Distribution of anticancer antibiotic daunomycin in the rat heart and kidney revealed by immunocytochemistry using monoclonal antibodies

Two monoclonal antibodies (ADM-1-11 and 79-31 mAbs) were raised against daunomycin (DM) conjugated to bovine serum albumin via the cross-linker N-(gamma-maleimidobutyryloxy)succinimide. The monoclonal antibodies (mAbs) specifically detected DM as well as its analogs doxorubicin and epirubicin, but did not react with other anticancer antibiotics, including pepleomycin, mitomycin C, and actinomycin D. The mAbs reacted strongly with glutaraldehyde-conjugated DM in an enzyme linked immunosorbent assay (ELISA) used as a model system for immunocytochemistry as well as in appropriately pretreated sections of tissues from animals injected with DM. No staining occurred in tissues from uninjected animals. In order to perform DM ICC a number of tissue treatment conditions critical to the detection of low molecular weight substances were employed. Uptake of DM was studied in rats after a single i.v. or i.p. administration of the drug. In the heart, accumulation of DM occurred in nuclei and in the cytoplasm. In the kidney, DM immunoreactivity accumulated in all segments of the nephron except for the proximal tubules. Since the proximal tubules are known to be where a variety of transport systems including P-glycoprotein (Pgp) and organic anion-transporting polypeptides (OATPs) in drug interactions occur, the absence of DM accumulation in these segments may reflect a transport phenomenon depending upon such transporters. The availability of methods to study sites of accumulation of DM offers possibilities for understanding toxic side effects of this drug on the heart and kidney. Moreover, the immunocytochemical methodology developed may prove useful for the localization of other low molecular weight drugs that can be fixed in situ by glutaraldehyde.     

Improved immunocytochemical detection of daunomycin

Improved immunocytochemical (ICC) detection of the anthracycline anticancer antibiotic daunomycin (DM) has been achieved by use of hydrogen peroxide oxidation prior to ICC staining for DM. The new method greatly enhanced the localization of DM accumulation in cardiac, smooth and skeletal muscle of rats after a single i.v. dose of the drug. DM accumulated in the nuclei as well as in the sarcoplasm, where it occurred in the form of small granules, which were particularly evident in cardiac muscle cells. The distribution of the granules coincided with that of mitochondria. Uptake of DM in nuclei and mitochondria of heart muscle cells may help to improve our understanding of the cardiac toxicity of DM and related anthracyclin antibiotics. A number of ELISA tests were carried out in order to elucidate the mechanims of H₂O₂−assisted antigen retrieval. A possible mechanism is that DM is reduced and converted to its semiquinone and/or hydroquinone derivative in vivo. Oxidation by hydrogen peroxide acts to convert these derivatives back to the native antigen. The improved ICC methodology using oxidation to recreate native antigens from reduced metabolites may be helpful also with respect to the localization of other drugs.     

A probable relationship between characteristic accumulation of doxorubicin and P-glycoprotein transporter in rat liver

Correlations between the distribution of anthracycline antibiotics doxorubicin (DX) and daunorubicin (DR) in the liver of rats injected with a single i.v. injection of each drug and the reported distribution of P-glycoprotein transporter for the drug was histochemically examined. Immunocytochemical studies for DX or DR using monoclonal antibody that equally detects both drugs, as well as conventional electron microscopy were employed. DX persisted for more than 5 days in the cytoplasm and nuclei of the hepatocytes in a characteristic granular morphology on the bile capillaries. Meanwhile, DR distributed in almost the same pattern, but more rapidly decreased to a level that almost no granular morphology in the hepatocytes was visible 24 h after the injection. Also, unknown large cells that strongly reacted with the antibody appeared in the hepatic sinusoids near the interlobular triads rather than the central vein. The accumulation sites of DX or DR on the bile capillaries seems to correspond to specific sites where the ATP-binding cassette transport protein P-glycoprotein for the anthracycline occurs, suggesting a possibility that DX or DR is actually and actively excreted at these sites, possibly through P-glycoprotein. This is supported by conventional electron microscopic studies, since no specific subcellular organelles such as lysosomes assemble in the vicinity of the bile capillaries of the hepatocytes.     

Rab GTPases regulating phagosome maturation are differentially recruited to mycobacterial phagosomes

Mycobacterium tuberculosis (M. tb) is an intracellular pathogen that can replicate within infected macrophages. The ability of M. tb to arrest phagosome maturation is believed to facilitate its intracellular multiplication. Rab GTPases regulate membrane trafficking, but details of how Rab GTPases regulate phagosome maturation and how M. tb modulates their localization during inhibiting phagolysosome biogenesis remain elusive. We compared the localization of 42 distinct Rab GTPases to phagosomes containing either Staphylococcus aureus or M. tb. The phagosomes containing S. aureus were associated with 22 Rab GTPases, but only 5 of these showed similar localization kinetics as the phagosomes containing M. tb. The Rab GTPases responsible for phagosome maturation, phagosomal acidification and recruitment of cathepsin D were examined in macrophages expressing the dominant-negative form of each Rab GTPase. LysoTracker staining and immunofluorescence microscopy revealed that Rab7, Rab20 and Rab39 regulated phagosomal acidification and Rab7, Rab20, Rab22b, Rab32, Rab34, Rab38 and Rab43 controlled the recruitment of cathepsin D to the phagosome. These results suggest that phagosome maturation is achieved by a series of interactions between Rab GTPases and phagosomes and that differential recruitment of these Rab GTPases, except for Rab22b and Rab43, to M. tb-containing phagosomes is involved in arresting phagosome maturation and inhibiting phagolysosome biogenesis.     

Sub-zero temperature inactivation of carboxypeptidase Y under high hydrostatic pressure.

High hydrostatic pressure induced cold inactivation of carboxypeptidase Y. Carboxypeptidase Y was fully active when exposed to subzero temperature at 0.1 MPa; however, the enzyme became inactive when high hydrostatic pressure and subzero temperature were both applied. When the enzyme was treated at pressures higher than 300 MPa and temperatures lower than -5 degrees C, it underwent an irreversible inactivation in which nearly 50% of the alpha-helical structure was lost as judged by circular dichroism spectral analysis. When the applied pressure was limited to below 200 MPa, the cold inactivation process appeared to be reversible. In the presence of reducing agent, this reversible phenomenon, observed at below 200 MPa, diminished to give an inactive enzyme; the agent reduces some of disulfide bridge(s) in an area of the structure that is newly exposed area because of the cold inactivation. Such an area is unavailable if carboxypeptidase Y is in its native conformation. Because all the disulfide bridges in carboxypeptidase Y locate near the active site cleft, it is suggested that the structural destruction, if any, occurs preferentially in this disulfide rich area. A possible mechanism of pressure-dependent cold inactivation of CPY is to destroy the alpha-helix rich region, which creates an hydrophobic environment. This destruction is probably a result of the reallocation of water molecules. Experiments carried out in the presence of denaturing agents (SDS, urea, GdnHCl), salts, glycerol, and sucrose led to a conclusion consistent with the idea of water reallocation.