The epitranscriptomic writer ALKBH8 drives tolerance and protects mouse lungs from the environmental pollutant naphthalene

Abstract

The epitranscriptomic writer Alkylation Repair Homolog 8 (ALKBH8) is a transfer RNA (tRNA) methyltransferase that modifies the wobble uridine of selenocysteine tRNA to promote the specialized translation of selenoproteins. Using Alkbh8 deficient (Alkbh8^def) mice, we have investigated the importance of epitranscriptomic systems in the response to naphthalene, an abundant polycyclic aromatic hydrocarbon and environmental toxicant. We performed basal lung analysis and naphthalene exposure studies using wild type (WT), Alkbh8^def and Cyp2abfgs-null mice, the latter of which lack the cytochrome P450 enzymes required for naphthalene bioactivation. Under basal conditions, lungs from Alkbh8^def mice have increased markers of oxidative stress and decreased thioredoxin reductase protein levels, and have reprogrammed gene expression to differentially regulate stress response transcripts. Alkbh8^def mice are more sensitive to naphthalene induced death than WT, showing higher susceptibility to lung damage at the cellular and molecular levels. Further, WT mice develop a tolerance to naphthalene after 3 days, defined as resistance to a high challenging dose after repeated exposures, which is absent in Alkbh8^def mice. We conclude that the epitranscriptomic writer ALKBH8 plays a protective role against naphthalene-induced lung dysfunction and promotes naphthalene tolerance. Our work provides an early example of how epitranscriptomic systems can regulate the response to environmental stress in vivo.

Keywords: ALKBH8; Epitranscriptomics; RNA modification; naphthalene; selenoprotein; stress response; tolerance; translation.

Figure 1.

ALKBH8 domain structure, modification chemistry and the translation of selenoproteins.

Figure 2.

Alkbh8^def lungs have decreased levels of specific selenoproteins and transcriptionally reprogram stress response systems.

Figure 3.

Markers of oxidative stress and increased DNA damage response observed in Alkbh8^def lungs.

Figure 4.

Alkbh8^def mice and lungs are more sensitive to damage from naphthalene.

Figure 5.

Altered stress response to naphthalene observed in Alkbh8^def lungs.

Figure 6.

Alkbh8 deficient mice show increased mortality and fail to develop tolerance to naphthalene exposure.

Figure 7.

Model for the epitranscriptomic writer based response to naphthalene. Our study supports a model in which ALKBH8-catalysed epitranscriptomic marks promote the translation of selenoproteins important for handling stress, preventing naphthalene toxicity and driving tolerance.