Study on the novel factors regulating mitochondrial dynamics

Mitochondria are highly dynamic organelles and undergo continuous fission and fusion events in physiological situations. It was observed that mitochondrial morphology and number are changed in living cells during cellular differentiation, development, and under pathological conditions including muscle dystrophy, cardiomyopathy, and cancer. Defined sets of proteins are known to mediate mitochondrial fission and fusion and to constitute regulatory components controlling mitochondrial dynamics. In the present study, we first investigated mitochondrial dynamics during the cell cycle progression, and found that mitochondria exist as filamentous network structures throughout the cell cycle progression, changing their morphology, distribution, and abundance. In addition, we found that a mouse homolog of human DNA polymerase delta interacting protein 38, referred to as Mitogenin I, and mitochondrial single-stranded DNA-binding protein (mtSSB), identified as upregulated genes in the heart of mice with juvenile visceral steatosis, play a role in the regulation of mitochondrial morphology.     

Mitochondria-targeted peptide antioxidants: Novel neuroprotective agents

Increasing evidence suggests that mitochondrial dysfunction and oxidative stress play a crucial role in the majority of neurodegenerative diseases. Mitochondria are a major source of intracellular reactive oxygen species (ROS) and are particularly vulnerable to oxidative stress. Oxidative damage to mitochondria has been shown to impair mitochondrial function and lead to cell death via apoptosis and necrosis. Because dysfunctional mitochondria will produce more ROS, a feed-forward loop is set up whereby ROS-mediated oxidative damage to mitochondria favors more ROS generation, resulting in a vicious cycle. It is now appreciated that reduction of mitochondrial oxidative stress may prevent or slow down the progression of these neurodegenerative disorders. However, if mitochondria are the major source of intracellular ROS and mitochondria are most vulnerable to oxidative damage, then it would be ideal to deliver the antioxidant therapy to mitochondria. This review will summarize the development of a novel class of mitochondria-targeted antioxidants that can protect mitochondria against oxidative stress and prevent neuronal cell death in animal models of stroke, Parkinson's disease, and amyotrophic lateral sclerosis.     

Autofluorescence microscopy: a non-destructive tool to monitor mitochondrial toxicity

Visualization of NADH by fluorescence microscopy makes it possible to distinguish mitochondria inside living cells, allowing structure analysis of these organelles in a non-invasive way. Mitochondrial morphology is determined by the occurrence of mitochondrial fission and fusion. During normal cell function mitochondria appear as elongated tubular structures. However, cellular malfunction induces mitochondria to fragment into punctiform, vesicular structures. This change in morphology is associated with the generation of reactive oxygen species (ROS) and early apoptosis. The aim of this study is to demonstrate that autofluorescence imaging of mitochondria in living eukaryotic cells provides structural and morphological information that can be used to assess mitochondrial health. We firstly established the illumination conditions that do not affect mitochondrial structure and calculated the maximum safe light dose to which the cells can be exposed. Subsequently, sequential recording of mitochondrial fluorescence was performed and changes in mitochondrial morphology were monitored in a continuous non-destructive way. This approach was then used to assess mitochondrial toxicity induced by potential toxicants exposed to mammalian cells. Both mouse and human cells were used to evaluate mitochondrial toxicity of different compounds with different toxicities. This technique constitutes a novel and promising approach to explore chemical induced toxicity because of its reliability to monitor mitochondrial morphology changes and corresponding toxicity in a non-invasive way.     

Differential responses to docosahexaenoic acid in primary and immortalized cardiac cells

The importance of dietary polyunsaturated fatty acids (PUFAs) in the reduction of cardiovascular disease has been recognized for many years. Docosahexaenoic acid (22:6n3, DHA) is an n-3 PUFA known to affect numerous biological functions and provide cardioprotection; however, the exact molecular and cellular protective mechanism(s) remain unknown. In contrast, DHA also possesses many anti-tumorgenic properties including suppressing cell growth and inducing apoptosis. In the present study, we investigated the effect of DHA toward H9c2 cells (an immortalized cardiac cell line) and neonatal primary cardiomyocytes (NCM). Cells were treated with 0 μM, 10 μM or 100 μM DHA for upto 48 h. Cell viability and mitochondrial activity were assayed at different time points. DHA caused a significant time- and dose-dependent decrease in cell viability and mitochondrial activity in H9c2 cells but not NCM. In addition, DHA decreased levels of TGF-β1 but increased IL-6 release in H9c2 cells. Significant induction of apoptosis was observed only in H9c2 cells, which involved activation of caspase-8 and -3 activities with a marked release of cytochrome c from mitochondria. DHA-induced severe mitochondrial damage resulting in a fragmented and punctated morphology with corresponding loss of mitochondrial membrane potential within 3 h, prior to activation of caspases and cytochrome c release at 6 h in H9c2 cells. Our data indicate that DHA treatment targets mitochondria, triggering collapse of mitochondrial membrane potential, increasing cellular stress and mitochondrial fragmentation resulting in apoptosis in immortalized cardiac cells, H9c2, but not neonatal primary cardiomyocyte.     

Hesperetin induces an apoptosis-triggered extrinsic pathway and a p53- independent pathway in human lung cancer H522 cells

We studied the chemoprevention property of hesperetin on H522 cells using MTT, an apoptosis assay, an analysis of cell cycle progression, and the mitochondrial membrane potential, and apoptotic marker gene expression was determined using quantitative PCR. Hesperetin enhanced apoptotic cell death and mitochondrial membrane potential loss in H522 cells. Hesperetin up-regulated the levels of Fas, FADD, and caspase-8 expression and downregulted the levels of caspase-3 and caspase-9, p53, and Bax expression in H522 cells. This study shows that hesperetin induces apoptosis in H522 cells via a pathway independentof p53 and Bax but triggers the death-receptor Fas-initiated FADD/ caspase-8-dependent apoptotic pathway.     

A multi-functional organelle mitochondrion is involved in cell death, proliferation and disease

The mitochondrion, long considered an organelle specific to energy metabolism, is in fact multi-functional and involved in many diseases. Mitochondrial DNA accumulates somatic mutations during aging, the progression of cancer and diabetes. Most cancer cells contain homoplasmic mutations in the mitochondrial genome. Although little is known about the contributions of mutations to carcinogenesis, some mutations in the nuclear genes encoding mitochondrial proteins have been identified as responsible for certain familial cancers. Mitochondria play an essential role in generating the germ line by releasing mitochondrial ribosomal RNAs, by which the germ line transfers the genetic information necessary for life to the next generation. Collaboration between mitochondria and the cytosol occurs in several metabolic pathways. Many enzymes involved in synthesizing uridine, heme and steroids and in the urea cycle are located inside mitochondria. Notably, a reaction involved in the synthesis of UMP is coupled with the energized state of mitochondria. Thus, the synthesis of DNA and RNA should be indirectly coupled with the energized state of mitochondria. Additionally, storing calcium is an important role of mitochondria. Calcium functions as a second messenger in signal transduction, however, it also activates several proteinases or lipases to induce damage. The mitochondrion plays a significant role in necrosis and is a center for apoptosis, determining its initiation, regulation and execution. Thus, the mitochondrion is widely involved in cell proliferation, cell death and disease.     

Cell cycle arrest induced in human breast cancer cells by cyclin-dependent kinase inhibitors: a comparison of the effects exerted by roscovitine and olomoucine

Cyclin-dependent kinases (CDKs) are serine/threonine kinases that play a key role in the regulation of the cell cycle progression. In proliferating cells, distinct CDKs activated upon complexing with specific cyclins and upon site-specific phosphorylation coordinate in an orchestrated way the appropriate transition between consecutive phases of the cell cycle. Aberrant expression or altered activity of distinct CDK complexes results in escape of cells from the cell cycle control and leads to malignant transformation. Therefore, the inhibition of CDKs in malignant cells provides a new strategy in the fight against cancer. Recently, selective CDK inhibitors targeting distinct CDKs were developed. They represent promising anti-cancer drugs due to their strong anti-proliferative efficacy combined with a relative low direct cytotoxicity. The aim of this study was to compare the effect of two related CDK inhibitors: roscovitine (ROSC) and olomoucine (OLO) on the cell cycle progression in human breast cancer MCF-7 cells. Both examined CDK inhibitors differentially affected the cell cycle progression in MCF-7 cels. Whereas ROSC arrested cells in G(2)/M, OLO inhibited cells at S to G(2) transition and increased the number of cells residing in the S-phase. Moreover, both CDK inhibitors modulated the cell cycle progression with distinct kinetics. Accumulation of G(2)/M-arrested cells beginning 6 h after exposure of cells to ROSC coincided with a strong up-regulation of the p53. Interestingly, ROSC triggered apoptosis in MCF-7 cells by activation of mitochondrial pathway. Loss of the integrity of mitochondrial membrane observed after exposure of cells to ROSC for 6 h led to release of distinct mitochondrial proteins, e.g. apoptosis inducing factor (AIF). In contrast to ROSC, OLO-induced cell cycle changes could be detected after 12 h of the treatment. OLO did not up-regulate p53 protein. It indicates that both examined CDK inhibitors are selective and block the cell cycle progression of human breast carcinoma cells at different phases.     

Involvement of enniatins-induced cytotoxicity in human HepG2 cells

Enniatins (ENNs) are mycotoxins found in Fusarium fungi and they appear in nature as mixtures of cyclic depsipeptides. The ability to form ionophores in the cell membrane is related to their cytotoxicity. Changes in ion distribution between inner and outer phases of the mitochondria affect to their metabolism, proton gradient, and chemiosmotic coupling, so a mitochondrial toxicity analysis of enniatins is highly recommended because they host the homeostasis required for cellular survival. Two ENNs, ENN A and ENN B on hepatocarcinoma cells (HepG2) at 1.5 and 3 μM and three exposure times (24, 48 and 72 h) were studied. Flow cytometry was used to examine their effects on cell proliferation, to characterize at which phase of the cell cycle progression the cells were blocked and to study the role of the mitochondrial in ENNs-induced apoptosis. In conclusion, apoptosis induction on HepG2 cells allowed to compare cytotoxic effects caused by both ENNs, A and B. It is reported the possible mechanism observed in MMP changes, cell cycle analysis and apoptosis/necrosis, identifying ENN B more toxic than ENN A.     

Defective mitochondrial function and motility due to mitofusin 1 overexpression in insulin secreting cells

Mitochondrial dynamics and distribution is critical for their role in bioenergetics and cell survival. We investigated the consequence of altered fission/fusion on mitochondrial function and motility in INS-1E rat clonal β-cells. Adenoviruses were used to induce doxycycline-dependent expression of wild type (WT-Mfn1) or a dominant negative mitofusin 1 mutant (DN-Mfn1). Mitochondrial morphology and motility were analyzed by monitoring mitochondrially-targeted red fluorescent protein. Adenovirus-driven overexpression of WT-Mfn1 elicited severe aggregation of mitochondria, preventing them from reaching peripheral near plasma membrane areas of the cell. Overexpression of DN-Mfn1 resulted in fragmented mitochondria with widespread cytosolic distribution. WT-Mfn1 overexpression impaired mitochondrial function as glucose- and oligomycin-induced mitochondrial hyperpolarization were markedly reduced. Viability of the INS-1E cells, however, was not affected. Mitochondrial motility was significantly reduced in WT-Mfn1 overexpressing cells. Conversely, fragmented mitochondria in DN-Mfn1 overexpressing cells showed more vigorous movement than mitochondria in control cells. Movement of these mitochondria was also less microtubule-dependent. These results suggest that Mfn1-induced hyperfusion leads to mitochondrial dysfunction and hypomotility, which may explain impaired metabolism-secretion coupling in insulin-releasing cells overexpressing Mfn1.     

Induction of apoptosis by YTX in myoblast cell lines via mitochondrial signalling transduction pathway

Yessotoxin (YTX) can induce apoptotic events in myoblast L6 and BC3H1 cell lines from rat and mouse, respectively. The present study indicates that apoptosis induced by YTX in these cell lines can occur through activation of the mitochondrial pathway indicating an intracellular response. Terminal events during mitochondrial-mediated apoptosis involve perturbations to mitochondria resulting in loss of mitochondrial membrane potential (ΔΨ_m), permeability transition pore (PTP) opening and the release of proapoptotic factors cytochrome c, smac/DIABLO into the cytosol. Results from western blotting, electron and fluorescent microscopy of YTX-treated myoblast cells provided experimental data for evaluation of cytochrome c, smac/DIABLO release and caspase-9 activation. Loss of mitochondrial membrane potential and swelling of mitochondria indicated an active role of mitochondria during the early phase of apoptosis in L6 and BC3H1 cells after YTX exposure. These observations show that YTX targets mitochondria and involve activation of a cascade of events through mitochondrial regulation.     

Morphological and functional alterations in human proximal tubular cell line induced by low level inorganic arsenic: evidence for targeting of mitochondria and initiated apoptosis

The kidney is a known target organ for arsenic and is critical for both arsenic biotransformation and elimination. Previous studies have demonstrated that at high doses (ppm) inorganic arsenic is toxic to mitochondria primarily by affecting cellular respiration. However, the effect of inorganic arsenic on mitochondria after low level exposures is not known, particularly in the kidney. Thus the functional and morphological effects of low level inorganic arsenic were investigated in a human proximal tubular cell line, HK-2. Mitochondrial function was assessed at subcytotoxic concentrations of arsenite (< or = 10 microm) by examining the alteration of the mitochondrial membrane potential using MitoTracker Red, a mitochondrion selective dye. In a subset of cells, subcytotoxic arsenite led to mitochondrial membrane depolarization, which could subsequently lead to permeability transition and apoptosis. Subcytotoxic arsenite also induced translocation of phosphatidylserine, indicative of early-stage apoptosis. To confirm whether subcytotoxic arsenite induces cellular and/or mitochondrial morphological alterations consistent with initiated apoptosis, HK-2 cells were evaluated with transmission electron microscopy. Classic morphology of apoptosis was not observed with subcytotoxic arsenite exposures; however, evidence of necrotic changes in the cytoplasmic structure and mitochondrial morphology were apparent. Therefore, based on depolarization of mitochondria and the externalization of phosphatidylserine, HK-2 cells appear to initiate apoptosis following subcytotoxic arsenite insult, but morphological changes indicate that HK-2 cells fail to complete apoptosis and ultimately undergo necrosis. Therefore, subcytotoxic arsenite can be sufficiently toxic to mitochondria that they lose their ability to keep the cell on course for apoptotic cell death.     

Lipophilic caffeic and ferulic acid derivatives presenting cytotoxicity against human breast cancer cells

In the present work, lipophilic caffeic and ferulic acid derivatives were synthesized, and their cytotoxicity on cultured breast cancer cells was compared. A total of six compounds were initially evaluated: caffeic acid (CA), hexyl caffeate (HC), caffeoylhexylamide (HCA), ferulic acid (FA), hexyl ferulate (HF), and feruloylhexylamide (HFA). Cell proliferation, cell cycle progression, and apoptotic signaling were investigated in three human breast cancer cell lines, including estrogen-sensitive (MCF-7) and insensitive (MDA-MB-231 and HS578T). Furthermore, direct mitochondrial effects of parent and modified compounds were investigated by using isolated liver mitochondria. The results indicated that although the parent compounds presented no cytotoxicity, the new compounds inhibited cell proliferation and induced cell cycle alterations and cell death, with a predominant effect on MCF-7 cells. Interestingly, cell cycle data indicates that effects on nontumor BJ fibroblasts were predominantly cytostatic and not cytotoxic. The parent compounds and derivatives also promoted direct alterations on hepatic mitochondrial bioenergetics, although the most unexpected and never before reported one was that FA induces the mitochondrial permeability transition. The results show that the new caffeic and ferulic acid lipophilic derivatives show increased cytotoxicity toward human breast cancer cell lines, although the magnitude and type of effects appear to be dependent on the cell type. Mitochondrial data had no direct correspondence with effects on intact cells suggesting that this organelle may not be a critical component of the cellular effects observed. The data provide a rational approach to the design of effective cytotoxic lipophilic hydroxycinnamic derivatives that in the future could be profitably applied for chemopreventive and/or chemotherapeutic purposes.     

2,4-dinitrophenol induces G1 phase arrest and apoptosis in human pulmonary adenocarcinoma Calu-6 cells.

2,4-dinitrophenol (DNP) is an uncoupler of oxidative phosphorylation in the mitochondria. Here, we investigated the effect of DNP on the growth of Calu-6 lung cancer cells in view of cell cycle, apoptosis, ROS production and GSH content. DNP dose-dependently decreased cell viability at 72 h (EC50 of about 200 microM) as measured by a MTT assay. The lower doses of DNP induced a G1 arrest of the cell cycle in Calu-6 cells. Analysis of the cell cycle regulatory proteins demonstrated that DNP decreased the steady-state levels of cyclin proteins and cyclin dependent kinase (CDK), but increased the protein levels of cyclin dependent kinase inhibitor (CDKI) p27. DNP also caused a marked increase in apoptosis, as evidenced by DNA fragmentation (sub-G1 DNA content), DAPI staining, the loss of mitochondrial membrane potential (DeltaPsim), externalization of phosphatidylserine (PS). In addition, DNP-treated cells significantly increased the intracellular H2O2 and O2.- levels. All of caspase inhibitors could markedly rescue Calu-6 cells from DNP-induced cell death and only pan-caspase inhibitor, Z-VAD-FMK, could slightly prevent the loss of mitochondrial membrane potential (DeltaPsim). However, none of the caspase inhibitors reduced the increased H2O2 levels, but the increased O2.- levels was slightly attenuated by pan-caspase inhibitor. In addition, the depletion of GSH content in DNP-treated cells was prevented by all of caspase inhibitors. In conclusion, DNP, which induced ROS and reduced GSH content, inhibited the growth of Calu-6 cells via cell cycle arrest at G1 phase and apoptosis.     

Ciclopirox protects mitochondria from hydrogen peroxide toxicity

1 The mitochondrial respiratory chain produces reactive oxygen species (ROS) during normal electron transport. Despite producing ROS, mitochondria are vulnerable to oxidative stress. Mitochondrial dysfunction has been associated with many degenerative diseases, making it important to identify compounds that protect mitochondria from ROS-mediated toxicity. Here we report that ciclopirox (CPX) blocks H2O2-induced mitochondrial injury by maintaining mitochondrial transmembrane potential (Deltapsim). 2 CPX completely blocked H2O2-stimulated release of lactate dehydrogenase (a marker of cell death) and decrease in MTT reduction (a marker of mitochondrial function) in adenocarcinoma SK-HEP-1 cells. 3 H2O2 rapidly depolarized the Deltapsim, and CPX blocked this H2O2-stimulated Deltapsim decrease. Similar data were obtained in experiments using mitochondria isolated from rat liver. 4 Furthermore, CPX effectively inhibited H2O2-induced mitochondrial permeability transition pore (MPTP) opening. In de-energized mitochondria, however, CPX did not inhibit Ca2+-evoked MPTP opening, indicating that CPX is not a direct inhibitor of the MPTP. 5 Oxygen consumption studies showed that in the presence of pyruvate and malate CPX restored the rate of state 3 to state 4 respiration decreased by H2O2. Consistent with this, CPX replenished ATP levels lowered by H2O2. 6 The present results indicate that CPX protects SK-HEP-1 cells from H2O2 cytotoxicity by inhibiting Deltapsim decrease and indirectly preventing MPTP opening.     

As2O3-induced oxidative stress and cycle progression in a human intestinal epithelial cell line (Caco-2).

Foods and drinking water are the main routes for human exposure to inorganic arsenic, the intestinal epithelium being the first barrier against such exogenous toxicants. The present study evaluates the effect of As(III) (0.5-25 microM) upon Caco-2 cells as an intestinal epithelia model. Cell viability, intracellular formation of reactive oxygen species (ROS), mitochondrial membrane potential (Deltapsim) changes, and cell cycle distribution in exposed cultures were evaluated. The intracellular production of ROS was seen to increase in a non-dose dependent manner at all concentrations tested, with impairment of cell mitochondrial enzyme function secondary to a loss of Deltapsim. Concentrations between 0.5 and 5 microM induce cell cycle transition from phase G1 to phase S, with no significant alteration in the proportion of cells in phase G2. These data suggest that As(III) could induce intestinal oxidative stress-cytotoxicity at mitochondrial functional level, and affect cell cycle progression. The data presented in this work may also suggest the impairment of essential survival processes in Caco-2 cells, induced after exposure to As(III) (1-25 microM). Oxidative stress and alteration of mitochondrial functionality could be early indicators of arsenic-induced cytotoxicity, with the resulting abnormal progression of the cell cycle.     

抑制二氢乳清酸脱氢酶的表达对线粒体功能的影响

目的 探讨通过抑制二氢乳清酸脱氢酶(DHODH)的表达对线粒体功能状态的影响.方法 采用siRNA沉默技术抑制宫颈癌HeLa细胞中DHODH的表达,检测细胞增殖、细胞周期状况和线粒体相应功能指标(线粒体膜电位和活性氧自由基).结果 DHODH表达下调后细胞增殖减缓(停滞于G2/M期),加入外源性尿苷虽可激活DHODH嘧啶合成反应旁路,却并不能缓解增殖减缓.DHODH缺失降低了线粒体膜电位(MMP)并使活性氧自由基(ROS)的产量增加,线粒体DNA数量减少.结论 DHODH在形成线粒体氧化呼吸复合物中发挥了相应的重要作用,对米勒综合征形成及线粒体调节细胞活力产生了重要影响.     

Induction of caspase-3-dependent apoptosis in human leukemia HL-60 cells by δ-elemene

δ-Elemene, an antitumor component, is a chemical compound isolated from Curcuma wenyujin, a Chinese traditional herb. We examined whether δ-elemene could inhibit cell growth and cell cycle progression and induce apoptosis in human leukemia HL-60 cells. The results demonstrated that δ-elemene induces significant apoptosis of HL-60 cells, as shown by MTT assay, annexin V (AnV) binding of externalized phosphatidylserine (PS), and the mitochondrial probe JC-1 using flow cytometry. HL-60 cells treated with δ-elemene showed high percentages in the early apoptotic and late apoptoctic/necrotic stages, as well as caspase-3 activation of HL-60 cells. By monitoring the changes in cell cycle profiles, we confirmed that δ-elemene could interfere with the cell cycle in the G2/M phase and induce apoptosis in HL-60 cells in a time-dependent manner. Caspase-3 plays a direct role in proteolytic cleavage of the cellular proteins responsible for progression to apoptosis. Therefore we examined apoptosis in HL-60 cells after exposure to δ-elemene and measured caspase-3 activities with or without Z-Val-Ala-Asp-fluoromethylketone (z-VAD-fmk, a broad-spectrum caspase inhibitor) pretreatment using flow cytometric analysis. The results showed that δ-elemene could induce caspase-3 activation as detected by the decrease in δ-elemene-induced caspase-3 activities after treatment with z-VAD-fmk. In the present study, δ-elemene activated typical caspase-dependent apoptosis in HL-60 cells, as demonstrated by an inhibitory effect of z-VAD-fmk on this cell death. During δ-elemene-induced apoptosis, cytochrome c and apoptosis-inducing factor were released into the cytosol and BAX was translocated from the cytosol to mitochondria. However, these were not prevented by z-VAD-fmk. In conclusion, our study demonstrated that δ-elemene could induce G2/M cell cycle transition and trigger apoptosis through a caspase-3-dependent pathway.     

Protective effect of curcumin, silymarin and N-acetylcysteine on antitubercular drug-induced hepatotoxicity assessed in an in vitro model

Tuberculosis (TB) is highly endemic in India. The first-line anti-TB therapy (ATT) involving isoniazid (INH), rifampicin and pyrazinamide causes hepatotoxicity in approximately 11.5% of Indian patients. Studies have shown that ATT-induced hepatotoxicity is primarily due to oxidative stress caused by the drugs and metabolites. Herbal drugs with antioxidative properties have been tested in animal studies and clinical trials for the management of hepatotoxicity. The objective of this study was to investigate the role of curcumin (CUR), silymarin (SILY) and N-acetylcysteine (N-ACET) on hepatotoxicity by ATT drugs using an in vitro model of human hepatocellular carcinoma cell line (HepG2). HepG2 cells were treated with ATT drugs alone or along with CUR, SILY or N-ACET for a 48-h duration. The cells were monitored for viability, morphology, respiring mitochondria and cell cycle. Our results suggest that the presence of hepatoprotective drugs during treatment of HepG2 cells with ATT drugs lowers the hepatotoxic effect of the latter. This is observed in terms of (a) increased cell viability, (b) healthy-looking cell morphology as revealed by phase contrast microscopy, (c) active respiring cells as observed with confocal microscopy upon staining with a mitochondrial membrane-specific dye, MitoTracker(?) Red, and reduction in the sub-G(1) peak in cell cycle analysis by flow cytometry. Our results suggest that these hepatoprotective drugs need to be further explored as potential adjuvant therapy along with ATT drugs.