Natural killer cell-mediated lysis of herpes simplex virus-infected fibroblasts: inability to detect soluble factors that contribute to lysis

We investigated the role of soluble factors in natural killer (NK) cell-mediated lysis of herpes simplex virus (HSV)-infected cells. Supernatants generated by incubating human peripheral blood mononuclear cells with HSV-infected human fibroblasts contained tumor necrosis factor (TNF) and lysed uninfected U937 cells, but not HSV-infected fibroblasts. U937 cells, but not HSV-infected fibroblasts, were lysed when exposed to recombinant TNF (rTNF) for 18 hr. NK cell-mediated lysis of HSV-infected fibroblasts was not inhibited by addition of anti-TNF or anti-lymphotoxin (LT) antibodies to cytotoxicity assays. Thus, a role for soluble factors, and in particular TNF and LT, in NK cell-mediated lysis of HSV-infected cells could not be demonstrated.

Natural killer cell-mediated lysis of T cell lines chronically infected with HIV-1

The susceptibility of HIV-1-infected CD4+ T cell lines to natural killer (NK) cell-mediated lysis was examined. Non-adherent peripheral blood mononuclear cells (PBMC) of healthy adults lysed HUT cells chronically infected with the IIIB or WMJ1 strains of HIV-1 to a significantly greater extent than uninfected HUT cells. In contrast, Sup-T1 cells chronically infected with these two strains of HIV-1 were not lysed to a greater extent than uninfected Sup-T1 cells. Clone A1.25-infected Sup-T1 (A1.25/Sup-T1), derived from IIIB-infected Sup-T1 cells (IIIB/Sup-T1), were susceptible to non-adherent PBMC-mediated lysis, as were A1.25-infected HUT cells (A1.25/HUT). When non-adherent PBMC were depleted of CD16 (Leu-11b)+ NK cells by treatment with anti-Leu-11b plus C, lysis of HIV-1-infected HUT or Sup-T1 cells was reduced to low levels, indicating that the lysis was mediated by NK cells. Expression of HIV antigens on these target cells did not correlate with their susceptibility to NK cell-mediated lysis. Depletion of interferon-alpha (IFN-alpha) producing HLA-DR+ cells from non-adherent PBMC had no effect on the magnitude of NK cell-mediated lysis of IIIB or WMJ1-infected HUT cells. In contrast, lysis of A1.25/Sup-T1 or A1.25/HUT cells required the presence of HLA-DR+ cells. IFN-alpha production appeared to be required for NK cell-mediated lysis of A1.25/Sup-T1 or A1.25/HUT cells, while lysis of HUT cells infected with the WMJ1 or IIIB strains of HIV-1 was IFN-alpha independent. These results indicate considerable variability in the susceptibility of different HIV-1 infected T cell lines to NK cell-mediated lysis and suggest the existence of alternative mechanisms of activation of NK cells for lysis of HIV-1-infected T cell lines.

Amiodarone- and desethylamiodarone-induced myelinoid inclusion bodies and toxicity in cultured rat hepatocytes

Hepatocytes isolated from Sprague-Dawley rats were incubated with various concentrations of either amiodarone or desethylamiodarone for 0 to 96 hr. Both drugs produced a concentration-dependent increase of lactate dehydrogenase release in the culture medium, which correlated well with cell death as measured by trypan blue exclusion test. Desethylamiodarone was more toxic than amiodarone in the cultured hepatocytes. Incubation with subtoxic concentrations of either amiodarone (7.6 microM) or desethylamiodarone (8 microM) for 24 hr resulted in the development of myelinoid inclusion bodies in the hepatocytes without any excess release of lactate dehydrogenase. In experimental protocols where the hepatocytes were exposed to either amiodarone or desethylamiodarone for up to 96 hr, there was an increase in lactate dehydrogenase and the percent volume-density of multilamellar inclusion bodies with cumulative drug exposure with time. A linear correlation between hepatocyte drug concentration and multilamellar inclusion bodies was found for both amiodarone and desethylamiodarone. These results demonstrate that both amiodarone and its major metabolite, desethylamiodarone, induce lysosomal inclusions, which, under appropriate conditions, can be dissociated from cell death. Withdrawal of the drug after 24 hr exposure did not result in disappearance of the inclusion bodies from the hepatocytes for up to 96 hr of tissue culture. The concentrations at which amiodarone- or desethylamiodarone-induced electron microscopic changes and hepatotoxicity were only two to five times as high as the usual serum drug levels in patients given antiarrhythmic therapy with amiodarone.

Subcellular changes of rat myocardium after treatment with amiodarone or desethylamiodarone, studied with electron microscopy

Amiodarone, an antiarrhythmic agent, has proven to be unique in its capability to control arrhythmias unresponsive to conventional drugs. However, its association with many undesirable side effects after chronic usage has become just as clear. Chronic clinical toxicity with amiodarone is associated with intracellular lamellar or myelinoid inclusion bodies (onionoid bodies or corpora cepiformia) in various organs (i.e. skin, cornea, lung, liver, and lymph nodes). Previous study has demonstrated formation of these inclusion bodies in canine myocardium following multiple doses of amiodarone. The present study was designed to develop a more convenient animal model, and to measure the concentration of amiodarone, as well as desethylamiodarone (its major metabolite) in this rodent model. The direct role of desethylamiodarone in formation of lamellar inclusion bodies in rat myocardium was also investigated. Amiodarone (50 mg/kg) or desethylamiodarone (25 mg/kg) was injected intraperitoneally daily for a period of 14 days. Myocardial sections revealed the presence of lamellar inclusion bodies, round or oval in appearance, in the form of laminated or concentrically arranged membranes after either amiodarone or desethylamiodarone treatment. This is the first reference to the induction of these myelinoid inclusion bodies with desethylamiodarone. Myocardial tissue concentrations of amiodarone and desethylamiodarone exceeding plasma concentrations were found in the present study and indicate the capability of these compounds to easily distribute and accumulate in the myocardium.

Dendritic cells and IFN-alpha-producing cells are two functionally distinct non-B, non-monocytic HLA-DR+ cell subsets in human peripheral blood

At least two distinct HLA-DR+ cell subsets lacking surface markers specific for B cells, monocytes or other known lineages are present in human peripheral blood. One subset is non-adherent to plastic, produces interferon-alpha (IFN-alpha) when incubated with cytomegalovirus-infected target cells and provides an accessory function required for natural killer (NK) cell-mediated lysis of such cells. These non-adherent HLA-DR+ cells express the surface antigen recognized by antibody anti-D44 and do not stimulate mixed leucocyte reaction (MLR). The other HLA-DR+ cell subset is loosely adherent to plastic, produces only minimal levels of IFN-alpha when incubated with cytomegalovirus-infected target cells and does not provide the accessory function required for NK cell-mediated lysis of such cells. These HLA-DR+ cells stimulate a strong MLR, do not express D44 antigen and meet the criteria of dendritic cells (DC) morphologically and functionally.

Repression of sporulation: isolation and characterization of repression-resistant mutants of Bacillus subtilis

The sporulation of Bacillus subtilis B34 was repressed by 24 h if glutamine or ammonium chloride but not glutamate was added at late log phase (70 h) when glucose and glutamate were nearly exhausted. Glutamine-resistant mutants were isolated by selective heat treatment during the delay period induced by glutamine. Glutamine-resistant mutants showed cross resistance not only against ammonium chloride but also against glucose just as glucose-resistant mutants showed resistance against nitrogenous catabolites.

Contractile force and intracellular Ca2+ during relaxation of canine tracheal smooth muscle

Muscle strips loaded with the Ca2+ indicator aequorin were studied in vitro to determine the effects of inhibitory stimuli on force and cytosolic free Ca2+. In muscles contracted isometrically with acetylcholine (ACh), 5-hydroxytryptamine (5-HT), carbachol, decreases in muscle force caused by isoproterenol (10(-5) M) or forskolin (10(-5) M) were accompanied by proportional decreases in aequorin luminescence. A similar relationship between decreases in muscle force and aequorin luminescence was observed when muscles were relaxed by stimulating Na+-K+-ATPase activity. These results suggest that the Ca2+ sensitivity of contractile proteins was not decreased during adenosine 3',5'-cyclic monophosphate (cAMP)-dependent relaxation. However, aequorin luminescence did not decrease when muscles contracted by K+ depolarization were relaxed with isoproterenol. Incubation of muscles in forskolin depressed increases in both force and aequorin luminescence in response to 5-HT or ACh. Incubation of muscles in isoproterenol had a similar effect on responses to 5-HT but depressed increases in force without depressing increases in luminescence in response to ACh. Results indicate that under most conditions the reduction of cytosolic Ca2+ plays an important role in the cAMP-dependent relaxation of canine tracheal smooth muscle.

TGF beta inhibits Go/S-phase transition in primary fibroblasts. Loss of response to the antigrowth effect of TGF beta is observed after immortalization

Transforming growth factor beta (TGF beta) may act as a negative growth regulator in secondary cultures of rodent fibroblasts by preventing quiescent cells from re-entering the cell cycle. Although TGF beta inhibits the serum induced transition from the Go to the S phase it does not inhibit induction of fos, myc, and JE. Actively growing cells are also inhibited in their proliferation by picomolar amounts of TGF beta. In contrast several established cell lines are not inhibited by TGF beta and in these it can cause quiescent cells to resume proliferation. This resistance to TGF beta can be traced back to the early divisions of immortal cells emerging from a senescence crisis, suggesting that alterations in the response of normal fibroblasts to TGF beta are concurrent with an unlimited proliferative potential. Induction of DNA synthesis by TGF beta is preceded in 5 established cell lines by induction of PDGF B chain mRNA as well as of other mRNAs associated with cell replication such as fos, myc, and JE. None of these genes is induced by TGF beta alone in presenescent cells. These results indicate that TGF beta can negatively regulate growth of normal presenescent fibroblasts. Alterations in the responsiveness to TGF beta can be detected immediately after immortalization which may contribute to the increased proliferative potential of these cells.

Amiodarone and desethylamiodarone toxicity in isolated hepatocytes in culture

Amiodarone, a class III antiarrhythmic drug, has been found to be effective in the management of patients with life-threatening ventricular arrhythmias. Recent reports describe the presence of myelinoid inclusion bodies following amiodarone therapy in liver, myocardium, white blood cells, lung, cornea, skin, and lymph nodes; their relationship to toxicity is unclear. The exact role of desethylamiodarone, the major metabolite, of amiodarone in systemic toxicity of the parent drug is not known. Concentration-response relationships for amiodarone and desethylamiodarone were investigated by adding 1-50 micrograms/ml of the compounds of dimethyl sulfoxide (controls) to hepatocytes isolated from Sprague-Dawley rats and cultured in Leibovitz L-15 medium. Using lactate dehydrogenase release into the medium to quantitate cell death, both drugs were found to cause cell death in a concentration-dependent manner within 24 hr of incubation; this data showed desethylamiodarone to be significantly more toxic than amiodarone. In experiments with 50-micrograms/ml concentrations of amiodarone or desethylamiodarone, we found desethylamiodarone to produce a significantly greater release of lactate dehydrogenase as compared with amiodarone within 2-4 hr. Electron microscopic studies indicated the presence of myelinoid inclusion bodies at early culture stages followed by progressive swelling of mitochondria and rough endoplasmic reticula, disruption of membranes, aggregation of subcellular structures, and ultimately cell death. Ultrastructural changes occurred sooner in the hepatocytes treated with desethylamiodarone than with amiodarone. These data demonstrate that (i) desethylamiodarone is more toxic than amiodarone; (ii) acute toxicity of desethylamiodarone and amiodarone can be quantitated by lactate dehydrogenase release; (iii) both desethylamiodarone and amiodarone can induce myelinoid inclusion bodies in cultured hepatocytes; and (iv) toxicity is characterized by progressive subcellular changes leading to cell death.

Natural killing of fibroblasts infected with low-passage clinical isolates of human cytomegalovirus

Fibroblasts infected with most low-passage clinical isolates of human cytomegalovirus (CMV) were as susceptible to lysis by human natural killer (NK) cells as high passage AD-169-infected fibroblasts. NK lysis occurred despite the absence of detectable CMV-specific late membrane antigen(s) on the majority of the target cells infected with most of the low passage strains. The magnitude of NK lysis of different CMV-infected target cells did not correlate with their ability to induce IFN-alpha. NK cell-mediated lysis of cells infected with low-passage clinical isolates of CMV required both NK cells and HLA-DR+ accessory cells, as previously shown for AD-169-infected target cells.

Unexpected binding of an octapeptide to the angiotensin II receptor

An octapeptide, TBI-22 (Lys-Gly-Val-Tyr-Ile-His-Ala-Leu), inhibited binding of angiotensin II by a solubilized angiotensin receptor partially purified from rabbit liver. This inhibition appears to result from competition for binding to the same receptor. Radioiodinated TBI-22, like angiotensin II, bound to the solubilized receptor with an affinity such that the binding was inhibited 50% by unlabeled TBI-22 or angiotensin II at nanomolar concentrations. The binding reaction, like that for angiotensin II, required p-chloromercuriphenylsulfonic acid and was reversed in the presence of dithiothreitol. TBI-22 and angiotensin II share the sequence Val-Tyr-Ile-His; this tetrapeptide alone, however, did not inhibit binding of angiotensin II. Replacement of the tyrosine residue by aspartic acid in TBI-22 greatly reduced the ability of the peptide to compete with angiotensin II for binding, suggesting an important contribution of this residue to the configuration required for recognition by the receptor.

Cooperation between CD16(Leu-11b)+ NK cells and HLA-DR+ cells in natural killing of herpesvirus-infected fibroblasts

We reported previously that natural killer (NK) cell-mediated lysis of cytomegalovirus-infected targets requires the presence of HLA-DR+ nonadherent peripheral blood mononuclear cells (NPBMC). In the present study we determined whether NK cell-mediated lysis of other herpesvirus-infected targets also requires HLA-DR+ cells. Depletion of either cluster designation (CD)16+ NK cells or HLA-DR+ cells from NPBMC significantly reduced their ability to lyse herpes simplex virus (HSV)- and varicella-zoster virus (VZV)-infected fibroblasts. When CD16- and HLA-DR- populations were mixed, lysis of both HSV- and VZV-infected targets was virtually completely restored, indicating that NK cells and HLA-DR+ cells were required for lysis to occur. Cell-free supernatants, obtained by incubating NPBMC or CD16- cells with HSV-o-VZV-infected targets, contained antiviral activity and stimulated HLA-DR-cells to mediate lysis of corresponding virus-infected targets. The addition of anti-interferon-alpha to supernatants abolished their ability to stimulate lysis. Thus, secretion of interferon-alpha by HLA-DR+ cells contributes to NK cell-mediated lysis of herpesvirus-infected targets.

Cooperation between CD16(Leu-11b)+ NK cells and HLA-DR+ cells in natural killing of herpesvirus-infected fibroblasts

We reported previously that natural killer (NK) cell-mediated lysis of cytomegalovirus-infected targets requires the presence of HLA-DR+ nonadherent peripheral blood mononuclear cells (NPBMC). In the present study we determined whether NK cell-mediated lysis of other herpesvirus-infected targets also requires HLA-DR+ cells. Depletion of either cluster designation (CD)16+ NK cells or HLA-DR+ cells from NPBMC significantly reduced their ability to lyse herpes simplex virus (HSV)- and varicella-zoster virus (VZV)-infected fibroblasts. When CD16- and HLA-DR- populations were mixed, lysis of both HSV- and VZV-infected targets was virtually completely restored, indicating that NK cells and HLA-DR+ cells were required for lysis to occur. Cell-free supernatants, obtained by incubating NPBMC or CD16- cells with HSV-o-VZV-infected targets, contained antiviral activity and stimulated HLA-DR-cells to mediate lysis of corresponding virus-infected targets. The addition of anti-interferon-alpha to supernatants abolished their ability to stimulate lysis. Thus, secretion of interferon-alpha by HLA-DR+ cells contributes to NK cell-mediated lysis of herpesvirus-infected targets.

A comparison of plasma, white blood cell, red blood cell, and tissue distribution of amiodarone and desethylamiodarone in anesthetized dogs

Desethylamiodarone (DA) is a major metabolite of amiodarone (AM), a Class III antiarrhythmic drug. The plasma pharmacokinetics and tissue distribution of AM and DA (10 mg/kg i.v.) were compared in anesthetized dogs. Plasma, white blood cell (WBC), red blood cell (RBC), liver, and skeletal muscle samples were obtained at frequent intervals up to 6 h after a single i.v. bolus of the two drugs. Drug concentrations in these and other tissues, i.e., lung, kidney, heart (right and left atrium, right and left ventricle, Purkinje fibers, and AV node), and femoral nerve were measured by a highly sensitive and specific high-pressure liquid chromatographic technique developed in our laboratory. Four different patterns of AM and DA uptake and washout could be identified in these experiments. The first pattern is biexponential decline in plasma drug levels with a rapid distribution phase (t1/2 alpha = 5.1 +/- 2.1 min for AM and 5.5 +/- 1.2 min for DA, respectively) and a slower elimination phase (t1/2 beta = 3.7 +/- 1.3 h for AM and 4.96 +/- 0.8 h for DA, respectively). The volume of distribution of DA was significantly larger than that of AM. The second pattern is that both WBCs and RBCs showed an initial uptake within 5 min followed by a biexponential decrease in drug levels, with t1/2 alpha similar to that in plasma but t1/2 beta significantly longer than in plasma. In both these types of cells, the elimination half-life for DA was significantly longer than that of AM. The third pattern is that in the liver there was a rapid uptake of both drugs with peak concentrations at 15 min; the decline in hepatic levels of AM was biexponential, but that of DA appeared to be monoexponential. In addition, in dogs given AM alone, the metabolite (DA) was easily detected in the liver from the earliest time of measurement, suggesting that the parent drug is rapidly metabolized to DA. In the experiments where DA was injected, two new peaks were also identified in the liver suggesting that DA was metabolized further in the liver. The fourth pattern was in the skeletal muscle, where AM uptake was relatively slow, reaching peak concentrations between 1.5-2 h followed by a monoexponential decline; however, DA was rapidly taken up by skeletal muscle, but the rate of decline appeared to be slower as compared to that of AM.(ABSTRACT TRUNCATED AT 400 WORDS)

Amiodarone and multilamellar inclusion bodies

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The plantar nerves-lumbrical muscles: a useful nerve-muscle preparation for assaying the effects of botulinum neurotoxin

The plantar nerves-lumbrical muscles (PL) of the hindpaw of the mouse is a preparation that is particularly useful for assaying the effects of botulinum neurotoxin (NT) on the mammalian neuromuscular junction. Each mouse provides a minimum of 4 and a maximum of 8 such preparations. The muscles are thin enough so that neuromuscular junctions can be easily located with Nomarski interference contrast optics for impaling with microelectrodes. The preparations are small enough so they can be sectioned transversely or longitudinally, in their entirety, for light and electron microscopy, or just the regions containing end-plates can be used. An examination of the responses of this preparation to types A and E NT reveal its exceptional suitability for experiments with NT. The small number of fibers and their arrangement permit assays of low concentrations of NT to proceed to complete and total paralysis in a convenient period of time.

Role of the heavy and light chains of botulinum neurotoxin in neuromuscular paralysis

Botulinum neurotoxin (NT) is synthesized by Clostridium botulinum in any of seven antigenically distinct forms called types A-G. NT, when fully active, is a dichain protein, composed of two polypeptides, a heavy (H) and a light (L) chain (approximately 100,000 and approximately 50,000 Da, respectively) that are held together by noncovalent bonds and at least one disulfide bond. Two types of dichain NT, A and B, and their respective H and L chains were applied to nerve-muscle (NM) preparations (phrenic nerve-hemidiaphragm of the mouse), in order to develop a broader, comparative understanding of the neuroparalytic actions of NT types. It was found that the paralysis induced by dichain NT was delayed or antagonized if NM preparations were incubated with isolated and purified H chain prior to, or during, incubation with the parent, dichain NT. NM preparations preincubated with H chain and then washed free of unbound H chain became paralyzed after subsequent incubation with L chain. Paralysis did not occur if NM preparations were incubated first with L chain, washed, and then incubated with H chain. These observations suggest that the H chain binds with specific sites on the nerve terminal. This binding appears to permit the L chain, or some combination of the L and H chain, to bring about neuroparalysis through a mechanism very similar to that of the parent, dichain NT.