Induction of apoptosis in HL-60 cells by lithium

Targeting CaN/NFAT in Alzheimer's brain degeneration

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by a progressive loss of cognitive functions. While the exact causes of this debilitating disorder remain elusive, numerous investigations have characterized its two core pathologies: the presence of β-amyloid plaques and tau tangles. Additionally, multiple studies of postmortem brain tissue, as well as results from AD preclinical models, have consistently demonstrated the presence of a sustained inflammatory response. As the persistent immune response is associated with neurodegeneration, it became clear that it may also exacerbate other AD pathologies, providing a link between the initial deposition of β-amyloid plaques and the later development of neurofibrillary tangles. Initially discovered in T cells, the nuclear factor of activated T-cells (NFAT) is one of the main transcription factors driving the expression of inflammatory genes and thus regulating immune responses. NFAT-dependent production of inflammatory mediators is controlled by Ca2+-dependent protein phosphatase calcineurin (CaN), which dephosphorylates NFAT and promotes its transcriptional activity. A substantial body of evidence has demonstrated that aberrant CaN/NFAT signaling is linked to several pathologies observed in AD, including neuronal apoptosis, synaptic deficits, and glia activation. In view of this, the role of NFAT isoforms in AD has been linked to disease progression at different stages, some of which are paralleled to diminished cognitive status. The use of classical inhibitors of CaN/NFAT signaling, such as tacrolimus or cyclosporine, or adeno-associated viruses to specifically inhibit astrocytic NFAT activation, has alleviated some symptoms of AD by diminishing β-amyloid neurotoxicity and neuroinflammation. In this article, we discuss the recent findings related to the contribution of CaN/NFAT signaling to the progression of AD and highlight the possible benefits of targeting this pathway in AD treatment.

Niclosamide modulates cyclosporin A-induced hepatotoxicity in a mouse model: PPAR-γ and Wnt/β-catenin crosstalk

OBJECTIVES

The aim of this study was to evaluate whether: 1) Wnt/β-catenin signaling is involved in cyclosporin A (CsA)-induced hepatotoxicity, and 2) knockdown of this pathway by niclosamide (NCL) attenuate CsA-induced hepatotoxicity.

METHODS

The experiment was accomplished in 21 days. Adult male mice were randomly distributed into five groups: control group, CsA (25 mg/kg/day) group, CsA + NCL (2.5 mg/kg/day) group, CsA + NCL (5 mg/kg/day) group, and NCL (5 mg/kg/day) group.

RESULTS

NCL showed marked hepatoprotection by significantly decreasing liver enzymes activities and ameliorating the histopathological alterations induced by CsA. Besides, NCL alleviated oxidative stress and inflammation. NCL-treated groups (2.5 and 5 mg/kg) displayed rise in the expression of hepatic peroxisome proliferator-activated receptor-γ (PPAR-γ) by 2.1- and 2.5-fold, respectively. Notably, NCL (2.5 and 5 mg/kg) significantly inhibited Wnt/β-catenin signaling, evidenced by a marked decrease in the hepatic expression of Wnt3a by 54 % and 50 %, frizzled-7 receptor by 50 % and 50 %, β-catenin by 22 % and 49 %, and c-myc by 50 % and 50 %, respectively.

CONCLUSIONS

NCL can be regarded as a potential agent to mitigate CsA-induced hepatotoxicity.

Cationic Substitutions in Hydroxyapatite: Current Status of the Derived Biofunctional Effects and Their In Vitro Interrogation Methods

High-performance bioceramics are required for preventing failure and prolonging the life-time of bone grafting scaffolds and osseous implants. The proper identification and development of materials with extended functionalities addressing socio-economic needs and health problems constitute important and critical steps at the heart of clinical research. Recent findings in the realm of ion-substituted hydroxyapatite (HA) could pave the road towards significant developments in biomedicine, with an emphasis on a new generation of orthopaedic and dentistry applications, since such bioceramics are able to mimic the structural, compositional and mechanical properties of the bone mineral phase. In fact, the fascinating ability of the HA crystalline lattice to allow for the substitution of calcium ions with a plethora of cationic species has been widely explored in the recent period, with consequent modifications of its physical and chemical features, as well as its functional mechanical and in vitro and in vivo biological performance. A comprehensive inventory of the progresses achieved so far is both opportune and of paramount importance, in order to not only gather and summarize information, but to also allow fellow researchers to compare with ease and filter the best solutions for the cation substitution of HA-based materials and enable the development of multi-functional biomedical designs. The review surveys preparation and synthesis methods, pinpoints all the explored cation dopants, and discloses the full application range of substituted HA. Special attention is dedicated to the antimicrobial efficiency spectrum and cytotoxic trade-off concentration values for various cell lines, highlighting new prophylactic routes for the prevention of implant failure. Importantly, the current in vitro biological tests (widely employed to unveil the biological performance of HA-based materials), and their ability to mimic the in vivo biological interactions, are also critically assessed. Future perspectives are discussed, and a series of recommendations are underlined.

Biphasic dose-dependent effect of lithium chloride on survival of human hormone-dependent breast cancer cells (MCF-7)

Lithium, the first element of Group I in the periodic system, is used to treat bipolar psychiatric disorders. Lithium chloride (LiCl) is a selective inhibitor of glycogen synthase kinase-3β (GSK-3β), a serine/threonine kinase that regulates many cellular processes, in addition to its role in the regulation of glycogen synthase. GSK-3β is emerged as a promising drug target for various neurological diseases, type-2 diabetes, cancer, and inflammation. Several works have demonstrated that lithium can either inhibit or stimulate growth of normal and cancer cells. Hence, the present study is focused to analyze the underlying mechanisms that dictate the biphasic oncogenic properties of LiCl. In the current study, we have investigated the dose-dependent effects of LiCl on human breast cancer cells (MCF-7) by assessing the consequences on cytotoxicity and protein expressions of signaling molecules crucial for the maintenance of cell survival. The results showed breast cancer cells respond in a diverse manner to LiCl, i.e., at lower concentrations (1, 5, and 10 mM), LiCl induces cell survival by inhibiting apoptosis through regulation of GSK-3β, caspase-2, Bax, and cleaved caspase-7 and by activating anti-apoptotic proteins (Akt, β-catenin, Bcl-2, and cyclin D1). In contrast, at high concentrations (50 and 100 mM), it induces apoptosis by reversing these effects. Moreover, LiCl also alters the sodium and potassium levels thereby altering the membrane potential of MCF-7 cells. Thus it is inferred that LiCl exerts a dose-dependent biphasic effect on breast cancer cells (MCF-7) by altering the apoptotic/anti-apoptotic balance.

Lithium modulates cancer cell growth, apoptosis, gene expression and cytokine production in HL-60 promyelocytic leukaemia cells and their drug-resistant sub-clones

Lithium has been an FDA-approved and preferred drug for the treatment of mood disorders for many years, and cumulative evidence has pointed towards its potential use as an anti-cancer agent. Previous studies in our laboratory have demonstrated that lithium induces apoptotic cell death in HL-60 promyelocytes at concentrations of 10 mM and above. A lithium-tolerant HL-60 sub-clone, resistant to up to 15 mM lithium, was also generated and its growth profile reported. Treatment of cells with lithium resulted in a dose-dependent induction of p53, retinoblastoma (Rb) and bax expression which was accompanied by concomitant inhibition of bcl-2 expression as demonstrated using immunohistochemical microscopy. These results seem to suggest that lithium induced cell death in these cells by inhibiting expression of anti-apoptotic protein, bcl-2, while inducing higher expression of its pro-apoptotic counterparts which include bax. Expression of bax and bcl-2 is also linked to expression of inflammation-regulating cytokines. Using ELISA assays, lithium was demonstrated to induce production of pro-inflammatory cytokines, IL-6 and TNF-α, while inhibiting release of anti-inflammation-related IL-2 and IL-10 in a dose-dependent fashion. Our findings identify a critical function for lithium in modulating pro- versus anti-apoptotic gene expression and pro- versus anti-inflammatory cytokines in vitro and provide a rationale for suggesting a promising role of lithium in regulation of inflammation and cancer growth.

Effects of a glycogen synthase kinase-3β inhibitor (LiCl) on c-myc protein in intervertebral disc cells

Wnt/β-catenin (hereafter called Wnt) signaling is a key inducer and regulator of joint development, and is involved in the formation of bone and cartilage. We previously reported that Wnt signaling plays an essential role in the control of cell proliferation and cell senescence in intervertebral disc cells. In the present study, we provide evidence that the expression of c-myc, a key protein required for cell proliferation, is regulated by Wnt signaling. Our data also show that activation of Wnt signaling by LiCl, a Wnt signaling activator, leads to the suppression of c-myc promoter activity and expression. To ascertain whether Wnt signaling regulates the expression of c-myc, we measured both its transcript and protein expression. Following treatment with LiCl, c-myc expression was suppressed at both the mRNA and protein levels. In nucleus pulposus cells treated with c-myc, cell viability increased significantly, whereas treatment with a c-myc inhibitor decreased cell viability. Taken together, these results suggest that c-myc is an important factor that promotes the proliferation of nucleus pulposus cells. These findings provide new insight into the regulation and maintenance of cell proliferation in nucleus pulposus cells.

Proteomic analysis of lithium-induced gene expression in the rat hypothalamus

The hypothalamic proteomes were analyzed 1 and 6 hr after an intraperitoneal injection of lithium chloride or sodium chloride (0.15 M, 12 ml/kg). Results showed that expression of 14 and 32 proteomes was increased consistently by 1 hr and 6 hr of lithium treatment, respectively. Among them, tentative implications of glial fibrillary acidic protein, receptor-type protein tyrosine phosphatase, spectrin, and glutamate dehydrogenase in the lithium-induced activation of the hypothalamic-pituitary-adrenal axis, and conditioned taste aversion have been discussed. The proteomes listed in this study will provide, at least, a new insight to understand the molecular mechanism of lithium's action in the brain.

Porcine proximal tubular cells (LLC-PK1) are able to tolerate high levels of lithium chloride in vitro: assessment of the influence of 1-20 mM LiCl on cell death and alterations in cell biology and biochemistry

Lithium, a prophylactic drug for the treatment of bipolar disorder, is prescribed with caution due to its side effects, including renal damage. In this study porcine LLC-PK1 renal tubular cells were used to establish the direct toxicity of lithium on proximal cells and gain insights into the molecular mechanisms involved. In the presence of LiCl, cell proliferation exhibited insignificant decreases in a concentration-dependent manner, but once confluent, constant cell numbers were observed. Cell cycle studies indicated a small dose-dependent accumulation of cells in the G2/M stage after 24 h, as well as an increase in cells in the G0/G1 phase after treatment with 1-10 mM LiCl, but not at 20 mM LiCl. No evidence of apoptosis was observed based on cell morphology or DNA fragmentation studies, or evidence of protein expression changes for Bax, Bcl-2, and p53 proteins using immunocytochemistry. In addition caspases 3, 8 and 9 activity remained unaltered between control and lithium-treated cultures. To conclude, exposure to high concentrations of lithium did not result in overt toxic effects to LLC-PK1 renal cells, although LiCl did alter some aspects of cell behaviour, which could potentially influence function over time.

Lithium inhibits proliferation of human esophageal cancer cell line Eca-109 by inducing a G2/M cell cycle arrest

AIM: To investigate the effect of lithium on proliferation of esophageal cancer (EC) cells and its preliminary mechanisms.

METHODS: Eca-109 cells were treated with lithium chloride, a highly selective inhibitor of glycogen synthase kinase 3β (GSK-3β), at different concen-trations (2-30 mmol/L) and time points (0, 2, 4, 6 and 24 h). Cell proliferative ability was evaluated by 3-(4,5-dimethylthiazole-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay, and cell cycle distribution was examined by flow cytometry. Expressions of p-GSK-3β, β-catenin, cyclin B1, cdc2 and cyclin D1 protein were detected by Western blotting, and the subcellular localization of β-catenin was determined by immunofluorescence. The mRNA level of cyclin B1 was detected by reverse transcription polymerase chain reaction (RT-PCR).

RESULTS: Lithium could inhibit the proliferation of Eca-109 cells. Lithium at a concentration of 20 mmol/L lithium for 24 h produced obvious changes in the distribution of cell cycle, and increased the number of cells in G₂/M phase (P < 0.05 vs control group). Western blotting showed that lithium inhibited GSK-3β by Ser-9 phosphorylation and stabilized free β-catenin in the cytoplasm. Immunofluorescence further confirmed that free β-catenin actively translocated to the nucleus. Moreover, lithium slightly elevated cyclin D1 protein expression, whereas lowered the cyclin B1 expression after 24 h lithium exposure and no obvious change was observed for cdc2 protein.

CONCLUSION: Lithium can inhibit the proliferation of human esophageal cancer cell line Eca-109 by inducing a G₂/M cell cycle arrest, which is mainly mediated through the inhibition of lithium-sensitive molecule, GSK-3β, and reduction of cyclin B1 expression.

Lithium stabilizes the polarized lens epithelial phenotype and inhibits proliferation, migration, and epithelial mesenchymal transition

Posterior capsule opacification (PCO) is a common complication of cataract surgery caused by epithelial mesenchymal transition (EMT) and aberrant lens cell growth. One path to prevention depends on maintaining the quiescent lens epithelial phenotype. Here we report that lithium chloride (LiCl) is a potent stabilizer of the lens epithelial phenotype. In lens epithelial explants (controls), at low cell density, cells readily depolarized, spread out, and proliferated. By contrast, in the presence of LiCl, cells did not spread out or exhibit migratory behaviour. Using concentrations of 1-30 mM LiCl we also showed that cell proliferation is inhibited in a dose-dependent manner. Confocal microscopy and immunohistochemistry for ZO-1 and E-cadherin showed that LiCl treatment maintained tight junctions at the apical margins of cells. Taken together with measurements of cell heights, this showed that the cells in LiCl-treated explants maintained the apical baso-lateral polarity and cobblestone-like packing that is characteristic of lens epithelial cells in vivo. Significantly, the effects of LiCl also extended to blocking the potent EMT/cataract-promoting effects of transforming growth factor beta (TGFbeta) on lens epithelial cells. In TGFbeta-treated explants, cells progressively dissociated from one another, taking on various elongated spindle shapes and strongly expressing alpha-smooth muscle actin (alpha-SMA). These features are characteristic of PCO. In both rat and human capsulorhexis explants, LiCl treatment effectively blocked the accumulation of alpha-SMA and maintained the cells in a polarized, adherent, cobblestone-packed monolayer. These findings highlight the feasibility of applying molecular strategies to stabilize lens epithelial cells and prevent aberrant differentiation and growth that leads to cataract.

MG132 induced apoptosis is associated with p53-independent induction of pro-apoptotic Noxa and transcriptional activity of beta-catenin

Noxa is a pro-apoptotic BH3-only member of the Bcl-2 family of proteins that is up-regulated at a transcriptional level by the nuclear protein p53 in response to cellular stresses such as DNA damage or growth factor deprivation. Noxa is able to interact with anti-apoptotic members of the Bcl-2 family and causes release of cytochrome c into the cytosol, leading to the activation of caspases and induction of apoptosis. Here we demonstrate that MG132, a proteasomal inhibitor, rapidly induces Noxa mRNA and protein in two human cell lines, T/C28a and Saos2. The induction of Noxa is associated with a significant reduction in the number of metabolically active cells over the first 24 h of exposure to MG132 and progressive activation of caspase-3, a hallmark of caspase-dependent apoptosis. Partial rescue of the phenotype is observed when cells are transfected with Noxa siRNA prior to treatment with MG132, indicating functional significance of the induction of Noxa. p53 has previously been shown to be non-functional in the T/C28a cell line and is absent by Western blotting in Saos2 cells, suggesting that the induction of Noxa is through a p53 independent mechanism. Western blotting and confocal microscopy showed that total beta-catenin protein is increased in both cell lines at the time of Noxa induction, with the bulk of the beta-catenin present in the nucleus. Transfection with the Tcf reporter vector pTOPFLASH confirms that treatment with MG132 leads to early increased transcriptional activity of beta-catenin in both T/C28a and Saos2 cells. However, although over-expression of transcriptionally active beta-catenin in T/C28a cells also induced apoptosis through a p53-independent mechanism, the levels of Noxa protein were unchanged, suggesting that beta-catenin mediated signaling and Noxa may play independent roles in MG132 induced apoptosis. In summary, our results demonstrate that MG132 induces the pro-apoptotic protein Noxa via a p53-independent mechanism that leads to caspase-dependent apoptosis. This is the first report showing that treatment with MG132 induces Noxa. This study also provides further evidence for a link between beta-catenin mediated signaling and the induction of apoptosis.

Early gene response in lithium chloride induced apoptosis

Depending on the cellular context, lithium chloride can lead to enhanced proliferation, cell cycle arrest or apoptosis in mammalian cells. Although substantial work has been made to elucidate the downstream events in the case of lithium chloride-induced cellular proliferation, the molecular response to lithium chloride treatment in the apoptotic scenario is largely undefined. We have used quadruplicate human cDNA arrays with 8000 targets to analyze the early gene response in cultures of human T/C28a cells that undergo apoptosis in response to 20 mM lithium chloride treatment. Incubation of cell cultures with 20 mM lithium chloride for five hours caused alterations in the steady-state mRNA levels of a large number of genes. RT-PCR and real-time RT-PCR confirmed the array results for ten of eleven selected targets. In addition to one protein primarily associated with apoptosis, genes identified as differentially expressed based on microarray data mainly encode proteins involved in basic cellular functions such as signaling, cell cycle control and growth, cell-cell interaction, solute transport and transcription control. We present a list of 50 genes that were differentially expressed in response to lithium chloride treatment and which may represent a reference for further studies to define the pathways governing the apoptotic response to lithium chloride.

Changes in cellular composition of kidney collecting duct cells in rats with lithium-induced NDI

Lithium treatment for 4 wk caused severe polyuria, dramatic downregulation in aquaporin-2 (AQP-2) expression, and marked decrease in AQP-2 immunoreactivity with the appearance of a large number of cells without AQP-2 labeling in the collecting ducts after lithium treatment. Surprisingly, this was not all due to an increase in AQP-2-negative principal cells, because double immunolabeling revealed that the majority of the AQP-2-negative cells displayed [H(+)]ATPase labeling, which identified them as intercalated cells. Moreover, multiple [H(+)]ATPase-labeled cells were adjacent, which was never seen in control rats. Quantitation confirmed a significant decrease in the fraction of collecting duct cells that exhibited detectable AQP-2 labeling compared with control rats: in cortical collecting ducts, 40 +/- 3.4 vs. 62 +/- 1.8% of controls (P < 0.05; n = 4) and in inner medullary collecting ducts, 58 +/- 1.6 vs. 81 +/- 1.3% of controls (P < 0.05; n = 4). In parallel, a significant increase in the fraction of intercalated ([H(+)]ATPase-positive) cells was shown. Urine output, whole kidney AQP-2 expression, cellular organization, and the fractions of principal and intercalated cells in cortex and inner medulla returned to control levels after 4 wk on a lithium-free diet following 4 wk on a lithium-containing diet. In conclusion, lithium treatment not only decreased AQP-2 expression, but dramatically and reversibly reduced the fraction of principal cells and altered the cellular organization in collecting ducts. These effects are likely to be important in lithium-induced nephrogenic diabetes insipidus.

Glucocorticoids inhibit cell cycle progression in differentiating osteoblasts via glycogen synthase kinase-3beta

Differentiating osteoblasts in culture undergo a commitment stage, during which cobblestone-like cells grow to high density past confluency. In contrast to earlier proliferative stages, the cell cycle during this commitment stage is inhibited by glucocorticoids (GC). Chronic GC treatment also impedes mineral deposition if steroid administration commences early enough during commitment. This study defines a role for glycogen synthase kinase-3beta (GSK3beta) and its target, c-Myc, in the GC-sensitive osteoblast persistent cell cycle. c-Myc levels decreased as cells reached confluence, but then increased during growth to high density. GC administration at this stage resulted in down-regulation of c-Myc. This was accompanied by GC-mediated attenuation of GSK3beta Ser(9) inhibitory phosphorylation and increased GSK3beta kinase activity. Down-regulation of c-Myc was attributable to enhanced Thr(58) phosphorylation, leading to accelerated degradation. In contrast, GC did not inhibit the c-Myc synthesis rate or the level of beta-catenin, a transcriptional coactivator of c-myc. The attenuated cell cycle and the reduced c-Myc level were returned to control levels by specific inhibition of GSK3beta using lithium chloride. These results suggest that tonal GSK3beta repression at the cobblestone stage of osteoblast differentiation permits osteoblast growth to high density. GC interfere with this growth-permissive axis by GSK3beta activation, resulting in c-Myc down-regulation and impediment of the G(1)/S cell cycle transition.

Overexpression of components of the Frizzled-Dishevelled cascade results in apoptotic cell death, mediated by beta-catenin

Frizzled (fz) functions as a 7-transmembrane receptor in the Frizzled-Dishevelled signal transduction cascade. It is involved in architectural control of development in species as divergent as Drosophila and vertebrates. Regulation of multicellular architecture requires control of cell alignment, but also involves an equilibrium among cell proliferation, differentiation, and apoptosis. Recently, modulation of the Frizzled-Dishevelled (Dvl) cascade has been related to apoptosis. However, the role of beta-catenin, a second messenger in the Frizzled-Dishevelled cascade, in programmed cell death is a matter of debate. To elucidate the role of this cascade in apoptosis, we studied the effect of overexpression of fz1, fz2, dvl1, and beta-catenin. The signal transduction pathway and the involvement of beta-catenin were further investigated by using different inhibitors. These experiments were performed in different cell types: COS7, 293, and PC12. Overexpression of fz1, fz2, and dvl1 induced apoptosis in COS7 and 293 cells. beta-Catenin appears to be the mediator for this process since beta-catenin overexpression as well as lithium and valproate induced apoptosis. In contrast, lithium treatment did not result in apoptosis in PC12 cells. We conclude that different components of the Frizzled-Dishevelled cascade can induce apoptosis, but that this effect is dependent on the cell type.

Lithium at 50: have the neuroprotective effects of this unique cation been overlooked?

Recent advances in cellular and molecular biology have resulted in the identification of two novel, hitherto completely unexpected targets of lithium's actions, discoveries that may have a major impact on the future use of this unique cation in biology and medicine. Chronic lithium treatment has been demonstrated to markedly increase the levels of the major neuroprotective protein, bcl-2 in rat frontal cortex, hippocampus, and striatum. Similar lithium-induced increases in bcl-2 are also observed in cells of human neuronal origin, and are observed in rat frontal cortex at lithium levels as low as approximately 0.3 mmol/L. Bcl-2 is widely regarded as a major neuroprotective protein, and genetic strategies that increase bcl-2 levels have demonstrated not only robust protection of neurons against diverse insults, but have also demonstrated an increase the regeneration of mammalian CNS axons. Lithium has also been demonstrated to inhibit glycogen synthase kinase 3 beta (GSK-3 beta), an enzyme known to regulate the levels of phosphorylated tau and beta-catenin (both of which may play a role in the neurodegeneration observed in Alzheimer's disease). Consistent with the increases in bcl-2 levels and inhibition of GSK-3 beta, lithium has been demonstrated to exert robust protective effects against diverse insults both in vitro and in vivo. These findings suggest that lithium may exert some of its long term beneficial effects in the treatment of mood disorders via underappreciated neuroprotective effects. To date, lithium remains the only medication demonstrated to markedly increase bcl-2 levels in several brain areas; in the absence of other adequate treatments, the potential efficacy of lithium in the long term treatment of certain neurodegenerative disorders may be warranted.

Apoptosis: clinical relevance and pharmacological manipulation

Apoptosis, often synonymously used with the term 'programmed cell death', is an active, genetically controlled process that removes unwanted or damaged cells. Suppression, overexpression or mutation of a number of genes which orchestrate the apoptotic process are associated with disease. The diseases in which apoptosis has been implicated can be grouped into 2 broad groups: those in which there is increased cell survival (i.e. associated with inhibition of apoptosis) and those in which there is excess cell death (where apoptosis is overactive). Diseases in which there is an excessive accumulation of cells include cancer, autoimmune disorders and viral infections. Deprivation of trophic factors is known to induce apoptosis in cells dependent on them for survival. This fact has been exploited in the use of antiandrogens or antiestrogens in the management of prostate or breast cancer. Haemopoietic growth factors like granulocyte-macrophage colony stimulating factor (GM-CSF) or interleukin-3 prevent apoptosis in target cells and modulation of levels of these factors has been tried in the prevention of chemotherapy-induced myelosuppression. Until recently, it was thought that cytotoxic drugs killed target cells directly by interfering with some life-maintaining function. However, of late, it has been shown that exposure to several cytotoxic drugs with disparate mechanisms of action induces apoptosis in both malignant and normal cells. Physiological regulation of cell death is essential for the removal of potentially autoreactive lymphocytes during development and the removal of excess cells after the completion of an immune response. Recent work has clearly demonstrated that dysregulation of apoptosis may underlie the pathogenesis of autoimmune diseases by allowing abnormal autoreactive lymphocytes to survive. AIDS and neurodegenerative disorders like Alzheimer's or Parkinson's disease represent the most widely studied group of disorders where an excess of apoptosis has been implicated. Amyotrophic lateral sclerosis, retinitis pigmentosa, epilepsy and alcoholic brain damage are other neurological disorders in which apoptosis has been implicated. Apoptosis has been reported to occur in conditions characterised by ischaemia, e.g. myocardial infarction and stroke. The liver is a site where apoptosis occurs normally. This process has also been implicated in a number of liver disorders including obstructive jaundice. Hepatic damage due to toxins and drugs is also associated with apoptosis in hepatocytes. Apoptosis has also been identified as a key phenomenon in some diseases of the kidney, i.e. polycystic kidney, as well as in disorders of the pancreas like alcohol-induced pancreatitis and diabetes.