The prorenin receptor (PRR) was originally proposed to be a member of the renin-angiotensin system (RAS); however, recent work questioned their association. The present paper describes a functional link between the PRR and RAS in the renal juxtaglomerular apparatus (JGA), a classic anatomical site of the RAS. PRR expression was found in the sensory cells of the JGA, the macula densa (MD), and immunohistochemistry-localized PRR to the MD basolateral cell membrane in mouse, rat, and human kidneys. MD cell PRR activation led to MAP kinase ERK1/2 signaling and stimulation of PGE release, the classic pathway of MD-mediated renin release. Exogenous renin or prorenin added to the in vitro microperfused JGA-induced acute renin release, which was inhibited by removing the MD or by the administration of a PRR decoy peptide. To test the function of MD PRR in vivo, we established a new mouse model with inducible conditional knockout (cKO) of the PRR in MD cells based on neural nitric oxide synthase-driven Cre-lox recombination. Deletion of the MD PRR significantly reduced blood pressure and plasma renin. Challenging the RAS by low-salt diet + captopril treatment caused further significant reductions in blood pressure, renal renin, cyclooxygenase-2, and microsomal PGE synthase expression in cKO vs. wild-type mice. These results suggest that the MD PRR is essential in a novel JGA short-loop feedback mechanism, which is integrated within the classic MD mechanism to control renin synthesis and release and to maintain blood pressure.

With the emerging Zika virus (ZIKV) epidemic, accessible real-time reverse transcription-PCR (rRT-PCR) assays are needed to streamline testing. The commercial Altona Diagnostics RealStar ZIKV rRT-PCR test kit (Altona PCR) has been approved for emergency use authorization by the U.S. FDA. Our aim was to verify the Altona PCR by comparing it to the CDC-designed dual-target ZIKV rRT-PCR reference assay (reference PCR) and describe the demographics of patients tested for ZIKV by rRT-PCR in Ontario, Canada. A large set of clinical specimens was tested for ZIKV by the Altona PCR and the reference PCR. Positive or equivocal specimens underwent PCR and Sanger sequencing targeting the ZIKV NS5 gene. A total of 671 serum specimens were tested by the reference PCR: 58 (8.6%) were positive, 193 (28.8%) were equivocal, and 420 (62.6%) were negative. Ninety percent of the reference PCR-positive patients were tested in the first 5 days after symptom onset. The Altona PCR was performed on 284/671 specimens tested by the reference PCR. The Altona PCR was positive for 53/58 (91%) reference PCR-positive specimens and 16/193 (8%) reference PCR-equivocal specimens; the ZIKV NS5 PCR was positive for all 68 Altona PCR-positive specimens and negative for all 181 Altona PCR-negative specimens that underwent the NS5 PCR. The Altona PCR has very good sensitivity (91%) and specificity (97%) compared to the reference PCR. The Altona PCR can be used for ZIKV diagnostic testing and has less extensive verification requirements than a laboratory-developed test.

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Mycoplasma hominis is one of the most common commensal organisms of the genitourinary tract. Immunocompromised patients are susceptible to developing severe infections secondary to M. hominis, and rarely, septic arthritis. This case report describes the occurrence of septic arthritis secondary to M. hominis in a 27-year-old woman with systemic lupus erythematosus (SLE), who presented with a 2-week history of left elbow swelling and tenderness, elevated inflammatory markers and joint aspiration findings consistent with infection. Serial blood cultures were negative. She was treated with flucloxacillin; however, failed to respond and so doxycycline was added to cover for atypical organisms. Subsequently, PCR analysis from the joint aspirate found M. hominis on day 16. Fortunately, doxycycline was an effective treatment for this atypical organism. This case outlines the importance of considering atypical organisms such as M. hominis as a cause of septic arthritis in immunosuppressed patients especially those with SLE.