Olfactory receptors impact pathophysiological processes of lung diseases in bronchial epithelial cells.

BACKGROUND: Therapeutic options for steroid-resistant non-type 2 inflammation in obstructive lung diseases are limited. Bronchial epithelial cells are key in the pathogenesis by releasing the central proinflammatory cytokine interleukine-8 (IL-8). Olfactory receptors (ORs) are expressed in various cell types. This study examined the drug target potential of ORs by investigating their impact on associated pathophysiological processes in lung epithelial cells. METHODS: Experiments were performed in the A549 cell line and in primary human bronchial epithelial cells. OR expression was investigated using RT-PCR, Western blot, and immunocytochemical staining. OR-mediated effects were analyzed by measuring 1) intracellular calcium concentration via calcium imaging, 2) cAMP concentration by luminescence-based assays, 3) wound healing by scratch assays, 4) proliferation by MTS-based assays, 5) cellular vitality by Annexin V/PI-based FACS staining, and 6) the secretion of IL-8 in culture supernatants by ELISA. RESULTS: By screening 100 potential OR agonists, we identified two, Brahmanol and Cinnamaldehyde, that increased intracellular calcium concentrations. The mRNA and proteins of the corresponding receptors OR2AT4 and OR2J3 were detected. Stimulation of OR2J3 with Cinnamaldehyde reduced 1) IL-8 in the absence and presence of bacterial and viral pathogen-associated molecular patterns (PAMPs), 2) proliferation, and 3) wound healing but increased cAMP. In contrast, stimulation of OR2AT4 by Brahmanol increased wound healing but did not affect cAMP and proliferation. Both ORs did not influence cell vitality. CONCLUSION: ORs might be promising drug target candidates for lung diseases with non-type 2 inflammation. Their stimulation might reduce inflammation or prevent tissue remodeling by promoting wound healing.

OR2AT4 and OR1A2 counterregulate molecular pathophysiological processes of steroid-resistant inflammatory lung diseases in human alveolar macrophages.

BACKGROUND: Therapeutic options for steroid-resistant non-type 2 inflammation in obstructive lung diseases are lacking. Alveolar macrophages are central in the progression of these diseases by releasing proinflammatory cytokines, making them promising targets for new therapeutic approaches. Extra nasal expressed olfactory receptors (ORs) mediate various cellular processes, but clinical data are lacking. This work investigates whether ORs in human primary alveolar macrophages could impact pathophysiological processes and could be considered as therapeutic targets. METHODS: Human primary alveolar macrophages were isolated from bronchoalveolar lavages of 50 patients with pulmonary diseases. The expression of ORs was validated using RT-PCR, immunocytochemical staining, and Western blot. Changes in intracellular calcium levels were analyzed in real-time by calcium imaging. A luminescent assay was used to measure the cAMP concentration after OR stimulation. Cytokine secretion was measured in cell supernatants 24 h after stimulation by ELISA. Phagocytic ability was measured by the uptake of fluorescent-labeled beads by flow cytometry. RESULTS: We demonstrated the expression of functional OR2AT4 and OR1A2 on mRNA and protein levels. Both ORs were primarily located in the plasma membrane. Stimulation with Sandalore, the ligand of OR2AT4, and Citronellal, the ligand of OR1A2, triggered a transient increase of intracellular calcium and cAMP. In the case of Sandalore, this calcium increase was based on a cAMP-dependent signaling pathway. Stimulation of alveolar macrophages with Sandalore and Citronellal reduced phagocytic capacity and release of proinflammatory cytokines. CONCLUSION: These are the first indications for utilizing olfactory receptors as therapeutic target molecules in treating steroid-resistant lung diseases with non-type 2 inflammation.

Effects of Quinine, Quinidine and Chloroquine on Human Muscle Nicotinic Acetylcholine Receptors.

The genus Cinchona is known for a range of alkaloids, such as quinine, quinidine, cinchonine, and cinchonidine. Cinchona bark has been used as an antimalarial agent for more than 400 years. Quinine was first isolated in 1820 and is still acknowledged in the therapy of chloroquine-resistant falciparum malaria; in lower dosage quinine has been used as treatment for leg cramps since the 1940s. Here we report the effects of the quinoline derivatives quinine, quinidine, and chloroquine on human adult and fetal muscle nicotinic acetylcholine receptors (nAChRs). It could be demonstrated that the compounds blocked acetylcholine (ACh)-evoked responses in Xenopus laevis oocytes expressing the adult nAChR composed of αß𝜀δ subunits in a concentration-dependent manner, with a ranked potency of quinine (IC50 = 1.70 µM), chloroquine (IC50 = 2.22 µM) and quinidine (IC50 = 3.96 µM). At the fetal nAChR composed of αßγδ subunits, the IC50 for quinine was found to be 2.30 µM. The efficacy of the block by quinine was independent of the ACh concentration. Therefore, quinine is proposed to inhibit ACh-evoked currents in a non-competitive manner. The present results add to the pharmacological characterization of muscle nAChRs and indicate that quinine is effective at the muscular nAChRs close to therapeutic blood concentrations required for the therapy and prophylaxis of nocturnal leg cramps, suggesting that the clinically proven efficacy of quinine could be based on targeting nAChRs.