Teckman, J. | bioRxiv Science

bioRxiv2020

CHOP-c-JUN complex plays a critical role in liver proteotoxicity induced by mutant Z alpha-1 antitrypsin.

Alpha-1 antitrypsin (AAT) deficiency is a common genetic disorder with lung and liver involvement. Most patients carry the Z allele in SERPINA1 that encodes a mutant AAT (ATZ) forming hepatotoxic polymers. We found CHOP upregulation and activation in both mouse (PiZ) and human livers expressing ATZ. Compared to controls, juvenile PiZ/Chop-/- mice showed reduction in hepatic ATZ and transcriptional response to endoplasmic reticulum stress, as consequence of CHOP-mediated increase of SERPINA1 transcription. CHOP was found to upregulate SERPINA1 though binding with c-JUN on SERPINA1 regulatory elements, thus aggravating hepatic accumulation of ATZ. Increased CHOP levels were detected in diseased livers of children homozygous for the Z allele. Compared to adults, AAT deficiency in infants has different severity and prognosis. Based on our findings, CHOP-c-JUN complex upregulates SERPINA1 transcription and play an important role in the hepatic disease pathogenesis by increasing the burden of proteotoxic ATZ, particularly in the pediatric population.

genetics↗

bioRxiv2019

Alpha-1 Antitrypsin Antisense Oligonucleotide Modulates Protease-Antiprotease Imbalance without Further Aggravating Smoke-induced Lung Injury

Alpha-1 antitrypsin (AAT) is a serum protease inhibitor that prevents lung injury from protease production during cigarette smoking but causes severe liver disease once mutated. A custom AAT antisense oligonucleotide (ASO) was found to be beneficial for the AATD liver disease by blocking the mutated AAT transcripts. Here we hypothesized that knock-down of AAT aggravates murine lung injury during smoke exposure and acute exacerbations of chronic obstructive pulmonary disease (COPD). C57BL/6J mice were randomly divided into 4 groups for each of the injury models, smoking (inhale for 3 months at 150mg/m3) and smoke-flu (inhale for 2 weeks and intranasal influenza virus). The ASO and control (No-ASO) were injected subcutaneously at 10ml/kg of body weight, starting with smoking or four days prior to influenza infection weekly at 50mg/kg. ASO treatment during a 3 month smoke exposure significantly increased the expression of Cela1 mRNA and decreased the serum and lung AAT expression. However, despite the decrease in AAT, neither the inflammatory cell counts in the bronchoalveolar lavage fluid (BALF) nor the lung structural changes were significantly affected by ASO treatment. We observed significant differences in inflammation and emphysema due to smoke exposure alone. With the smoke-flu model, similarly the major differences were found between smoke-flu and room air control, with no additional effect with ASO treatment. Off-target effects or compensatory mechanisms may account for this finding. Alternatively, the reduction of AAT with ASO treatment was not robust enough to lead to lung injury. The result also suggest that the AAT ASO approach for treating liver disease is relatively safe at the specified dose as it did not lead to detrimental outcomes in the lung. These potential mechanisms need to be further investigated in order to fully understand the impact of AAT inhibition on protease-antiprotease imbalance in the murine smoke exposure model.

physiology↗