Edward Calomeni

Acute kidney injury during warfarin therapy associated with obstructive tubular red blood cell casts: a report of 9 cases.

Acute kidney injury (AKI) during warfarin therapy usually is hemodynamic secondary to massive blood loss. Here, we report pathological findings in kidney biopsy specimens from 9 patients with warfarin overdose, hematuria, and AKI. Kidney biopsy specimens from patients on warfarin therapy with AKI were identified in our database within a 5-year period. Each kidney biopsy specimen was evaluated by using semiquantitative morphometric techniques, and medical history was reviewed for conditions explaining AKI. Biopsy specimens with morphological findings of active glomerulonephritis and active inflammatory lesions were excluded from the study. Biopsy specimens from 9 patients were selected. At presentation with AKI, each patient had an abnormal international normalized ratio (mean 4.4 +/- 0.7 IU) and increased serum creatinine level (mean, 4.3 +/- 0.8 mg/dL). Morphologically, each biopsy specimen showed evidence of acute tubular injury and glomerular hemorrhage: red blood cells (RBCs) in Bowman space and numerous occlusive RBC casts in tubules. Each biopsy specimen showed chronic kidney injury. Six of 9 patients did not recover from AKI. These data suggest that warfarin therapy can result in AKI by causing glomerular hemorrhage and renal tubular obstruction by RBC casts. Our experience suggests that this may be a potentially serious complication of warfarin therapy, especially in older patients with underlying chronic kidney injury.

Inhibition of collagen fibrillogenesis by cells expressing soluble extracellular domains of DDR1 and DDR2.

Collagen fiber assembly affects many physiological processes and is tightly controlled by collagen-binding proteins. However, to what extent membrane-bound versus cell-secreted collagen-binding proteins affect collagen fibrillogenesis is not well understood. In our previous studies, we had demonstrated that the membrane-anchored extracellular domain (ECD) of the collagen receptor discoidin domain receptor 2 (DDR2) inhibits fibrillogenesis of collagen endogenously secreted by the cells. These results led to a novel functional role of the DDR2 ECD. However, since soluble forms of DDR1 and DDR2 containing its ECD are known to naturally exist in the extracellular matrix, in this work we investigated if these soluble DDR ECDs may have a functional role in modulating collagen fibrillogenesis. For this purpose, we created mouse osteoblast cell lines stably secreting DDR1 or DDR2 ECD as soluble proteins. Transmission electron microscopy, fluorescence microscopy, and hydroxyproline assays were used to demonstrate that DDR ECD expression reduced the rate and quantity of collagen deposition and induced significant changes in fiber morphology and matrix mineralization. Collectively, our studies advance our understanding of DDR receptors as powerful regulators of collagen deposition in the ECM and elucidate their multifaceted role in ECM remodeling.

5/6 nephrectomy as a validated rat model mimicking human warfarin-related nephropathy.

Background/Aims: We previously reported that patients with chronic kidney disease (CKD) receiving warfarin therapy and whose international normalized ratio increases to >3.0 may develop acute kidney injury (AKI) as a result of glomerular hemorrhage and formation of obstructive red blood cell (RBC) casts. We named this condition warfarin-related nephropathy (WRN). We also previously reported that acute excessive anticoagulation with brodifacoum (superwarfarin) induces AKI in 5/6 nephrectomy (5/6NE) rats. Limitations of the brodifacoum model precluded a careful assessment of dose-response relationships. Methods: Warfarin treatment was used in 5/6NE. Results: Herein we report that warfarin treatment of 5/6NE rats resulted in a dose-dependent increase in serum creatinine (SC). The increase in SC following warfarin treatment was greater at 3 and 19 weeks after the ablative surgery, than that observed 8 weeks after the ablative surgery. The SC increase was correlated with the prothrombin time increase. Morphologically, 5/6NE, but not control rats, had acute tubular injury with RBC and RBC casts in the tubules. Treatment with vitamin K prevented SC increase and morphologic changes in the kidney associated with warfarin treatment. A single episode of WRN did not affect the progression of CKD in 5/6NE. Conclusion: (1) The 5/6NE model of CKD is an appropriate animal model to study the pathogenesis of WRN. (2) The pharmacokinetics of warfarin is better suited to the study of WRN than that of brodifacoum. (3) The more advanced stages of 5/6NE are more susceptible to WRN than the earlier stages. (4) Vitamin K treatment prevents WRN.

Regulation Of Collagen Fibrillogenesis By Cell Surface Expression Of Kinase Dead DDR2

The assembly of collagen fibers, the major component of the extracellular matrix (ECM), governs a variety of physiological processes. Collagen fibrillogenesis is a tightly controlled process in which several factors, including collagen binding proteins, have a crucial role. Discoidin domain receptors (DDR1 and DDR2) are receptor tyrosine kinases that bind to and are phosphorylated upon collagen binding. The phosphorylation of DDRs is known to activate matrix metalloproteases, which in turn cleave the ECM. In our earlier studies, we established a novel mechanism of collagen regulation by DDRs; that is, the extracellular domain (ECD) of DDR2, when used as a purified, soluble protein, inhibits collagen fibrillogenesis in-vitro. To extend this novel observation, the current study investigates how the DDR2-ECD, when expressed as a membrane-anchored, cell-surface protein, affects collagen fibrillogenesis by cells. We generated a mouse osteoblast cell line that stably expresses a kinase-deficient form of DDR2, termed DDR2/-KD, on its cell surface. Transmission electron microscopy, fluorescence microscopy, and hydroxyproline assays demonstrated that the expression of DDR2/-KD reduced the rate and abundance of collagen deposition and induced significant morphological changes in the resulting fibers. Taken together, our observations extend the functional roles that DDR2 and possibly other membrane-anchored, collagen-binding proteins can play in the regulation of cell adhesion, migration, proliferation and in the remodeling of the extracellular matrix.

Sterols with antileishmanial activity isolated from the roots of Pentalinon andrieuxii.

A new cholesterol derivative, pentalinonsterol (cholest-4,20,24-trien-3-one, 1), and a new polyoxygenated pregnane sterol glycoside, pentalinonside (2), together with 18 known compounds, including 14 sterols (3-16), three coumarins (17-19), and a triterpene (20), were isolated from a n-hexane partition of a methanol extract of the roots of the Mexican medicinal plant Pentalinon andrieuxii. Structure elucidation of compounds 1 and 2 was accomplished by spectroscopic data interpretation. All isolates were evaluated in vitro for their antileishmanial activity. Among these compounds, 6,7-dihydroneridienone (15) was found to be the most potent principle against promastigotes of Leishmania mexicana (L. mexicana). The cholesterol analogue, pentalinonsterol (1), together with two known sterols, 24-methylcholest-4,24(28)-dien-3-one (3) and neridienone (16), also exhibited significant leishmanicidal activity in this same bioassay. Compounds 1, 3, 15, 16, cholest-4-en-3-one (4), and cholest-5,20,24-trien-3β-ol (7), showed strong antileishmanial activity against amastigotes of L. mexicana, and 4 was found to be the most potent agent with an IC(50) value of 0.03μM. All the isolates were also evaluated for their cytotoxicity in non-infected bone marrow-derived macrophages, but none of these compounds was found active towards this cell line. The intracellular parasites treated with compounds 1, 3, 4, 15, and 16 were further studied by electron microscopy; morphological abnormalities and destruction of the amastigotes were observed, as a result of treatment with these compounds.

Ultrastructure as a diagnostic adjunct in the evaluation of lung allograft biopsies.

Humoral immunity contributes significantly to lung graft dysfunction. Recognizing a role of ultrastructural studies in the evaluation and diagnosis of chronic humoral allograft rejection in the kidney, the authors sought to explore its utility as a diagnostic adjunct in lung allograft biopsies. Ultrastructural studies were conducted on 44 biopsies from 26 lung transplant recipients. Endothelial cell activation and necrosis were seen in the setting of acute humoral allograft rejection. Septal chronic vasculopathic changes of thickening and lamellation of the basement membrane zone (BMZ) and BMZ collagen deposition were correlated with greater numbers of humoral allograft rejection episodes and with the development of chronic graft dysfunction/bronchiolitis obliterans syndrome. There was a positive correlation between the extent of septal fibrosis and certain chronic vasculopathic changes, namely collagen deposition in the BMZ and BMZ wrinkling. Patients with chronic graft dysfunction and multiple rejection episodes manifested low diffusion capacities (less than 50% predicted). The results indicate that ultrastructural analysis is useful in identification of septal fibrosis and chronic vasculopathy of the septal microvasculature, correlating with chronic graft dysfunction, encompassing not only fibrotic sequelae of the bronchial wall but also irreversible terminal lung parenchymal changes, the latter associated with repeated episodes of humoral rejection.

Pentalinon andrieuxii root extract is effective in the topical treatment of cutaneous leishmaniasis caused by Leishmania mexicana.

Cutaneous leishmaniasis (CL) manifests as localized skin lesions, which lead to significant tissue destruction and disfigurement. In the Yucatan Peninsula, Mayan traditional healers use Pentalinon andrieuxii Muell.‐Arg. (Apocynaceae) roots for the topical treatment of CL. Here, we studied the effect of P. andrieuxii root hexane extract (PARE) on the parasites and host cells in vitro and examined its efficacy in the topical treatment of CL caused by Leishmania mexicana. PARE exhibited potent antiparasitic activity in vitro against promastigotes as well as amastigotes residing in macrophages. Electron microscopy of PARE‐treated parasites revealed direct membrane damage. PARE also activated nuclear factor kappaB and enhanced interferon‐γ receptor and MHC class II expression and TNF‐α production in macrophages. In addition, PARE induced production of the Th1 promoting cytokine IL‐12 in dendritic cells as well as enhanced expression of the co‐stimulatory molecules CD40, CD80, and CD86. In vivo studies showed that L. mexicana‐infected mice treated by topical application of PARE resulted in the significant reduction in lesion size and parasite burden compared to controls. These findings indicate that PARE could be used as an alternative therapy for the topical treatment of CL. Copyright

Unique pattern of renal κ light chain amyloid deposition with histiocytic transdifferentiation of tubular epithelial cells.

Monoclonal gammopathies can cause renal tubular epithelial damage through multiple mechanisms, the most common manifestation being myeloma cast nephropathy. Amyloid light chain amyloidosis rarely affects the renal tubular epithelium directly and usually causes glomerular injury. Amyloid deposition can also be seen within vessel walls and in the renal tubulointerstitium. Herein, we describe a unique pattern of κ light chain amyloid deposition involving the proximal tubule epithelium in a patient with multiple myeloma, characterized by intracellular amyloid globule formation with concomitant phenotypic changes suggestive of histiocytic differentiation of tubular epithelial cells. Amyloid pathogenesis is thought to be closely associated with the reticuloendothelial system, more specifically macrophages, and histiocytic differentiation of mesangial cells seems to be an integral step in glomerulopathic amyloid production. Our report proposes a similar mechanism of amyloidogenesis in the renal tubular epithelium.

Focal Glomerular Immune Complex Deposition Possible Role of Periglomerular Fibrosis/Atubular Glomeruli

CONTEXT Consensus exists among renal pathologists that, in biopsies with immune complex glomerulonephritis, even a single glomerulus with open capillary loops may be sufficient for immunofluorescence and/or electron microscopy evaluation because immune complex deposition is a diffuse phenomenon. However, we have encountered renal biopsies with focal absence of immune complexes in glomeruli on either immunofluorescence or electron microscopy examination despite presence of open glomerular capillary loops. OBJECTIVE To evaluate renal biopsies with focal immune complex deposition and look for any subtle or unusual morphologic changes in the glomeruli (and in the biopsy in general). DESIGN Native and transplant renal biopsies were reviewed. All biopsies had been triaged and processed according to our routine protocol for light microscopy, immunofluorescence, and electron microscopy examination. RESULTS Of 2018 renal biopsies from December 2005 to December 2007, we found 10 such biopsies; 5 native and 5 transplant kidney biopsies. We found that the glomeruli with absent immune complex deposits had periglomerular fibrosis with open, albeit, wrinkled appearing capillary loops but no glomerular sclerosis. CONCLUSIONS We hypothesize that these histologic features are indicative of nonfunctional glomeruli and may be associated with disconnection between the Bowman capsule and proximal tubule (atubular glomeruli). These glomeruli may not have effective filtration, despite some degree of circulation through the open capillary loops, and therefore are unable to accumulate immune complex deposits. If biopsies are small and only such glomeruli are available for immunofluorescence or electron microscopy examination, the absence of immune complex deposition in them should be evaluated carefully.

Collagen Fibril Ultrastructure in Mice Lacking Discoidin Domain Receptor 1.

The quantity and quality of collagen fibrils in the extracellular matrix (ECM) have a pivotal role in dictating biological processes. Several collagen-binding proteins (CBPs) are known to modulate collagen deposition and fibril diameter. However, limited studies exist on alterations in the fibril ultrastructure by CBPs. In this study, we elucidate how the collagen receptor, discoidin domain receptor 1 (DDR1) regulates the collagen content and ultrastructure in the adventitia of DDR1 knock-out (KO) mice. DDR1 KO mice exhibit increased collagen deposition as observed using Massons trichrome. Collagen ultrastructure was evaluated in situ using transmission electron microscopy, scanning electron microscopy, and atomic force microscopy. Although the mean fibril diameter was not significantly different, DDR1 KO mice had a higher percentage of fibrils with larger diameter compared with their wild-type littermates. No significant differences were observed in the length of D-periods. In addition, collagen fibrils from DDR1 KO mice exhibited a small, but statistically significant, increase in the depth of the fibril D-periods. Consistent with these observations, a reduction in the depth of D-periods was observed in collagen fibrils reconstituted with recombinant DDR1-Fc. Our results elucidate how DDR1 modulates collagen fibril ultrastructure in vivo, which may have important consequences in the functional role(s) of the underlying ECM.