Drug delivery to mitochondria: the key to mitochondrial medicine

doi:10.1016/S0169-409X(99)00069-1

Advanced Drug Delivery Reviews

Volume 41, Issue 2, 30 March 2000, Pages 235-250

https://doi.org/10.1016/S0169-409X(99)00069-1 Get rights and content

Abstract

The major function of mitochondria in human cells is to provide ATP by oxidative phosphorylation. However, mitochondria have many other roles including the modulation of intracellular calcium concentration and the regulation of apoptotic cell death. Furthermore, the mitochondrial respiratory chain is a major source of damaging free radicals. Consequently, mitochondrial dysfunction contributes to a number of human diseases, ranging from neurodegenerative diseases and ischaemia–reperfusion injury to obesity and diabetes. In addition, mutations to nuclear or mitochondrial DNA cause a number of human diseases. Therefore, strategies to prevent mitochondrial damage or to manipulate mitochondrial function in clinically useful ways may provide new therapies for a range of human disorders. Here we outline why mitochondria are a potentially important target for drug delivery and discuss how to deliver bioactive molecules selectively to mitochondria within cells.

Introduction

The effectiveness of any drug or gene therapy depends on delivering a bioactive molecule to the correct organ and cell type, and also on targeting it to the appropriate location within the cell [1]. Delivering biologically-active molecules to the appropriate intracellular compartment should not only increase their effectiveness and minimise side effects, but also enable cellular metabolism to be manipulated in increasingly specific ways. Mitochondria are a promising intracellular target for drug delivery [2], because damage to this organelle contributes to a range of human disorders and because mitochondrial function is important in apoptosis, oxidative damage, calcium metabolism, diabetes and obesity [3]. Furthermore, biologically active molecules can be delivered selectively to the organelle [2]. In this review we outline why mitochondria are a promising target for drug delivery and discuss how to deliver molecules selectively to the organelle.

Section snippets

Properties of mitochondria relevant to drug targeting and gene therapy

Most human cells contain substantial numbers of mitochondria in their cytoplasm whose principal function is ATP synthesis by oxidative phosphorylation [4], [5]. Mitochondria make ATP by passing electrons derived from the oxidation of food down the respiratory chain to react with oxygen, using the redox energy to translocate protons across the mitochondrial inner membrane [4], [5]. This establishes a proton electrochemical potential gradient across the inner membrane comprising a membrane

Why target drugs to mitochondria?

Here we outline how mitochondria contribute to human diseases to illustrate why delivery of drugs or bioactive molecules to mitochondria may be therapeutically useful.

How can molecules be targeted to mitochondria?

If the goals outlined above for mitochondrial medicine are to be achieved, it is essential to be able to selectively target drugs and biologically active molecules to mitochondria within cells in living organisms. Two properties of mitochondria may facilitate this: the large membrane potential across the inner membrane and the organelle’s protein import machinery. In this section we outline how these can be used to deliver molecules to mitochondria.

Problems and possibilities

Lipophilic cations have been used to deliver antioxidants or toxins to mitochondria within cells and this approach can be extended in many ways, for example to deliver other protective molecules such as iron or calcium chelators. Furthermore, by attaching molecules of known biological or pharmacological function to lipophilic cations it should be possible to manipulate mitochondrial function rationally. While there are many possible uses for such an approach, the repair or prevention of

Conclusion

Mitochondrial dysfunction is central to a range of important human disorders. If these diseases area to be treated and mitochondrial medicine is to develop, we need to be able to manipulate mitochondrial function and protect against mitochondrial damage in rational ways. This requires the selective delivery of bioactive compounds to mitochondria. Strategies utilising the mitochondrial membrane potential through lipophilic cations, or exploiting the mitochondrial protein import machinery may be

Acknowledgements

Work in the authors’ laboratories is supported by grants from the Marsden Fund, administered by the Royal Society of NZ, the Health Research Council of NZ, the Neurological Foundation of NZ and the Lottery Health Grants Committee.

References (174)

M.P Murphy
Targeting bioactive compounds to mitochondria
Trends Biotechnol.
(1997)
F Palmieri et al.
Mitochondrial metabolite transporters
Biochim. Biophys. Acta
(1996)
G Schatz
The protein import system of mitochondria
J. Biol. Chem.
(1996)
G Lenaz
Role of mitochondria in oxidative stress and ageing
Biochim. Biophys. Acta
(1998)
M.P Murphy et al.
Peroxynitrite: a biologically significant oxidant
Gen. Pharmacol.
(1998)
B.N Ames et al.
Mitochondrial decay in aging
Biochim. Biophys. Acta
(1995)
M Zoratti et al.
The mitochondrial permeability transition
Biochim. Biophys. Acta
(1995)
A.P Halestrap et al.
Elucidating the molecular mechanism of the permeability transition pore and its role in reperfusion injury
Biochim. Biophys. Acta
(1998)
J.J Lemasters et al.
The mitochondrial permeability transition in cell death: a common mechanism in necrosis, apoptosis and autophagy
Biochim. Biophys. Acta
(1998)
A.P Halestrap et al.
Oxidative stress, thiol reagents and membrane potential modulate the mitochondrial permeability transition by affecting nucleotide binding to the adenine nucleotide carrier
J. Biol. Chem.
(1997)

G Kroemer et al.

Mitochondrial control of apoptosis

Immunol. Today

(1997)

A.H Wyllie et al.

Cell death: The significance of apoptosis

Int. Rev. Cytol.

(1980)

M Leist et al.

Apoptosis, excitotoxicity, and neuropathology

Exp. Cell Res.

(1998)

M Leist et al.

The shape of cell death

Biochem. Biophys. Res. Commun.

(1997)

G.S Salvesen et al.

Caspases: intracellular signalling by proteolysis

Cell

(1997)

D.W Nicholson et al.

Caspases: Killer proteases

Trends Biochem. Sci.

(1997)

P Li et al.

Cytochrome c and dATP-dependent formation of Apaf-1/Caspase-9 complex initiates an apoptotic protease cascade

Cell

(1997)

H Zou et al.

Apaf-1, a human protein homologous to C. elegans CED-4, participates in Cytochrome c-dependent activation of caspase-3

Cell

(1997)

M.G Vander Heiden et al.

Bcl-X_L regulates the membrane potential and volume homeostasis of mitochondria

Cell

(1997)

J.C Reed et al.

Bcl-2 family proteins and mitochondria

Biochim. Biophys. Acta

(1998)

X Luo et al.

Bid, a Bcl2 interacting protein, mediates cytochrome c release from mitochondria in response to activation of cell surface death receptors

Cell

(1998)

J.L Scarlett et al.

Release of apoptogenic proteins from the mitochondrial intermembrane space during the mitochondrial permeability transition

FEBS Lett.

(1997)

D.F Babcock et al.

Mitochondrial oversight of cellular calcium signalling

Curr. Opin. Neurobiol.

(1998)

L.D Robb-Gaspers et al.

Coupling between cytosolic and mitochondrial calcium oscillations: role in the regulation of hepatic metabolism

Biochim. Biophys. Acta

(1998)

F Ichas et al.

From calcium signalling to cell death: two conformations for the mitochondrial permeability transition pore. Switching from low- to high-conductance state

Biochim. Biophys. Acta

(1998)

F Ichas et al.

Mitochondria are excitable organelles capable of generating and conveying electrical and calcium signals

Cell

(1997)

Y.-H Wei

Mitochondrial DNA alterations as ageing associated molecular events

Mutat. Res.

(1992)

M Corral-Debrinski et al.

Association of mitochondrial DNA damage with ageing and coronary atherosclerotic disease

Mutat. Res.

(1992)

G Solanes et al.

The human uncoupling protein-3 gene

J. Biol. Chem.

(1997)

O Boss et al.

Uncoupling protein 3: a new member of the mitochondrial carrier family with tissue-specific expression

FEBS Lett.

(1997)

W Mao et al.

UCP4, a novel brain-specific mitochondrial protein that reduces membrane potential in mammalian cells

FEBS Lett.

(1999)

P Ghafourifar et al.

Nitric oxide synthase activity in mitochondria

FEBS Lett.

(1997)

A Tatoyan et al.

Purification and characterization of a nitric-oxide synthase from rat liver mitochondria

J. Biol. Chem.

(1998)

G.C Brown

Nitric oxide regulates mitochondrial respiration and cell functions by inhibiting cytochrome oxidase

FEBS Lett.

(1995)

M.P Murphy

Slip and leak in mitochondrial oxidative phosphorylation

Biochim. Biophys. Acta

(1989)

G.F Azzone et al.

Determination of the proton electrochemical gradient across biological membranes

Curr. Top. Bioenerg.

(1984)

R Langer

Drug delivery and targeting

Nature

(1998)

D.C Wallace

Mitochondrial diseases in man and mouse

Science

(1999)

M Saraste

Oxidative phosphorylation at the fin de siecle

Science

(1999)

D.G Nicholls et al.

Bioenergetics 2

(1992)

D Tyler

The Mitochondrion in Health and Disease

(1992)

W Neupert

Protein import into mitochondria

Annu. Rev. Biochem.

(1997)

D.C Wallace

Mitochondrial DNA variation in human evolution, degenerative disease and aging

Am. J. Hum. Genet.

(1995)

M.P Yaffe

The machinery of mitochondrial inheritance and behavior

Science

(1999)

R Rizzuto et al.

Close contacts with the endoplasmic reticulum as determinants of mitochondrial Ca²⁺ responses

Science

(1998)

B Chance et al.

Hydroperoxide metabolism in mammalian organs

Physiol. Rev.

(1979)

K.B Beckman et al.

The free radical theory of aging matures

Physiol. Rev.

(1998)

M.K Shigenaga et al.

Oxidative damage and mitochondrial decay in aging

Proc. Natl. Acad. Sci. USA

(1994)

J.S Beckman et al.

Apparent hydroxyl radical production by peroxynitrite: implications for endothelial injury from nitric oxide and superoxide

Proc. Natl. Acad. Sci. USA

(1990)

C Richter et al.

Normal oxidative damage to mitochondrial and nuclear DNA is extensive

Proc. Natl. Acad. Sci. USA

(1988)

Cited by (397)

Mitochondria-targeted esculetin and metformin delay endothelial senescence by promoting fatty acid β-oxidation: Relevance in age-associated atherosclerosis
2024, Mechanisms of Ageing and Development
Impaired mitochondrial fatty acid β-oxidation (FAO) plays a role in the onset of several age-associated diseases, including atherosclerosis. In the current work, we investigated the efficacies of mitochondria-targeted esculetin (Mito-Esc) and metformin in enhancing FAO in human aortic endothelial cells (HAECs), and its relevance in the delay of cellular senescence and age-associated atherosclerotic plaque formation in Apoe^-/- mice. Chronic culturing of HAECs with either Mito-Esc or metformin increased oxygen consumption rates (OCR), and caused delay in senescence features. Conversely, etomoxir (CPT1 inhibitor) reversed Mito-Esc- and metformin-induced OCR, and caused premature endothelial senescence. Interestingly, Mito-Esc, unlike metformin, in the presence of etomoxir failed to preserve OCR. Thereby, underscoring Mito-Esc’s exclusive reliance on FAO as an energy source. Mechanistically, chronic culturing of HAECs with either Mito-Esc or metformin led to AMPK activation, increased CPT1 activity, and acetyl-CoA levels along with a concomitant reduction in malonyl-CoA levels, and lipid accumulation. Similar results were observed in Apoe^-/- mice aorta and liver tissue with a parallel reduction in age-associated atherosclerotic plaque formation and degeneration of liver with either Mito-Esc or metformin administration. Together, Mito-Esc and metformin by potentiating FAO, may have a role in the delay of cellular senescence by modulating mitochondrial function.
MitoQ protects against carbon tetrachloride-induced hepatocyte ferroptosis and acute liver injury by suppressing mtROS-mediated ACSL4 upregulation
2024, Toxicology and Applied Pharmacology
Ferroptosis has been shown to be involved in carbon tetrachloride (CCl₄)-induced acute liver injury (ALI). The mitochondrion-targeted antioxidant MitoQ can eliminate the production of mitochondrial reactive oxygen species (mtROS). This study investigated the role of MitoQ in CCl₄-induced hepatocytic ferroptosis and ALI. MDA and 4HNE were elevated in CCl₄-induced mice. In vitro, CCl₄ exposure elevated the levels of oxidized lipids in HepG2 cells. Alterations in the mitochondrial ultrastructure of hepatocytes were observed in the livers of CCl₄-evoked mice. Ferrostatin-1 (Fer-1) attenuated CCl₄-induced hepatic lipid peroxidation, mitochondrial ultrastructure alterations and ALI. Mechanistically, acyl-CoA synthetase long-chain family member 4 (ACSL4) was upregulated in CCl₄-exposed human hepatocytes and mouse livers. The ACSL4 inhibitor rosiglitazone alleviated CCl₄-induced hepatic lipid peroxidation and ALI. ACSL4 knockdown inhibited oxidized lipids in CCl₄-exposed human hepatocytes. Moreover, CCl₄ exposure decreased the mitochondrial membrane potential and OXPHOS subunit levels and increased the mtROS level in HepG2 cells. Correspondingly, MitoQ pretreatment inhibited the upregulation of ACSL4 in CCl₄-evoked mouse livers and HepG2 cells. MitoQ attenuated lipid peroxidation in vivo and in vitro after CCl₄ exposure. Finally, MitoQ pretreatment alleviated CCl₄-induced hepatocytic ferroptosis and ALI. These findings suggest that MitoQ protects against hepatocyte ferroptosis in CCl₄-induced ALI via the mtROS-ACSL4 pathway.
Revolutionizing cellular energy: The convergence of mitochondrial dynamics and delivery technologies
2024, Mitochondrion
The intersection of mitochondrial dynamics and delivery technologies heralds a paradigm shift in cellular biology and therapeutic intervention. Mitochondrial dynamics, encompassing fusion, fission, transport, and mitophagy, are critical for cellular energy production, signaling, and homeostasis. Dysregulation of these processes is implicated in a myriad of diseases, including neurodegenerative disorders, cardiovascular diseases, and cancer. Concurrently, advances in delivery technologies, such as nanocarriers, targeted delivery systems, and gene editing tools, offer unprecedented opportunities to manipulate mitochondrial function directly. This review synthesizes current knowledge on mitochondrial dynamics, examines recent breakthroughs in targeted delivery methods, and explores their potential convergence to modulate cellular energetics for therapeutic purposes. By integrating insights from biology, chemistry, and bioengineering, this review highlights the innovative approaches being developed to enhance mitochondrial function, underscoring the potential of this convergence to address complex diseases. This interdisciplinary perspective not only broadens our understanding of cellular processes but also paves the way for novel therapeutic strategies, marking a significant step forward in the quest for precision medicine and targeted interventions in mitochondrial-related diseases.
Performance of TMRM and Mitotrackers in mitochondrial morphofunctional analysis of primary human skin fibroblasts
2024, Biochimica et Biophysica Acta - Bioenergetics
Mitochondrial membrane potential (Δψ) and morphology are considered key readouts of mitochondrial functional state. This morphofunction can be studied using fluorescent dyes (“probes”) like tetramethylrhodamine methyl ester (TMRM) and Mitotrackers (MTs). Although these dyes are broadly used, information comparing their performance in mitochondrial morphology quantification and Δψ-sensitivity in the same cell model is still scarce. Here we applied epifluorescence microscopy of primary human skin fibroblasts to evaluate TMRM, Mitotracker Red CMXros (CMXros), Mitotracker Red CMH₂Xros (CMH2Xros), Mitotracker Green FM (MG) and Mitotracker Deep Red FM (MDR). All probes were suited for automated quantification of mitochondrial morphology parameters when Δψ was normal, although they did not deliver quantitatively identical results. The mitochondrial localization of TMRM and MTs was differentially sensitive to carbonyl cyanide-4-phenylhydrazone (FCCP)-induced Δψ depolarization, decreasing in the order: TMRM ≫ CHM2Xros = CMXros = MDR > MG. To study the effect of reversible Δψ changes, the impact of photo-induced Δψ “flickering” was studied in cells co-stained with TMRM and MG. During a flickering event, individual mitochondria displayed subsequent TMRM release and uptake, whereas this phenomenon was not observed for MG. Spatiotemporal and computational analysis of the flickering event provided evidence that TMRM redistributes between adjacent mitochondria by a mechanism dependent on Δψ and TMRM concentration. In summary, this study demonstrates that: (1) TMRM and MTs are suited for automated mitochondrial morphology quantification, (2) numerical data obtained with different probes is not identical, and (3) all probes are sensitive to FCCP-induced Δψ depolarization, with TMRM and MG displaying the highest and lowest sensitivity, respectively. We conclude that TMRM is better suited for integrated analysis of Δψ and mitochondrial morphology than the tested MTs under conditions that Δψ is not substantially depolarized.
Therapeutic efficacy of mitochondria-targeted esculetin in the improvement of NAFLD-NASH via modulating AMPK-SIRT1 axis
2023, International Immunopharmacology
Mitochondrial dysfunction due to deregulated production of mitochondria-derived ROS is implicated in the development and progression of non-alcoholic fatty liver disease (NAFLD) to non-alcoholic steatohepatitis (NASH). Recently, we synthesized a novel mitochondria-targeted esculetin (Mito-Esc) and investigated its dose–response therapeutic efficacy in mitigating high-fat diet (HFD)-induced NAFLD and NASH in Apoe^-/- mice. Mito-Esc administration, compared to simvastatin and pioglitazone, dose-dependently caused a significant reduction in body weight, improved lipid profile, glucose homeostasis, and pro-inflammatory cytokines level. Mito-Esc administration reduced adipose tissue hypertrophy and lipid accumulation presumably by regulating the levels of CD36, PPAR-γ, EBP-α, and their target genes. Mechanistically, Mito-Esc-induced activation of the AMPK1α-SIRT1 axis inhibited pre-adipocyte differentiation. Conversely, Mito-Esc failed to regulate pre-adipocyte differentiation under AMPK/SIRT1 depleted conditions. In parallel, Mito-Esc administration ameliorated HFD-induced steatosis, fibrosis of the liver, and NAFLD-associated atheromatous plaque formation in the aorta. Importantly, Mito-Esc administration inhibited HFD-induced infiltration of macrophages, a marker of steatohepatitis, in the adipose and liver tissues. The results of the in vitro studies showed that Mito-Esc treatment significantly inhibits TGF-β-induced hepatic stellate cell differentiation as well as the fibrotic markers. Consistent with the above observations, Mito-Esc treatment by activating the AMPK-SIRT1 pathway markedly reversed palmitate-induced mitochondrial superoxide production, depolarization of mitochondrial membrane potential, and lipid accumulation in HepG2 cells. Together, the therapeutic efficacy of Mito-Esc in the mitigation of HFD-induced lipotoxicity, and the associated NASH is in part, mediated by potentiating the AMPK-SIRT1 axis.
When near-infrared fluorescence meets supramolecular coordination complexes: Challenges and opportunities of metallacycles/metallacages in precision biomedicine
2023, Coordination Chemistry Reviews
In the past decade, the metallacycles/metallacages have attracted unremitting interest in biomedical fields, yet visual tracking of their in vivo delivery, targeting ability, biodistribution and therapeutic evaluation are still hampered by their short emission wavelengths. More recently, the near-infrared biochannel (NIR, 0.7–1.7 μm) especially the NIR-II region (1.0–1.7 μm) provides deeper tissue penetration and higher contrast than traditional UV–Vis region for in vivo imaging. In this context, we provide a comprehensive and systematic insight into the development of NIR metallacycles/metallacages for biomedical applications. Finally, we also discuss the challenges and prospects of NIR metallacycles/metallacages for future biomedical research and clinical translation.

View all citing articles on Scopus

View full text

Drug delivery to mitochondria: the key to mitochondrial medicine

Abstract

Introduction

Section snippets

Properties of mitochondria relevant to drug targeting and gene therapy

Why target drugs to mitochondria?

How can molecules be targeted to mitochondria?

Problems and possibilities

Conclusion

Acknowledgements

Trends Biotechnol.

Biochim. Biophys. Acta

J. Biol. Chem.

Biochim. Biophys. Acta

Gen. Pharmacol.

Biochim. Biophys. Acta

Biochim. Biophys. Acta

Biochim. Biophys. Acta

Biochim. Biophys. Acta

J. Biol. Chem.

Immunol. Today

Int. Rev. Cytol.

Exp. Cell Res.

Biochem. Biophys. Res. Commun.

Cell

Trends Biochem. Sci.

Cell

Cell

Cell

Biochim. Biophys. Acta

Cell

FEBS Lett.

Curr. Opin. Neurobiol.

Biochim. Biophys. Acta

Biochim. Biophys. Acta

Cell

Mutat. Res.

Mutat. Res.

J. Biol. Chem.

FEBS Lett.

FEBS Lett.

FEBS Lett.

J. Biol. Chem.

FEBS Lett.

Biochim. Biophys. Acta

Curr. Top. Bioenerg.

Drug delivery and targeting

Nature

Mitochondrial diseases in man and mouse

Science

Oxidative phosphorylation at the fin de siecle

Science

Bioenergetics 2

The Mitochondrion in Health and Disease

Protein import into mitochondria

Annu. Rev. Biochem.

Mitochondrial DNA variation in human evolution, degenerative disease and aging

Am. J. Hum. Genet.

The machinery of mitochondrial inheritance and behavior

Science

Close contacts with the endoplasmic reticulum as determinants of mitochondrial Ca2+ responses

Science

Hydroperoxide metabolism in mammalian organs

Physiol. Rev.

The free radical theory of aging matures

Physiol. Rev.

Oxidative damage and mitochondrial decay in aging

Proc. Natl. Acad. Sci. USA

Apparent hydroxyl radical production by peroxynitrite: implications for endothelial injury from nitric oxide and superoxide

Proc. Natl. Acad. Sci. USA

Normal oxidative damage to mitochondrial and nuclear DNA is extensive

Proc. Natl. Acad. Sci. USA

Close contacts with the endoplasmic reticulum as determinants of mitochondrial Ca²⁺ responses