Panigrahy, Nisha

Airway inflammation and pro-inflammatory cytokines such as tumor necrosis factor alpha (TNFα) underlie the pathophysiology of respiratory diseases, including asthma. Previously, we showed that TNFα selectively activates the inositol-requiring enzyme 1α (IRE1α)/X-box binding protein 1 spliced (XBP1s) ER stress pathway in human airway smooth muscle (hASM) cells. The ER stress pathway is activated by the accumulation of unfolded proteins in the ER. Accordingly, chemical chaperones such as 4-phenylbutyrate (4-PBA) may ameliorate ER stress activation. In the present study, we hypothesize that 4-PBA mitigates TNFα induced ER stress in hASM cells. hASM cells were isolated from bronchiolar tissue obtained from 5 donors with no history of current smoking or respiratory diseases. hASM cells were serum-deprived for 48 h, and phenotype confirmed by expression of smooth muscle actin and fusiform morphology. hASM cells from the same donor were then separated into 4 12-h treatment groups: 1) TNFα (20 ng/mL), 2) TNFα + 4-PBA (30 min pretreatment), and 3) untreated control. Protein expression and phosphorylation of IRE1α and XBP1s were determined by Western blot. Gene expression of XBP1s was analyzed by PCR. We found that TNFα induced IRE1α phosphorylation and XBP1 splicing, which were significantly reduced by pretreatment with 4-PBA. These results support our hypothesis and suggest that, in the presence of chemical chaperone 4-PBA, TNFα induced ER stress is significantly decreased. R01HL 157984 (GCS) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The impact of airway inflammation is mediated by pro-inflammatory cytokines such as tumor necrosis factor alpha (TNFα), which underlies several respiratory diseases, including COVID-19, asthma, chronic bronchitis, and chronic obstructive pulmonary disease (COPD). In human airway smooth muscle (hASM) cells, exposure to TNFα leads to an accumulation of unfolded proteins in the ER, which triggers a homeostatic ER stress response activating a signaling cascade to restore normal function. Previously, we showed that TNFα selectively activates the inositol-requiring enzyme 1α (IRE1α)/X-box binding protein 1 (XBP1) ER stress pathway in hASM cells. Most likely, the protein unfolding in hASM cells caused by TNFα results from an increase in reactive oxygen species (ROS) formation. We hypothesize that ER stress induced by TNFα is mitigated by the ROS scavenger TEMPOL. Primary hASM cells were isolated from bronchiolar tissue samples obtained from 5 patients (both sexes included) who had no history of respiratory diseases. hASM cells were serum deprived for 48 h before treatment with 1) TNFα (20 ng/ml) for 12 h; 2) TEMPOL (500 μM) for 30 min followed by TNFα (20 ng/ml) for 12 h; and 3) untreated control for 12 h. At the end of the treatment period, hASM cells were processed for determination of protein expression through Western blotting. Activation of the ER stress response was assessed by phosphorylation of IRE1α and splicing of XBP1. Confirming our previous results, we found that 12 h TNFα exposure induced an ER stress response in hASM cells, evidence by phosphorylation of IRE1α and XBP1 splicing. Treating hASM cells with TEMPOL before exposure to TNFα mitigated the ER stress response. These results support our hypothesis and indicate that ROS scavenging prevents TNFα induced protein unfolding and triggering of the IRE1α/XBP1 ER stress pathway. R01HL 157984 (GCS) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.