The role of phosphodiesterase in the regulation of Streptococcus pneumoniae drug sensitivity and the therapeutic effect of its inhibitors in mice

The emergence of drug-resistant Streptococcus pneumoniae has become a global health challenge, particularly as a major causative agent of community-acquired pneumonia. Cyclic dimeric adenosine monophosphate (c-di-AMP), a pivotal bacterial second messenger, is known to regulate key physiological processes such as drug resistance in multiple streptococci species. However, its precise role in S. pneumoniae drug resistance remains unclear. This study found that pde1 and pde2, encoding phosphodiesterases (PDEs) of c-di-AMP, regulated morphology, growth and drug sensitivity of S. pneumoniae. Mutation of pde2 significantly increased drug sensitivity to several antibiotics, despite only minor changes in c-di-AMP levels and inconsistent expression shifts in resistance-related genes. Further, a clinical isolate with pde2 mutant showed a higher c-di-AMP level and was more sensitive to several antibiotics, and the mutant PDE2 from S. pneumoniae clinical strain showed reduced phosphodiesterase activity. Moreover, sildenafil, an FDA-approved PDE inhibitor, increased drug sensitivity of clinical resistant S. pneumoniae in vitro, and effectively suppressed bacterial growth and the inflammatory response in mice infected with resistant S. pneumoniae. infected mice. These results suggested that PDE2 could be used as a drug target against resistant S. pneumoniae.

耐药肺炎链球菌（drug-resistant Streptococcus pneumoniae）的出现已成为全球性公共卫生挑战，其作为社区获得性肺炎的主要致病菌尤为值得关注。环二腺苷单磷酸（cyclic dimeric adenosine monophosphate, c-di-AMP）作为一类关键的细菌第二信使，已被证实可调控多种链球菌属物种的耐药性等核心生理过程。然而，其在肺炎链球菌耐药性中的具体作用仍不明晰。本研究发现，编码c-di-AMP磷酸二酯酶（phosphodiesterases, PDEs）的pde1与pde2基因，可调控肺炎链球菌的形态、生长及药物敏感性。尽管pde2突变仅引起c-di-AMP水平小幅变化，且耐药相关基因的表达改变并不一致，但该突变可显著提升肺炎链球菌对多种抗生素的敏感性。此外，一株携带pde2突变的临床分离株的c-di-AMP水平更高，且对多种抗生素更为敏感；源自肺炎链球菌临床菌株的突变型PDE2的磷酸二酯酶活性有所降低。进一步研究显示，西地那非——一种获美国食品药品监督管理局（FDA）批准的PDE抑制剂——可在体外提升临床耐药肺炎链球菌的药物敏感性，并可有效抑制耐药肺炎链球菌感染小鼠体内的细菌增殖与炎症反应。上述研究结果表明，PDE2可作为抗耐药肺炎链球菌的药物作用靶点。