Although animal models have been evaluated for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, none have fully recapitulated the lung disease phenotypes seen in humans who have been hospitalized. Here, we evaluate transgenic mice expressing the human angiotensin I-converting enzyme 2 (ACE2) receptor driven by the cytokeratin-18 (K18) gene promoter (K18-hACE2) as a model of SARS-CoV-2 infection. Intranasal inoculation of SARS-CoV-2 in K18-hACE2 mice results in high levels of viral infection in lungs, with spread to other organs. A decline in pulmonary function occurs 4 days after peak viral titer and correlates with infiltration of monocytes, neutrophils and activated T cells. SARS-CoV-2-infected lung tissues show a massively upregulated innate immune response with signatures of nuclear factor-κB-dependent, type I and II interferon signaling, and leukocyte activation pathways. Thus, the K18-hACE2 model of SARS-CoV-2 infection shares many features of severe COVID-19 infection and can be used to define the basis of lung disease and test immune and antiviral-based countermeasures.

We determined the effect of inhaled corticosteroid, budesonide, on the release of the anti-inflammatory cytokine, interleukin-10 (IL-10), and of pro-inflammatory cytokines, macrophage inflammatory protein-1alpha (MIP-1alpha), interferon-gamma (IFN-gamma), and granulocyte-macrophage colony-stimulating factor (GM-CSF), from blood monocytes and alveolar macrophages of mild asthmatic subjects in a double-blind, cross-over, placebo-controlled study. Budesonide reduced bronchial hyperresponsiveness and improved baseline FEV1. Alveolar macrophages were obtained by bronchoalveolar lavage performed at the end of each treatment phase. IL-10 from blood monocytes was not altered, but both IL-10 mRNA and protein expression from alveolar macrophages stimulated by lipopolysaccharide and IL-1beta were increased after corticosteroid therapy. By contrast, alveolar macrophages released significantly less MIP-1alpha, IFN-gamma, and GM-CSF after steroid treatment. In comparison to alveolar macrophages from normal nonasthmatic volunteers, those from asthmatic patients released more MIP-1alpha, IFN-gamma, and GM-CSF but lower amounts of IL-10 particularly at baseline and after IL-1beta stimulation. The ability of steroids to inhibit pro-inflammatory cytokines but to enhance the anti-inflammatory cytokine such as IL-10 may contribute to their beneficial actions in asthma. Asthma is characterized by alveolar macrophages exhibiting both an enhanced capacity to release pro-inflammatory cytokines and a reduced capacity to produce IL-10.

Rationale-IL-9 is a pleiotropic cytokine that has multiple effects on structural as well as numerous hematopoietic cells, which are central to the pathogenesis of asthma.Objectives-The contribution of IL-9 to asthma pathogenesis has thus far been unclear, due to conflicting reports in the literature. These earlier studies focused on the role of IL-9 in acute inflammatory models; here we have investigated the effects of IL-9 blockade during chronic allergic inflammation.Methods-Mice were exposed to either prolonged ovalbumin or house dust mite allergen challenge to induce chronic inflammation and airway remodeling.

A combination of pharmacological and genetic approaches was used to determine the role of type 4 cAMP-specific cyclic nucleotide phosphodiesterase 4 (PDE4) in reversing alpha(2)-adrenoceptor-mediated anesthesia, a behavioral correlate of emesis in non-vomiting species. Among the family-specific PDE inhibitors, PDE4 inhibitors reduced the duration of xylazine/ketamine-induced anesthesia in mice, with no effect on pentobarbital-induced anesthesia. The rank order of the PDE4 inhibitors tested was 6-(4-pyridylmethyl)-8-(3-nitrophenyl)quinoline (PMNPQ) > (R)-rolipram > (S)-rolipram >> (R)-N-[4-[1-(3-cyclopentyloxy-4-methoxyphenyl)-2-(4-pyridyl)ethyl]phenyl]N'-ethylurea (CT-2450). The specific roles of PDE4B and PDE4D in this model were studied using mice deficient in either subtype. PDE4D-deficient mice, but not PDE4B-deficient mice, had a shorter sleeping time than their wild-type littermates under xylazine/ketamine-induced anesthesia, but not under that induced with pentobarbital. Concomitantly, rolipram-sensitive PDE activity in the brain stem was decreased only in PDE4D-deficient mice compared with their wild-type littermates. While PMNPQ significantly reduced the xylazine/ketamine-induced anesthesia period in wild-type mice and in PDE4B-null mice, it had no effect in PDE4D-deficient mice. These findings strongly support the hypothesis that inhibition of PDE4D is pivotal to the anesthesia-reversing effect of PMNPQ and is likely responsible for emesis induced by PDE4 inhibitors.

IntroductionCyclic nucleotides cAMP and cGMP are degraded by at least 11 families of phosphodiesterases (PDEs 1-11) classified according to their gene sequence, substrate specificity, biochemical regulation, and sensitivity to inhibitors (1, 2). The cAMP-specific PDE4 has attracted considerable attention for the treatment of airway inflammatory diseases, since its inhibition results in attenuated inflammatory responses (1,3,4). However, the therapeutic potential of PDE4 inhibitors has been limited by the side effects of nausea and emesis, observed both in humans and in various animal species following the administration of structurally diverse compounds (5-9). A major challenge in the development of new generations of PDE4 inhibitors is the improvement of the therapeutic index of this class of compounds.PDE4 enzymes use a common binuclear ion center as the core catalytic machinery (10). The reversible binding of the cation cofactors (e.g., Mg 2+ ) results in the presence of two coexisting conformers that bind inhibitors differently: the holoenzyme (enzyme bound with Mg 2+ ) and the apoenzyme (free enzyme) (11,12). In the past, it was observed that the potency of some inhibitors (e.g., rolipram) on PDE activity deviated from their affinity at the high-affinity rolipram binding site (HARBS); this led to the proposal that inhibitors with a reduced potency on the HARBS may have an improved therapeutic index over that of firstgeneration compounds (13-15). It has now been clarified that the HARBS corresponds to the holoenzyme conformer responsible for PDE4 catalysis (11,12).The PDE4 family is composed of four subtypes (PDE4A-D) and multiple splice variants (16). If it were possible to identify the subtype(s) responsible for the beneficial and the side effects associated with PDE4 inhibition, then subtype-selective inhibitors devoid of the tendency to induce nausea and vomiting could be developed. The mechanism of the emetic response associated with PDE4 inhibitors is thought to be a consequence of the inhibition of PDE4 in nontarget tissues (9, 13). It is believed that PDE4 inhibitors produce a pharmacologi- A combination of pharmacological and genetic approaches was used to determine the role of type 4 cAMP-specific cyclic nucleotide phosphodiesterase 4 (PDE4) in reversing α 2 -adrenoceptor-mediated anesthesia, a behavioral correlate of emesis in non-vomiting species. Among the family-specific PDE inhibitors, PDE4 inhibitors reduced the duration of xylazine/ketamine-induced anesthesia in mice, with no effect on pentobarbital-induced anesthesia. The rank order of the PDE4 inhibitors tested was 6-(4- -2450). The specific roles of PDE4B and PDE4D in this model were studied using mice deficient in either subtype. PDE4D-deficient mice, but not PDE4B-deficient mice, had a shorter sleeping time than their wild-type littermates under xylazine/ketamine-induced anesthesia, but not under that induced with pentobarbital. Concomitantly, rolipram-sensitive PDE activity in the brain stem was decreased only in PDE4D-deficient mice c...