Nano-titanium dioxide inhalation exposure during gestation drives redox dysregulation and vascular dysfunction across generations

Abstract

Background Pregnancy is associated with many rapid biological adaptations that support healthy development of the growing fetus. One of which is critical to fetal health and development is the coordination between maternal liver derived substrates and vascular delivery. This crucial adaptation can be potentially derailed by inhalation of toxicants. Engineered nanomaterials (ENM) are commonly used in household and industrial products as well as in medicinal applications. As such, the potential risk of exposure remains a concern, especially during pregnancy. We have previously reported that ENM inhalation leads to upregulation in the production of oxidative species. Therefore, we aimed to determine if F0 dam maternal nano-TiO2 inhalation exposure (exclusively) resulted in altered H2O2 production capacity and changes in downstream redox pathways in the F0 dams and subsequent F1 pups. Additionally, we investigated whether this persisted into adulthood within the F1 generation and how this impacted F1 gestational outcomes and F2 fetal health and development. We hypothesized that maternal nano-TiO2 inhalation exposure during gestation in the F0 dams would result in upregulated H2O2 production in the F0 dams as well as her F1 offspring. Additionally, this toxicological insult would result in gestational vascular dysfunction in the F1 dams yielding smaller F2 generation pups. Results Our results indicate upregulation of hepatic H2O2 production capacity in F0 dams, F1 offspring at 8 weeks and F1 females at gestational day 20. H2O2 production capacity was accompanied by a twofold increase in phosphorylation of the redox sensitive transcription factor NF-κB. In cell culture, naïve hepatocytes exposed to F1-nano-TiO2 plasma increased H2O2 production. Overnight exposure of these hepatocytes to F1 plasma increased H2O2 production capacity in a partially NF-κB dependent manner. Pregnant F1- nano-TiO2 females exhibited estrogen disruption (12.12 ± 3.1 pg/ml vs. 29.81 ± 8.8 pg/ml sham-control) and vascular dysfunction similar to their directly exposed mothers. F1-nano-TiO2 uterine artery H2O2 production capacity was also elevated twofold. Dysfunctional gestational outcomes in the F1-nano-TiO2 dams resulted in smaller F1 (10.22 ± 0.6 pups vs. sham-controls 12.71 ± 0.96 pups) and F2 pups (4.93 ± 0.47 g vs. 5.78 ± 0.09 g sham-control pups), and fewer F1 male pups (4.38 ± 0.3 pups vs. 6.83 ± 0.84 sham-control pups). Conclusion In conclusion, this manuscript provides critical evidence of redox dysregulation across generations following maternal ENM inhalation. Furthermore, dysfunctional gestational outcomes are observed in the F1-nano-TiO2 generation and impact the development of F2 offspring. In total, this data provides strong initial evidence that maternal ENM exposure has robust biological impacts that persists in at least two generations.

Maternal nano-titanium dioxide inhalation alters fetoplacental outcomes in a sexually dimorphic manner

“…Females are smaller at GD 20 ( Griffith et al, 2022 ) ( Figure 2A ) and this same pattern of diminished growth persists up to 8-week (data not published). Additionally, adult females (∼10–11 weeks of age) exposed to nano-TiO 2 in utero will also have smaller pups at GD 20 ( Bowdridge et al, 2022 ) and have decreased plasma estrogen levels, which could be due to the decreased JZ area and mass seen in this study. In studies of mouse maternal nano-TiO 2 inhalation exposure during gestation we found that fetal hearts had decreased cardiac output and increased LV mass ( Kunovac et al, 2019 ).…”

“…Additionally, the placentas from nano-TiO 2 exposed dams have increased reactive oxygen species production rate (Bowdridge et al, 2022). Increased reactive oxygen species, like H 2 O 2 , has been shown to increase TXB 2 , the stable TXA 2 metabolite, production in hypertensive rat mesenteric arterioles (Gao and Lee, 2001).…”

“…The maternal side of the vasculature, such as the uterine radial arterioles, have been shown to have reduced vasoreactivity in the presence of vasoactive compounds like prostacyclin or thromboxane ( Griffith et al, 2022 ). Additionally, the placentas from nano-TiO 2 exposed dams have increased reactive oxygen species production rate ( Bowdridge et al, 2022 ). Increased reactive oxygen species, like H 2 O 2 , has been shown to increase TXB 2 , the stable TXA 2 metabolite, production in hypertensive rat mesenteric arterioles ( Gao and Lee, 2001 ).…”

“…Females undergo more placental changes including decreases in mass (JZ and LZ) and area (JZ) when compared to males. These resulting changes may be responsible for the decreased fetal mass seen in females compared to their male counterparts at GD 20, and these changes have been shown to result in health deficits for the females into adulthood ( Bowdridge et al, 2022 ).…”

“…For estimation of lung deposition (dose) with nano-TiO 2 aerosols, equation D = F•V•C•T was used where F is the deposition fraction (10%), V is the minute ventilation (208.3 cc), C is mass concentration (mg/m 3 ), and T equals the exposure duration (minutes) ( Nurkiewicz et al, 2008 ; Stapleton et al, 2013 ). The exposure paradigm (12 mg/m 3 , 6 h/exposure, 6 days) produced a calculated cumulative lung deposition of 525 ± 16 µg ( Bowdridge et al, 2022 ; Griffith et al, 2022 ) with the last exposure occurring on GD19 24-h prior tissue collection. The calculations represent total lung deposition and do not account for lung clearance (MPPD Software v 2.11, Arlington, VA).…”