We have previously shown that neural precursor cell-expressed developmentally downregulated gene 4-2 (Nedd4-2) isoforms with a C2 domain are closely related to ubiquitination of epithelial sodium channel (ENaC), resulting in salt-sensitive hypertension by Nedd4-2 C2 targeting in mice. The sodium voltage-gated channel alpha subunit 5 (SCN5A) gene encodes the α subunit of the human cardiac voltage-gated sodium channel (I Na), and the potassium voltage-gated channel subfamily H member 2 (KCNH2) gene encodes rapidly activating delayed rectifier K channels (I Kr). Both ion channels have also been shown to bind to Nedd4-2 via a conserved Proline-Tyrosine (PY) motif in C-terminal with subsequent ubiquitination and degradation by proteasome. Therefore, loss of Nedd4-2 C2 isoform might be involved in electrophysiological impairment under various conditions. We demonstrate here that Nedd4-2 C2 isoform causes cardiac conduction change in resting condition as well as proarrhythmic change after acute myocardial infarction (MI). The Nedd4-2 C2 knockout (KO) mice showed bradycardia, prolonged QRS, QT intervals, and suppressed PR interval in resting condition. In addition, enhancement of T peak/T end interval was found in mice with surgical ligation of the distal left coronary artery. Morphological analyses based on both ultrasonography of the living heart, as well as histopathological findings revealed that Nedd4-2 C2 KO mice show no significant structural changes from wild-type littermates under resting conditions. These results suggested that Nedd4-2 with C2 domain might play an important role in cardio-renal syndrome through post-transcriptional modification of both ENaC and cardiac ion channels, which are critical for kidney and heart functions.

Post‐orgasmic illness syndrome (POIS) is a rare disease characterized by flu‐like symptoms persisting for 2–7 days after ejaculation. POIS has been chiefly attributed to allergic reactions to autologous seminal plasma. However, the exact pathophysiology remains unclear, and there is no effective treatment. We present the case of a 38‐year‐old man with a 10‐year history of recurrent episodes of flu‐like symptoms of 1‐week duration after ejaculation. The patient was diagnosed with irritating bowel syndrome because of fatigue, myalgia, and lateral abdominal pain. After starting infertility treatment and increasing the frequency of intercourse with his wife, the patient noticed these symptoms after ejaculation. Based on these episodes and symptoms, POIS was suspected. To diagnose POIS, a skin prick test and an intradermal test were performed using his seminal fluid, with the latter yielding a positive result. The patient was diagnosed with POIS, and treatment with antihistamines was continued. Due to its rarity, POIS is often underdiagnosed and underreported; however, the skin test can be a valid diagnostic tool. In this case, the intradermal test result was positive according to the broadly accepted criteria for POIS. Although quality of life is often severely affected in patients with POIS, a lack of a clear understanding of the pathogenesis of POIS prevents early diagnosis. To make diagnoses earlier, it is undoubtedly important to take a detailed medical history and perform skin allergy tests, although the latter requires further validation.

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