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Background Olaparib, a poly (ADP-ribose) polymerase (PARP) inhibitor, has demonstrated effectiveness in treating ovarian, breast, and other cancers, particularly those with specific molecular subtypes including, but not limited to, BRCA1/2 mutations. Consequently, its utilization is expected to increase in the future. For this reason, it is important to acknowledge the potential for adverse events associated with olaparib, including the relatively rare but significant risk of drug-induced interstitial lung disease (DIILD). Since DIILD can lead to fatal outcomes, its early detection is crucial. The dissemination of knowledge regarding DIILD can be facilitated through case reports; however, specific reports of DIILD caused by olaparib have only been published in Japanese. To the best of our knowledge, this is the first report in English of our experience with three cases of DIILD caused by olaparib. Case presentation Cases 1, 2, and 3 involved Japanese women with ovarian cancer who had been receiving olaparib at a dose of 600 mg/day. Case 1, a 72-year-old woman who had been on olaparib for 4 months, and case 2, a 51-year-old woman who had been on olaparib for 8 months, reported fever and general malaise. Chest computed tomography (CT) revealed pale ground glass opacity (GGO) similar to hypersensitivity pneumonitis. The severity grade was 2 in both cases. Case 3, a 78-year-old woman who had been on olaparib for 3 weeks, presented with cough and reported dyspnea on exertion. Chest CT revealed non-specific interstitial pneumonia and organizing pneumonia-like shadows. The severity grade was 4. Olaparib was discontinued in all cases. Case 1 received 0.6 mg/kg of prednisolone due to mild hypoxia, while prednisolone was not administered in case 2 due to the absence of hypoxia. Case 3 received steroid pulse therapy due to severe hypoxia. Olaparib administration was not resumed in any patient. Conclusion DIILD caused by olaparib in Japan, including the present three cases, commonly presents with GGO, similar to hypersensitivity pneumonitis on chest CT. The prognosis for the majority of patients is favorable; however, there have been instances of severe cases. Early recognition of drug-induced lung injury and further accumulation of cases is important.

We have previously shown that endoplasmic reticulum stress (ER stress) represses the PTEN inducible kinase 1 (PINK1) in lung type II alveolar epithelial cells (AECII) reducing mitophagy and increasing the susceptibility to lung fibrosis. Although increased circulating mitochondrial DNA (mtDNA) has been reported in chronic lung diseases, the contribution of mitophagy in the modulation of mitochondrial DAMP release and activation of profibrotic responses is unknown. In this study, we show that ER stress and PINK1 deficiency in AECII led to mitochondrial stress with significant oxidation and damage of mtDNA and subsequent extracellular release. Extracellular mtDNA was recognized by TLR9 in AECII by an endocytic-dependent pathway. PINK1 deficiency-dependent mtDNA release promoted activation of TLR9 and triggered secretion of the profibrotic factor TGF-β which was rescued by PINK1 overexpression. Enhanced mtDNA oxidation and damage were found in aging and IPF human lungs and, in concordance, levels of circulating mtDNA were significantly elevated in plasma and bronchoalveolar lavage (BAL) from patients with IPF. Free mtDNA was found elevated in other ILDs with low expression of PINK1 including hypersensitivity pneumonitis and autoimmune interstitial lung diseases. These results support a role for PINK1 mediated mitophagy in the attenuation of mitochondrial damage associated molecular patterns (DAMP) release and control of TGF-β mediated profibrotic responses.

Fibrotic hypersensitivity pneumonitis is a complex interstitial lung disease that is not entirely understood. In its chronic and fibrotic form, hypersensitivity pneumonitis is one of the main mimickers of idiopathic pulmonary fibrosis (IPF). Distinguishing between these two conditions is challenging but is of particular clinical relevance. Two approved therapies are available for IPF, and a considerable number of clinical trials are now exploring newer pharmacological options. This impressive research effort is a consequence of new pathogenetic understanding, updated diagnostic criteria and a long history of pharmacological trials. Conversely, current knowledge gaps on pathogenesis of chronic hypersensitivity pneumonitis, coupled with lack of validated diagnostic criteria, make the management of this disease an unsolved clinical challenge. This also reflects the paucity of therapeutic clinical trials in this field. In this review, we describe the current evidence and the possible future options to approach this complex disease.

Hypersensitivity pneumonitis (HP) is an interstitial lung disease that develops following repeated exposure to environmental antigens. The disease results in alveolitis, granuloma formation and may progress to a fibrotic chronic form, which is associated with significant morbidity and mortality. The severity of the disease correlates with a neutrophil rich influx and an IL-17 response. We used the Saccharopolysporarectivirgula (SR) model of HP to determine whether Toll-like receptors (TLR) 2 and 9 cooperate in neutrophil recruitment and IL-17-associated cytokine production during the development of HP. Stimulation of bone marrow derived macrophages (BMDMs) from C57BL/6, MyD88(-/-) and TLR2/9(-/-) mice with SR demonstrate that SR is a strong inducer of neutrophil chemokines and growth factors. The cytokines induced by SR were MyD88-dependent and, of those, most were partially or completely dependent on TLRs 2 and 9. Following in vivo exposure to SR, CXCL2 production and neutrophil recruitment were reduced in TLR2(-/-) and TLR2/9(-/-) mice suggesting that the response was largely dependent on TLR2; however the reduction was greatest in the TLR2/9(-/-) double knockout mice indicating TLR9 may also contribute to the response. There was a reduction in the levels of pro-inflammatory cytokines TNFα and IL-6 as well as CCL3 and CCL4 in the BALF from TLR2/9(-/-) mice compared to WT and single knockout (SKO) mice exposed one time to SR. The decrease in neutrophil recruitment and TNFα production in the TLR2/9(-/-) mice was maintained throughout 3 weeks of SR exposures in comparison to WT and SKO mice. Both TLRs 2 and 9 contributed to the Th17 response; there was a decrease in Th17 cells and IL-17 mRNA in the TLR2/9(-/-) mice in comparison to the WT and SKO mice. Despite the effects on neutrophil recruitment and the IL-17 response, TLR2/9(-/-) mice developed granuloma formation similarly to WT and SKO mice suggesting that there are additional mediators and pattern recognition receptors involved in the disease.