Organelle communication maintains mitochondrial and endosomal homeostasis during podocyte lipotoxicity.

Organelle stress exacerbates podocyte injury, contributing to perturbed lipid metabolism. Simultaneous organelle stresses can occur in the kidney in the diseased state; therefore, a thorough analysis of organelle communication is crucial for understanding the progression of kidney diseases. Although organelles closely interact with one another at membrane contact sites, limited studies have explored their involvement in kidney homeostasis. The endoplasmic reticulum (ER) protein, PDZ domain-containing 8 (PDZD8), is implicated in multiple-organelle-tethering processes and cellular lipid homeostasis. In this study, we aimed to elucidate the role of organelle communication in podocyte injury using podocyte-specific Pdzd8-knockout mice. Our findings demonstrated that Pdzd8 deletion exacerbated podocyte injury in an accelerated obesity-related kidney disease model. Proteomic analysis of isolated glomeruli revealed that Pdzd8 deletion exacerbated mitochondrial and endosomal dysfunction during podocyte lipotoxicity. Additionally, electron microscopy revealed the accumulation of abnormal, fatty endosomes in Pdzd8-deficient podocytes during obesity-related kidney diseases. Lipidomic analysis indicated that glucosylceramide accumulated in Pdzd8-deficient podocytes, owing to accelerated production and decelerated degradation. Thus, the organelle-tethering factor, PDZD8, plays a crucial role in maintaining mitochondrial and endosomal homeostasis during podocyte lipotoxicity. Collectively, our findings highlight the importance of organelle communication at the 3-way junction among the ER, mitochondria, and endosomes in preserving podocyte homeostasis.

Renal recovery following daratumumab, lenalidomide, and dexamethasone therapy in a patient with newly diagnosed dialysis-dependent multiple myeloma.

An 81-year-old Japanese woman was diagnosed with Bence Jones protein κ-type multiple myeloma with acute kidney injury and severe anemia, complicated by congestive heart failure with triple vessel coronary artery disease. Her serum κ-free light-chain (FLC) level was 49,400 mg/L and κ/λ ratio was extremely high at 2373. Her kidney function deteriorated rapidly and required hemodialysis before initiating chemotherapy. A combination therapy of daratumumab (16 mg/kg), lenalidomide, and dexamethasone was initiated as a first-line treatment; the infusion rate of daratumumab was adjusted to reduce the heart load. The level of κ-FLC was rapidly reduced by 75% in only one week and by 99% after three weeks. Furthermore, she was dialysis-independent after the fourth dose of daratumumab. We report the first case of untreated patient with myeloma who had been successfully treated with daratumumab, lenalidomide, and dexamethasone therapy even in dialysis requiring state. Daratumumab may benefit patients with acute kidney injury caused by multiple myeloma, owing to the immediate need of FLC level reduction. Daratumumab and lenalidomide combination therapy could be a valuable treatment option for patients requiring dialysis when bortezomib may be hesitate to use due to severe heart disease.

The effect of trichlormethiazide in autosomal dominant polycystic kidney disease patients receiving tolvaptan: a randomized crossover controlled trial.

The vasopressin V2 receptor antagonist tolvaptan delays the progression of autosomal dominant polycystic kidney disease (ADPKD). However, some patients discontinue tolvaptan because of severe adverse aquaretic events. This open-label, randomized, controlled, counterbalanced, crossover trial investigated the effects of trichlormethiazide, a thiazide diuretic, in patients with ADPKD receiving tolvaptan (n = 10) who randomly received antihypertensive therapy with or without trichlormethiazide for 12 weeks. The primary and secondary outcomes included amount and osmolarity of 24-h urine and health-related quality-of-life (HRQOL) parameters assessed by the Kidney Disease Quality of Life-Short Form questionnaire, renal function slope, and plasma/urinary biomarkers associated with disease progression. There was a significant reduction in urine volume (3348 ± 584 vs. 4255 ± 739 mL; P < 0.001) and a significant increase in urinary osmolarity (182.5 ± 38.1 vs. 141.5 ± 38.1 mOsm; P = 0.001) in patients treated with trichlormethiazide. Moreover, trichlormethiazide improved the following HRQOL subscales: effects of kidney disease, sleep, emotional role functioning, social functioning, and role/social component summary. No significant differences were noted in renal function slope or plasma/urinary biomarkers between patients treated with and without trichlormethiazide. In patients with ADPKD treated with tolvaptan, trichlormethiazide may improve tolvaptan tolerability and HRQOL parameters.

Bortezomib-induced glomerular microangiopathy complicated with monoclonal immunoglobulin deposition disease.

A 75-year-old man admitted with IgG λ-type myeloma with creatinine level of 2.3 mg/dL. Serum lactate dehydrogenase level and platelet count were normal. Urinalysis demonstrated massive proteinuria dominated by albuminuria. Weekly bortezomib and dexamethasone therapy were started to treat myeloma but failed to be continued because of rapid deterioration of renal function and increase in proteinuria 1 week after the treatment. His renal function exacerbated to require hemodialysis for a month. There was no clinical evidence of tumor lysis syndrome or thrombocytopenia throughout the course of his acute kidney injury (AKI). After he became dialysis independent, a renal biopsy was performed to clarify myeloma-related renal involvement and the cause of AKI. As a result, IgG2-λ monoclonal immunoglobulin deposition disease (MIDD) and severe endothelial injury were revealed. There was no evidence of cast nephropathy. Bortezomib-induced glomerular microangiopathy (GMA) superimposed on MIDD. Bortezomib has a potential risk to cause drug-induced GMA without systemic thrombotic microangiopathy, in which vascular endothelial growth factor-nuclear factor-κ B pathway could be involved. This is the first case of biopsy-proven bortezomib-induced GMA. If proteinuria (mainly albuminuria) increases after using bortezomib, GMA should be suspected as an adverse effect of bortezomib even absent of clinical signs of systemic thrombotic microangiopathy.

Successful management of hemodialysis-dependent refractory myeloma with modified daratumumab, bortezomib and dexamethasone regimen.

A 71-year-old petite Japanese woman was diagnosed with IgG λ-type multiple myeloma with acute kidney injury, severe anemia, and a pathological rib fracture. Emergent hemodialysis was initiated combined with chemotherapy including bortezomib, lenalidomide, and pomalidomide, but myeloma had become refractory due to the treatments. Therefore, a combination therapy with weekly daratumumab (16 mg/kg), bortezomib (0.7 mg/m2), and dexamethasone was started. Daratumumab was administered on a non-dialysis day with a reduced infusion speed to avoid acute water load. No infusion-related adverse events were observed throughout the treatment. Daratumumab and bortezomib were administrated weekly for three times in the first cycle and a hematological very good partial response was achieved. Then, the treatment schedule was reduced to once every three weeks from the 2nd cycle, the very good partial response had been maintained. Fourteen months after the initiation of maintenance hemodialysis, the patient was able to reduce dialysis frequency due to improvement of renal function. A modified daratumumab, bortezomib and dexamethasone regimen could be a valuable treatment option for dialysis-dependent myeloma patients.