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B K Kishore

Publications and source records attributed to B K Kishore.

At least 37 records · Page 2Linked to original sources
PubMed1994

Increased activities of cathepsin B and other lysosomal hydrolases in fibroblasts and bone tissue cultured in the presence of cysteine proteinases inhibitors.

Leupeptin is an established, reversible inhibitor of cathepsin B, a lysosomal cysteine proteinase. Yet, in rat fibroblasts as well as in foetal mouse calvaria, we observed an increase of the activity of cathepsin B in homogenates of cells and tissue harvested after culture in the presence of leupeptin. This effect was also seen for other lysosomal hydrolases, namely sphingomyelinase, N-acetyl-beta-glucosaminidase, arylsulphatase A and phospholipase A1 in fibroblasts, and beta-glucuronidase in mouse calvaria. In calvaria, antipain, another reversible cysteine proteinase inhibitor, caused a similar effect, whereas E-64, an irreversible inhibitor, was consistently inhibitory of the cathepsin B activity; yet it also caused an increase of beta-glucuronidase activity. The effect of leupeptin in fibroblasts was dose and time-dependent, required the continuous presence of the inhibitor, and was not dependent from protein synthesis. Actually, addition of cycloheximide caused a severe loss of activity of cathepsin B and of sphingomyelinase. In the presence of both cycloheximide and leupeptin, however, these two activities were retained to a value corresponding to that found in excess in cells cultivated with leupeptin alone. The data therefore suggests that leupeptin exerts the effects described in this paper by preventing the degradation of cathepsin B, sphingomyelinase and probably several other lysosomal hydrolases by cysteine proteinases. We therefore propose that cysteine proteinases play a key role in the control of the steady-state levels of these enzymes in normal conditions.

Animals↗
PubMed1994

Leupeptin and E-64, inhibitors of cysteine proteinases, prevent gentamicin-induced lysosomal phospholipidosis in cultured rat fibroblasts.

Aminoglycoside antibiotics, such as gentamicin, cause an early lysosomal phospholipidosis in the renal cortex, which is considered as a key event in the onset of acute tubular necrosis induced by these drugs. In a model of primary cultures of embryonic rat fibroblasts which develop typical lysosomal phospholipidosis when incubated with gentamicin (decrease of sphingomyelinase activity; increase in total cells lipid phosphorus; appearance of so-called 'myeloid bodies' in lysosomes), we observed a protective effect exerted by inhibitors of cysteine proteinases (leupeptin, E-64) against this alteration on the basis of both biochemical and morphological criteria. Actually leupeptin and E-64 caused a marked stimulation of sphingomyelinase activity both in control and in gentamicin-treated cells, which we suggest to be the cause of protection.

Animals↗
PubMed1992

Effect of substrate organization on the activity and on the mechanism of gentamicin-induced inhibition of rat liver lysosomal phospholipase A1.

Aminoglycoside antibiotics, such as gentamicin, induce a lysosomal phospholipidosis in the kidney cortex of experimental animals and humans. In vitro, gentamicin binds to negatively charged phospholipids, such as phosphatidylinositol, and decreases the activity of lysosomal phospholipases towards a neutral phospholipid (phosphatidylcholine) included in lipid vesicles. The mechanism of such an inhibition was not unequivocally established. On one hand Mingeot-Leclercq et al. (Biochem Pharmacol 37: 591-599, 1988) observed that the activity of phospholipase A1 is modulated by the negative charges of the bilayer and that the inhibitory potency of gentamicin is inversely related to the phosphatidylinositol content of the vesicles, and therefore proposed that inhibition is due to charge neutralization. On the other hand, Hostetler and Jellison (J Pharmacol Exp Ther 254: 188-191, 1990) observed that the activity of phospholipase A1 is not modulated by the negative charges of the vesicles and that the inhibitory potency of gentamicin is directly related to the phosphatidylinositol content of the bilayer, and therefore proposed that inhibition is due to substrate depletion. However, the experimental designs of these two models differed in several respects such as the source (liver versus kidney) and nature of the enzyme (native lysosomal extract versus purified delipidated phospholipase A1), and the composition of lipid vesicles (those containing constant amounts of phosphatidylcholine and cholesterol, and inversely varying amounts of phosphatidylinositol and sphingomyelin versus those containing inversely related amounts of phosphatidylcholine and phosphatidylinositol only). In order to assess the nature of the differences between these models, we compared the activity of phospholipase A1 and its inhibition by gentamicin using only one source of enzyme, the rat liver lysosomal extract, and the two types of lipid vesicles as used in the above models. Our results showed that both models are true within the frame work of their respective experimental designs. However, since the composition of the lipid vesicles as well as the nature of the enzyme preparation (whole lysosomal extract) in the "charge neutralization" model is closer to in vivo conditions, we suggest that this model may be more relevant to the in vivo situation.

Animals↗
PubMed1992

Comparative assessment of poly-L-aspartic and poly-L-glutamic acids as protectants against gentamicin-induced renal lysosomal phospholipidosis, phospholipiduria and cell proliferation in rats.

Coadministration of poly-L-aspartic acid (poly-L-Asp) protects rats against all measured signs of aminoglycoside nephrotoxicity. Based on in vitro and acute in vivo models, previously we hypothesized that poly-L-Asp protects by forming complexes with the drug in lysomes of proximal tubular cells. However, another closely related peptide, poly-L-glutamic acid (poly-L-Glu), could not protect against gentamicin-induced phospholipidosis and nephrotoxicity, presumably because it is susceptible to rapid hydrolysis in sysosomes in vivo. The present study expands the in vivo comparison between these two polyanions to a subacute model of rats and examines in detail the influence of these polymers on the qualitative and quantitative morphological alterations of lysosomes, phospholipiduria and proliferation of cortical cells induced by gentamicin. Our results not only demonstrated that despite a significantly higher drug cortical accumulation, the coadministration of poly-L-Asp almost completely protects against the development of all these early renal alteration but also pointed to the possibility of a mild, albeit apparently nonlethal, lysosomal thesaurismosis to develop under these conditions. In contrast, poly-L-Glu could not protect against these early renal alterations, though cortical drug accumulation was not significantly higher; however, it induced a conspicuous proliferation of peritubular interstitial cells. Therefore, the present work, taken together with the earlier results of ours as well as that of others, tends to strengthen the hypothesis that the site of action of poly-L-Asp must be in lysosomes, which are also the organelles that sequester and accumulate the drug.

Animals↗
PubMed1990

Increased levels of protein- and lipid-bound sialic acids in the renal cortex of rats injected with low doses of gentamicin.

Administration of the aminoglycoside antibiotic, gentamicin, even at therapeutic doses, causes renal lysosomal phospholipidosis. We now report that protein- and lipid-bound sialic acid levels are increased significantly in a time-dependent fashion in the renal cortex of rats injected with gentamicin (10 mg/kg body wt. per day) for 4-10 days and a significant relationship could be observed between these two parameters. This elevation was not due to tissue regeneration, since it was not observed in cisplatin-treated animals.

Animals↗
PubMed1990

Inhibition of aminoglycoside-induced nephrotoxicity in rats by polyanionic peptides.

In the present study, we compared poly-L-Asp with poly-L-Glu and poly-D-Glu in vitro and in vivo for their ability to inhibit the GM-induced nephrotoxicity. In vitro, all three polyanions (i) bound GM over a wide range of pH; (ii) displaced GM previously bound to negatively charged phospholipid bilayers at acid pH (i.e. under the conditions prevailing in lysosomes in vivo), and thereby (iii) decreased the inhibitory potency of GM towards lysosomal phospholipase A1. Thus, one was tempted to predict that all three polyanions would have the potential of protecting against AG-induced nephrotoxicity. However, when co-administered to rats with GM, poly-L-Asp and poly-D-Glu completely suppressed the development of lysosomal phospholipidosis, as assessed by biochemical criteria and increased drug accumulation, whereas poly-L-Glu did not offer such protection despite a relatively lower increase in drug accumulation levels. Histoautoradiography also confirmed that poly-L-Asp, but not poly-L-Glu, was a nephroprotectant against the tissue proliferative response induced by GM. Morphologically, poly-L-Asp almost completely and poly-D-Glu totally prevented the accumulation of myeloid bodies in lysosomes. In vitro incubation in the presence of purified lysosomal extracts revealed marked differences in the hydrolysis rate of these peptides (poly-D-Glu:poly-L-Asp:poly-L-Glu = 1:1.2:16.9). Assuming that all three polyanionic peptides are transported and accumulated in lysosomes to the same extent, these results not only suggest that their stability in lysosomes is an essential requisite for protection against lysosomal phospholipidosis, but also strengthen our hypothesis that the site of action of poly-L-Asp is inside the lysosomes but not at the level of the renal membranes. In addition, poly-D-Glu alone or combined with GM induced another type of morphological lesion, not related to AG-induced nephrotoxicity which, to our knowledge, has not yet been described.

Animals↗
PubMed1990

Mechanism of protection afforded by polyaspartic acid against gentamicin-induced phospholipidosis. II. Comparative in vitro and in vivo studies with poly-L-aspartic, poly-L-glutamic and poly-D-glutamic acids.

Poly-L-aspartic acid (poly-L-Asp) protects rats against gentamicin (GM)-induced nephrotoxicity (functional and pathological changes) and early cortical alterations (phospholipidosis and increase in cell turnover) without decreasing, but actually increasing, the renal accumulation of the drug. We suggested that this protection occurs through the complexation of GM by poly-L-Asp, after their pinocytosis and accumulation in the lysosomes of the renal cortex (Kishore et al., J. Pharmacol. Exp. Ther. 867-874, 1990). Here we examine further our proposal by comparatively assessing poly-L-Asp (as provided by the Sigma Chemical Co., St. Louis, MO; MW 9-11,000), with two other polyanionic peptides, viz, poly-L-glutamic (poly-L-Glu; MW 14,300) and poly-D-glutamic (poly-D-Glu; MW 20,000) acids obtained from the same supplier. In vitro, all three polyanions showed a similar capacity to bind GM, to displace it from anionic phospholipids at acid pH and thereby to decrease the inhibitory potency of GM toward lysosomal phospholipase A1. In vivo, however, only poly-L-Asp and poly-D-Glu were able to prevent the development of GM-induced renal lysosomal phospholipidosis as assessed by key biochemical criteria (increase in lipid phosphorus and decrease of acid sphingomyelinase activity) and by examination of the lysosomal content in the electron microscope (accumulation of myeloid bodies). Based on these criteria, poly-L-Glu completely failed to protect. In vitro, poly-L-Glu was 13- to 17-fold more susceptible to hydrolysis by liver lysosomal extracts at pH 5.4 after 48 hr incubation, as compared to poly-L-Asp and poly-D-Glu, respectively. Assuming that all three polyanions tested are transported and accumulated in lysosomes of renal cortex to the same extent and that their respective rates of hydrolysis therein compare to that measured in vitro, these results suggest that stability of polyanions in lysosomes is an essential requisite for protection against GM-induced phospholipidosis and thus strengthens our earlier proposal that the site of action of poly-L-Asp must be in lysosomes. Although protecting from phospholipidosis, poly-D-Glu, however, caused a so far undescribed lysosomal storage disorder consisting of the accumulation of osmiophilic, nonlamellar material. This study, therefore, also demonstrates that not all polyanions resistant to lysosomal enzymes can be used as nephroprotectants, inasmuch as these, as is the case for poly-D-Glu, may cause renal alterations on their own.

Animals↗
PubMed1990

Protection against gentamicin-induced early renal alterations (phospholipidosis and increased DNA synthesis) by coadministration of poly-L-aspartic acid.

Coadministration of polyaspartic acid protects against functional and pathological signs of gentamicin-induced nephrotoxicity in rats without reduction of drug accumulation in renal cortex (Williams et al., J. Pharmacol. Exp. Ther. 237: 919-925, 1986; Gilbert et al., J. Infect. Dis. 159: 945-953, 1989). We have assessed the influence of polyaspartic acid on the early alterations induced in kidney cortex by gentamicin, namely the lysosomal phospholipidosis and the increase in cell turnover. We used an infused rat model in which animals received a total dose of 100 mg/kg of gentamicin over 12 hr. Renal cortex was examined 2 hr (day 0) and 48 hr (day 2) after treatment. All animals received an injection of [3H]thymidine (200 microCi i.p.) before sacrifice. Coadministration of polyaspartic acid (drug-polypeptide mass ratio 1:2.5) did not modify the drug serum levels, as recorded during or shortly after the infusion. Yet, it was associated with 1) an increased (approximately 35%) drug cortical content at day 0; 2) a significant protection against both biochemical (decrease of sphingomyelinase activity at day 0; increase of lipid phosphorus content at day 2) and morphological (enlargement of lysosomes and deposition of myeloid bodies at day 2) signs of lysosomal phospholipidosis in proximal tubular cells; and 3) an almost complete protection against increased cell turnover (mostly in proximal tubules) in cortex at day 2, as assessed by the measurement of [3H]thymidine incorporation into DNA and the enumeration of S-phase cells after histoautoradiography. In addition, morphological studies revealed a larger number of apical vacuoles in proximal tubular cells of animals receiving polyaspartic acid alone (but not in combination with gentamicin), and the deposition of osmiophilic, homogenous material in the lysosomes of animals receiving the combination of gentamicin and polyaspartic acid. Together with the results reported in two companion papers (Kishore et al., J. Pharmacol. Exp. Ther. 867-874, and 875-885, 1990), these results provide evidence that protection afforded by polyaspartic acid extends to the earliest cellular alterations described in kidney for gentamicin, namely the lysosomal phospholipidosis, suggesting that this protecting agent exerts blocking effect from this step in the cascade of events relating drug cortical accumulation to renal toxicity.

Animals↗
PubMed1990

Mechanism of protection afforded by polyaspartic acid against gentamicin-induced phospholipidosis. I. Polyaspartic acid binds gentamicin and displaces it from negatively charged phospholipid layers in vitro.

Coadministration of polyaspartic acid protects rats against aminoglycoside-induced nephrotoxicity, with respect to functional and pathological changes as well as to early signs of renal alterations (lysosomal phospholipidosis of proximal tubular cells, increased proliferation of proximal tubular and peritubular cells), without reduction, but actually by increasing the drug cortical content (Williams et al., J. Pharmacol. Exp. Ther. 237: 919, 1986; Gilbert et al., J. Infect. Dis. 159: 945, 1989; Beauchamp et al., 1990). Because aminoglycoside accumulation in kidney cortex involves their segregation in lysosomes, we have examined the possibility of formation of intracellular aminoglycoside-polyaspartic acid complexes that would render the drug less toxic. We found that in vitro polyaspartic acid (MW 9-15,000) 1) binds gentamicin with an optimum at acidic pH (5.4), 2) displaces it from negatively charged liposomes and 3) restores the activity of gentamicin-inhibited lysosomal phospholipase A1 toward phosphatidylcholine included in negatively charged liposomes. In parallel, we also observed that at pH 7.0, polyaspartic acid binds and displaces gentamicin from purified brush-border membrane vesicles, causing an apparent decrease of affinity of gentamicin for these membranes, which was falsely interpreted by Williams et al., J. Pharmacol. Exp. Ther. 237: 919, 1986 as "competition for a common membrane binding site." Assuming that, after its administration in vivo, polyaspartic acid gains access to lysosomes of proximal tubular cells, as many low molecular weight proteins and polypeptides do, our results suggest that protection against gentamicin-induced nephrotoxicity is obtained by the binding of the aminoglycoside to the polyanion in lysosomes, preventing thereby the development of phospholipidosis and therefore interfering with the cascade of events leading from drug accumulation to nephrotoxicity.

Animals↗
PubMed1989

Clinico-biochemical aspects of guanidine compounds in uraemic toxicity.

"Uraemia" literally means "urine in blood". With the advancement of basic medical sciences, it is being better understood. The clinical syndrome of uraemia is due to the failure of not only the excretory but also the metabolic, regulatory and endocrine functions of the kidney. Apart from the "retained toxic metabolites", a number of guanidine derivatives had been found which are now considered to be more important in the causation of the uraemic syndrome. Cohen had hypothesised that nitrogen retention in uraemia causes an aberration in the urea cycle that in turn leads to the production of guanidinosuccinic acid (GSA) in large amounts. However, it appears that methylguanidine (MG) is produced from the degradation of creatinine by the gut flora in uraemics. Both GSA and MG are proved to be toxic. The role of GSA in uraemic neurotoxicity and coma is still controversial and needs further investigation. It is possible that the combined effects of a number of compounds are responsible for the development of the uraemic syndrome.

Guanidines↗
PubMed1983

Alpha 2HS-glycoprotein in the serum and urine of patients with renal diseases.

The concentration of alpha 2HS-glycoprotein (alpha 2HS-GP), as measured by the single radial immunodiffusion technique in the sera of 52 patients with various renal diseases and varying degrees of proteinuria, was found to be significantly reduced (P less than 0.001) when compared to the control values. Out of the 52 patients examined, 34 were found to excrete alpha 2HS-GP in urine with no correlation between the serum and urine levels of this protein. Although there is a statistically significant correlation between the clearances of albumin and alpha 2HS-GP, in only six patients were the clearances of alpha 2HS-GP within +/- 25% of albumin clearance. Twelve had higher, and 16 had lower, relative clearances of alpha 2HS-GP. The relative clearance of alpha 2HS-GP had no relation to the serum levels of alpha 2HS-GP, but correlated with the degree of proteinuria and the type of histological lesion in the kidney. In conclusion, there is a quantitative reduction of serum alpha 2HS-GP in patients with renal diseases. It appears that the degree of proteinuria and the type of renal lesion influences its selective handling by the kidneys.

Blood Proteins↗
PubMed1983

Altered glycosylation and sialylation of serum proteins and lipid bound sialic acids in chronic renal failure.

Abnormalities in the metabolism of carbohydrates, lipids and proteins are well documented in chronic renal failure (CRF). We have studied the extent of glycosylation and sialylation of serum proteins and also the levels of lipid-bound sialic acids in nondiabetic patients with CRF maintained on haemodialysis. The total neutral sugar content (TNS) and the non-enzymatic glycosylation (NEG) of serum proteins, the protein-bound sialic acids (PSA) and the lipid-bound sialic acids (LSA) were found to be significantly elevated in the patients as compared to a group of healthy controls. A single dialysis therapy produced some alterations in these measurements. The TNS correlated significantly with the NEG and also with the PSA. No correlation existed between total lipids. None of these measurements, however, correlated with the serum creatinine values. The established as well as putative pathophysiological consequences of these findings are discussed.

Blood Proteins↗
PubMed1983

Prolidase and prolinase activities in the erythrocytes of patients with chronic uremia.

To elucidate the nature of the iminoacidopathy in uremia, the prolidase and prolinase activities in erythrocytes from 36 normal subjects, 28 patients with chronic uremia, and 21 patients on maintenance hemodialysis were determined. A statistically significant decrease in the activities of both prolidase and prolinase was found in the uremic patients and the hemodialysis group. No difference has been observed in the enzyme activities in the pre- and postdialysis samples of the hemodialysis patients. It is suggested that decreased activities of prolidase and prolinase may contribute to the iminoacidopathy in uremia, including high contents of serum iminoacid containing peptides.

Adult↗