TLR4 and pulmonary arterial hypertension: In addition, in this animal model of pulmonary arterial hypertension, males also showed higher TLR4 protein expression in lungs when compared to females, suggesting that the larger activation of the HMGB1/TLR4 axis may contribute to the worse outcomes of pulmonary arterial hypertension observed in males (Zemskova et al., 2020).