneal epithelial cells, whereas HIF-1a protein stabilization was observed in infiltrating immune cells. Administration of acriflavine drug to HSV-1-infected mice inhibited nuclear accumulation of HIF-1a and HIF-2a protein in immune cell types and epithelial cells, respectively, in infected corneas. As a result, a decreased influx of CD4 T cells and nongranulocytic myeloid cells, but an increased influx of neutrophils, was noted in developing HSK lesions. Interestingly, acriflavine treatment given during the clinical disease period decreased neovascularization but increased the opacity in HSV-1-infected corneas. Taken together, the results of our study lay the foundation to dissect the role of inflammatory hypoxia and hypoxia-associated genes in the pathogenesis of HSK.

Implications of cellular metabolism for immune cell migration

“…65 Another setting where neutrophil infiltration creates a hypoxic microenvironment is during the development of herpes stromal keratitis, a chronic inflammatory condition of the cornea due to recurrent herpes simplex virus-1 infection. 66 However, in this case, hypoxia partly contributes to the progression of these lesions, with HIF-2ɑ becoming stabilized in the epithelial cells of these lesions, while HIF-1ɑ is stabilized in the infiltrating immune cells. Microenvironmental O 2 depletion during disease settings that involve heavy neutrophil infiltration is not always as a result of neutrophil respiratory burst, however.…”

Role of Insulin-Like Growth Factor Binding Protein-3 in the Pathogenesis of Herpes Stromal Keratitis

“…Several factors such as TGF-β1, IGF-I, retinoic acid, TNF-α, and hypoxia are known to upregulate IGFBP-3 mRNA expression. [40][41][42] We recently showed the development of hypoxia in HSK-developing corneas, 43 suggesting a possibility that hypoxia might upregulate the expression of IGFBP-3 in HSK lesions. Once expressed, IGFBP-3 protein is secreted out of the cell but can be taken up in an autocrine or paracrine action through a variety of endocytic mechanisms involving caveolin-1 and clathrin-coated pits.…”

Pathogenesis of Herpes Stromal Keratitis: Immune Inflammatory Response Mediated by Inflammatory Regulators

“…Large numbers of neutrophils and CD4 + T cells are detected in the HSV-1infected corneal stroma. In the preclinical stage of HSK, increased expression of hypoxia-related glycolytic genes are detected in the corneas of HSV-1-infected mice, and viral replication in the infected cornea is triggered by innate immune responses during the early stage of infection, which induce neutrophil aggregation (143). Some studies have reported a correlation between hypoxia and inflammation.…”

“…Moreover, tissue hypoxia can induce corneal angiogenesis, which aggravates visual impairment. Hypoxia inducible factors (HIFs) are present in the infected cornea, and blocking HIF-1α and HIF-2α expression with acriflavine can reduce the severity of HSK and induce regression of CNV (143). In summary, hypoxia plays an important role in HSK pathogenesis.…”