Cytotoxic oxysterols induce caspase-independent myelin figure formation and caspase-dependent polar lipid accumulation

L-kynurenine and quinolinic acid inhibited markers of cell survival in B16 F10 melanoma cells in vitro

Melanoma is an aggressive malignancy and remains a major cause of skin cancer mortality, highlighting the need for new treatment strategies. Recent findings revealed that L-kynurenine and quinolinic acid induce cytotoxicity and morphological changes in B16 F10 melanoma cells in vitro. This paper highlights the effects of L-kynurenine and quinolinic acid at previously determined half-maximal inhibitory concentrations on cell cycle progression, cell death and extracellular signal-regulated protein kinase inhibition. Melanoma, B16 F10 and murine macrophages, RAW 264.7 cells were used in this study, as both cell lines express all the enzymes associated with the kynurenine pathway. Post exposure to the compounds at half-maximal inhibitory concentrations, transmission electron microscopy was used to assess intracellular morphological changes. Flow cytometry was used to analyse cell cycle progression and quantify apoptosis via the dual staining of Annexin V and propidium iodide and cell survival via extracellular signal-regulated protein kinase. L-kynurenine and quinolinic acid at half-maximal inhibitory concentrations induced intracellular morphological changes representative of cell death. Flow cytometry revealed alterations in cell cycle distribution, increased apoptosis and significantly inhibition of cell survival. L-kynurenine and quinolinic acid are exogenous kynurenine compounds which inhibited cell survival through extracellular signal-regulated protein kinase inhibition, induced cell cycle alterations and induced apoptosis in B16 F10 melanoma cells.

The Cholesterol-5,6-Epoxide Hydrolase: A Metabolic Checkpoint in Several Diseases

Cholesterol-5,6-epoxides (5,6-ECs) are oxysterols (OS) that have been linked to several pathologies including cancers and neurodegenerative diseases. 5,6-ECs can be produced from cholesterol by several mechanisms including reactive oxygen species, lipoperoxidation, and cytochrome P450 enzymes. 5,6-ECs exist as two different diastereoisomers: 5,6α-EC and 5,6β-EC with different metabolic fates. They can be produced as a mixture or as single products of epoxidation. The epoxide ring of 5,6α-EC and 5,6β-EC is very stable and 5,6-ECs are prone to hydration by the cholesterol-5,6-epoxide hydrolase (ChEH) to give cholestane-3β,5α,6β-triol, which can be further oxidized into oncosterone. 5,6α-EC is prone to chemical and enzymatic conjugation reactions leading to bioactive compounds such as dendrogenins, highlighting the existence of a new metabolic branch on the cholesterol pathway centered on 5,6α-EC. We will summarize in this chapter current knowledge on this pathway which is controlled by the ChEH.

Impact of Oxysterols in Age-Related Disorders and Strategies to Alleviate Adverse Effects

Oxysterols or cholesterol oxidation products are a class of molecules with the sterol moiety, derived from oxidative reaction of cholesterol through enzymatic and non-enzymatic processes. They are widely reported in animal-origin foods and prove significant involvement in the regulation of cholesterol homeostasis, lipid transport, cellular signaling, and other physiological processes. Reports of oxysterol-mediated cytotoxicity are in abundance and thus consequently implicated in several age-related and lifestyle disorders such as cardiovascular diseases, bone disorders, pancreatic disorders, age-related macular degeneration, cataract, neurodegenerative disorders such as Alzheimer's and Parkinson's disease, and some types of cancers. In this chapter, we attempt to review a selection of physiologically relevant oxysterols, with a focus on their formation, properties, and roles in health and disease, while also delving into the potential of natural and synthetic molecules along with bacterial enzymes for mitigating oxysterol-mediated cell damage.

Attenuation of 7-ketocholesterol- and 7β-hydroxycholesterol-induced oxiapoptophagy by nutrients, synthetic molecules and oils: Potential for the prevention of age-related diseases

Age-related diseases for which there are no effective treatments include cardiovascular diseases; neurodegenerative diseases such as Alzheimer's disease; eye disorders such as cataract and age-related macular degeneration; and, more recently, Severe Acute Respiratory Syndrome (SARS-CoV-2). These diseases are associated with plasma and/or tissue increases in cholesterol derivatives mainly formed by auto-oxidation: 7-ketocholesterol, also known as 7-oxo-cholesterol, and 7β-hydroxycholesterol. The formation of these oxysterols can be considered as a consequence of mitochondrial and peroxisomal dysfunction, leading to increased in oxidative stress, which is accentuated with age. 7-ketocholesterol and 7β-hydroxycholesterol cause a specific form of cytotoxic activity defined as oxiapoptophagy, including oxidative stress and induction of death by apoptosis associated with autophagic criteria. Oxiaptophagy is associated with organelle dysfunction and in particular with mitochondrial and peroxisomal alterations involved in the induction of cell death and in the rupture of redox balance. As the criteria characterizing 7-ketocholesterol- and 7β-hydroxycholesterol-induced cytotoxicity are often simultaneously observed in major age-related diseases (cardiovascular diseases, age-related macular degeneration, Alzheimer's disease) the involvement of these oxysterols in the pathophysiology of the latter seems increasingly likely. It is therefore important to better understand the signalling pathways associated with the toxicity of 7-ketocholesterol and 7β-hydroxycholesterol in order to identify pharmacological targets, nutrients and synthetic molecules attenuating or inhibiting the cytotoxic activities of these oxysterols. Numerous natural cytoprotective compounds have been identified: vitamins, fatty acids, polyphenols, terpenes, vegetal pigments, antioxidants, mixtures of compounds (oils, plant extracts) and bacterial enzymes. However, few synthetic molecules are able to prevent 7-ketocholesterol- and/or 7β-hydroxycholesterol-induced cytotoxicity: dimethyl fumarate, monomethyl fumarate, the tyrosine kinase inhibitor AG126, memantine, simvastatine, Trolox, dimethylsufoxide, mangafodipir and mitochondrial permeability transition pore (MPTP) inhibitors. The effectiveness of these compounds, several of which are already in use in humans, makes it possible to consider using them for the treatment of certain age-related diseases associated with increased plasma and/or tissue levels of 7-ketocholesterol and/or 7β-hydroxycholesterol.

Role of pH level on the morphology and growth rate of myelin figures

The myelin figure (MF) is one of the basic structures of lipids, and the study of their formation and the effect of various parameters on their growth is useful in understanding several biological processes. In this paper, we address the influence of the pH degree of the surrounding medium on MF dynamics. We introduce a tunable shearing digital holographic microscopy arrangement to obtain quantitative and volumetric information about the complex growth of MFs. Our results show that (1) the time evolution of relative length and volume changes of MFs follows a power-law, (2) the acidity facilitates the growth rate, and (3) the acidic environment causes the formation of thicker MFs.

Localisation of oxysterols at the sub-cellular level and in biological fluids

Oxysterols are oxidized derivatives of cholesterol that are formed enzymatically or via reactive oxygen species or both. Cholesterol or oxysterols ingested as food are absorbed and packed into lipoproteins that are taken up by hepatic cells. Within hepatic cells, excess cholesterol is metabolised to form bile acids. The endoplasmic reticulum acts as the main organelle in the bile acid synthesis pathway. Metabolised sterols originating from this pathway are distributed within other organelles and in the cell membrane. The alterations to membrane oxysterol:sterol ratio affects the integrity of the cell membrane. The presence of oxysterols changes membrane fluidity and receptor orientation. It is well documented that hydroxylase enzymes located in mitochondria facilitate oxysterol production via an acidic pathway. More recently, the presence of oxysterols was also reported in lysosomes. Peroxisomal deficiencies favour intracellular oxysterols accumulation. Despite the low abundance of oxysterols compared to cholesterol, the biological actions of oxysterols are numerous and important. Oxysterol levels are implicated in the pathogenesis of multiple diseases ranging from chronic inflammatory diseases (atherosclerosis, Alzheimer's disease and bowel disease), cancer and numerous neurodegenerative diseases. In this article, we review the distribution of oxysterols in sub-cellular organelles and in biological fluids.

Dose-dependent cytotoxicity of bismuth nanoparticles produced by LASiS in a reference mammalian cell line BALB/c 3T3

Nanoparticles (NPs) have emerged as new potential tools for many applications in previous years. Among all types of NPs, bismuth NPs (BiNPs) have a very low cost and potential for many applications, ranging from medicine to industry. Although the toxic effects of bismuth have been studied, little is known about its toxicity at the nanoscale level. Therefore, in this study, we aimed to investigate the cytotoxic effects of BiNPs produced by laser ablation synthesis in solution (LASiS) in a reference mammalian cell line to evaluate their cytotoxicity (BALB/c 3 T3 cells). We also stabilized BiNPs in two different solutions: culture medium supplemented with fetal bovine serum (FBS) and bovine serum albumin (BSA). The cytotoxicity of BiNPs in culture medium (IC₅₀:28.51 ± 9.96 μg/ml) and in BSA (IC₅₀:25.54 ± 8.37 μg/ml) was assessed, and they were not significantly different. Second, the LD₅₀ was predicted, and BiNPs were estimated as GHS class 4. We also found that cell death occurs due to apoptosis. By evaluating the interaction between BiNPs and cells at ultrastructural level, we suggest that cell death occurs once BiNPs are internalized. Additionally, we suggest that BiNPs cause cell damage because myelin figures were found inside cells that had internalized BiNPs. To date, this is the first study to assess the cytotoxicity of BiNPs produced by LASiS and to predict the possible LD₅₀ and GHS class of BiNPs.

Esterification of 24S-OHC induces formation of atypical lipid droplet-like structures, leading to neuronal cell death

The 24(S)-hydroxycholesterol (24S-OHC), which plays an important role in maintaining brain cholesterol homeostasis, has been shown to possess neurotoxicity. We have previously reported that 24S-OHC esterification by ACAT1 and the resulting lipid droplet (LD) formation are responsible for 24S-OHC-induced cell death. In the present study, we investigate the functional roles of 24S-OHC esters and LD formation in 24S-OHC-induced cell death, and we identify four long-chain unsaturated fatty acids (oleic acid, linoleic acid, arachidonic acid, and DHA) with which 24S-OHC is esterified in human neuroblastoma SH-SY5Y cells treated with 24S-OHC. Here, we find that cotreatment of cells with 24S-OHC and each of these four unsaturated fatty acids increases prevalence of the corresponding 24S-OHC ester and exacerbates induction of cell death as compared with cell death induced by treatment with 24S-OHC alone. Using electron microscopy, we find in the present study that 24S-OHC induces formation of LD-like structures coupled with enlarged endoplasmic reticulum (ER) lumina, and that these effects are suppressed by treatment with ACAT inhibitor. Collectively, these results illustrate that ACAT1-catalyzed esterification of 24S-OHC with long-chain unsaturated fatty acid followed by formation of atypical LD-like structures at the ER membrane is a critical requirement for 24S-OHC-induced cell death.

Amyloidosis, inflammation, and oxidative stress in the heart of an alkaptonuric patient

Background. Alkaptonuria, a rare autosomal recessive metabolic disorder caused by deficiency in homogentisate 1,2-dioxygenase activity, leads to accumulation of oxidised homogentisic acid in cartilage and collagenous structures present in all organs and tissues, especially joints and heart, causing a pigmentation called ochronosis. A secondary amyloidosis is associated with AKU. Here we report a study of an aortic valve from an AKU patient. Results. Congo Red birefringence, Th-T fluorescence, and biochemical assays demonstrated the presence of SAA-amyloid deposits in AKU stenotic aortic valve. Light and electron microscopy assessed the colocalization of ochronotic pigment and SAA-amyloid, the presence of calcified areas in the valve. Immunofluorescence detected lipid peroxidation of the tissue and lymphocyte/macrophage infiltration causing inflammation. High SAA plasma levels and proinflammatory cytokines levels comparable to those from rheumatoid arthritis patients were found in AKU patient. Conclusions. SAA-amyloidosis was present in the aortic valve from an AKU patient and colocalized with ochronotic pigment as well as with tissue calcification, lipid oxidation, macrophages infiltration, cell death, and tissue degeneration. A local HGD expression in human cardiac tissue has also been ascertained suggesting a consequent local production of ochronotic pigment in AKU heart.

High-resolution fluorescence microscopy of myelin without exogenous probes

Myelin is a critical element of the central and peripheral nervous systems of all higher vertebrates. Any disturbance in the integrity of the myelin sheath interferes with the axon's ability to conduct action potentials. Thus, the study of myelin structure and biochemistry is critically important. Accurate and even staining of myelin is often difficult because of its lipid-rich nature and multiple tight membrane wraps, hindering penetration of immunoprobes. Here we show a method of visualizing myelin that is fast, inexpensive and reliable using the cross-linking fixative glutaraldehyde that produces strong, broad-spectrum auto-fluorescence in fixed tissue. Traditionally, effort is generally aimed at eliminating this auto-fluorescence. However, we show that this intrinsic signal, which is very photostable and particularly strong in glutaraldehyde-fixed myelin, can be exploited to visualize this structure to produce very detailed images of myelin morphology. We imaged fixed rodent tissues from the central and peripheral nervous systems using spectral confocal microscopy to acquire high-resolution 3-dimensional images spanning the visual range of wavelengths (400-750 nm). Mathematical post-processing allows accurate and unequivocal separation of broadband auto-fluorescence from exogenous fluorescent probes such as DAPI and fluorescently-tagged secondary antibodies. We additionally show the feasibility of immunohistochemistry with antigen retrieval, which allows co-localization of proteins of interest together with detailed myelin morphology. The lysolecithin model of de- and remyelination is shown as an example of a practical application of this technique, which can be routinely applied when high-resolution microscopy of central or peripheral myelinated tracts is required.

Fodipir and its dephosphorylated derivative dipyridoxyl ethyldiamine are involved in mangafodipir-mediated cytoprotection against 7β-hydroxycholesterol-induced cell death

OBJECTIVE

Mangafodipir exerts pharmacological effects, including vascular relaxation and protection against oxidative stress and cell death induced by oxysterols. Additionally, mangafodipir has been proposed for cardiovascular imaging. The primary metabolites of mangafodipir, manganese dipyridoxyl ethyldiamine (MnPLED) and its constituent dipyridoxyl diphosphate (Dp-dp) also known as fodipir, are pharmacologically active. However, whether they affect oxysterol-induced cytotoxicity is currently unknown. In this study, we examine whether the mangafodipir metabolite affects 7β-hydroxycholesterol (7β-OH)-induced cell death and identify the underlying mechanisms.

METHODS

U937 cells were pretreated or not with mangafodipir substrate (Ms; 200 µm), MnPLED (100 µmol/l) or Dp-dp (100 µmol/l) for 8 h and then exposed to 7β-OH (28 µmol/l) for 18 h.

RESULTS

Our results revealed that pretreatment with MnPLED or Dp-dp protected against 7β-OH-induced cellular reactive oxygen species (ROS) production, apoptosis, and lysosomal membrane permeabilization (LMP). MnPLED and Dp-dp, in par with Ms, confer protection against 7β-OH-induced cytotoxicity by reducing cellular ROS and stabilization of the lysosomal membrane.

CONCLUSION

These results suggest that fodipir is the pharmacologically active part in the structure of mangafodipir, which prevents 7β-OH-induced cell death by attenuating cellular ROS and by preventing LMP. In addition, MnPLED, which is the dephosphorylated product of fodipir, exerts a similar protective effect against 7β-OH-induced cytotoxicity. This result indicates that dephosphorylation of fodipir does not affect its pharmacological actions. Altogether our result confirms the cytoprotective effect of mangafodipir and justifies its potential use as a cytoprotective adjuvant.

Anticancer steroids: linking natural and semi-synthetic compounds

Steroids, a widespread class of natural organic compounds occurring in animals, plants and fungi, have shown great therapeutic value for a broad array of pathologies. The present overview is focused on the anticancer activity of steroids, which is very representative of a rich structural molecular diversity and ability to interact with various biological targets and pathways. This review encompasses the most relevant discoveries on steroid anticancer drugs and leads through the last decade and comprises 668 references.

11β-Hydroxysteroid dehydrogenase type 1 contributes to the regulation of 7-oxysterol levels in the arterial wall through the inter-conversion of 7-ketocholesterol and 7β-hydroxycholesterol

The atherogenic 7-oxysterols, 7-ketocholesterol (7-KC) and 7β-hydroxycholesterol (7βOHC), can directly impair arterial function. Inter-conversion of 7-KC and 7βOHC has recently been shown as a novel role for the glucocorticoid-metabolizing enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). Since this enzyme is expressed in vascular smooth muscle cells, we addressed the hypothesis that inter-conversion of 7-KC and 7βOHC by 11β-HSD1 may contribute to regulation of arterial function.

Incubation (4–24 h) of aortic rings with either 7-KC (25 μM) or 7βOHC (20 μM) had no effect on endothelium-dependent (acetylcholine) or -independent (sodium nitroprusside) relaxation. In contrast, exposure to 7-KC (but not to 7βOHC) attenuated noradrenaline-induced contraction (E_max) after 4 h (0.78 ± 0.28 vs 0.40 ± 0.08 mN/mm; p < 0.05) and 24 h (2.28 ± 0.34 vs 1.56 ± 0.48 mN/mm; p < 0.05). Both 7-oxysterols were detected by GCMS in the aortic wall of chow-fed C57Bl6/J mice, with concentrations of 7-KC (1.41 ± 0.81 ng/mg) higher (p = 0.05) than 7βOHC (0.16 ± 0.06 ng/mg). In isolated mouse aortic rings 11β-HSD1 was shown to act as an oxo-reductase, inter-converting 7-KC and 7βOHC. This activity was lost in aorta from 11β-HSD1^−/− mice, which had low oxysterol levels. Renal homogenates from 11β-HSD1^−/− mice were used to confirm that the type 2 isozyme of 11β-HSD does not inter-convert 7-KC and 7βOHC.

These results demonstrate that 7-KC has greater effects than 7βOHC on vascular function, and that 11β-HSD1 can inter-convert 7-KC and 7βOHC in the arterial wall, contributing to the regulation of 7-oxysterol levels and potentially influencing vascular function. This mechanism may be important in the cardioprotective effects of 11β-HSD1 inhibitors.

Inflammation-related gene expression by lipid oxidation-derived products in the progression of atherosclerosis

Vascular areas of atherosclerotic development persist in a state of inflammation, and any further inflammatory stimulus in the subintimal area elicits a proatherogenic response; this alters the behavior of the artery wall cells and recruits further inflammatory cells. In association with the inflammatory response, oxidative events are also involved in the development of atherosclerotic plaques. It is now unanimously recognized that lipid oxidation-derived products are key players in the initiation and progression of atherosclerotic lesions. Oxidized lipids, derived from oxidatively modified low-density lipoproteins (LDLs), which accumulate in the intima, strongly modulate inflammation-related gene expression, through involvement of various signaling pathways. In addition, considerable evidence supports a proatherogenic role of a large group of potent bioactive lipids called eicosanoids, which derive from oxidation of arachidonic acid, a component of membrane phospholipids. Of note, LDL lipid oxidation products might regulate eicosanoid production, modulating the enzymatic degradation of arachidonic acid by cyclooxygenases and lipoxygenases; these enzymes might also directly contribute to LDL oxidation. This review provides a comprehensive overview of current knowledge on signal transduction pathways and inflammatory gene expression, modulated by lipid oxidation-derived products, in the progression of atherosclerosis.

Effects of oxysterols on cell viability, inflammatory cytokines, VEGF, and reactive oxygen species production on human retinal cells: cytoprotective effects and prevention of VEGF secretion by resveratrol

BACKGROUND AND AIMS

Oxysterols are assumed to play important roles in age-related macular degeneration, a major cause of blindness. So we characterized the cytotoxic, oxidative, inflammatory, and angiogenic activities of oxysterols (7β-hydroxycholesterol (7β-OH), 7-ketocholesterol (7KC), 25-hydroxycholesterol (25-OH)) in human retinal ARPE-19 cells, and evaluated the protective effects of resveratrol (Rsv: 1 μM), a polyphenol from red wine.

METHODS

ARPE-19 cells were treated with 7β-OH, 7KC, or 25-OH (5-40 μg/mL; 24-48 h) without or with Rsv. Cell viability was determined using trypan blue and the MTT assay. Cell death was characterized by electron microscopy and in situ detection of activated caspases with fluorochrome-labeled inhibitors of caspases. Reactive oxygen species (ROS) production was measured with hydroethidine. ELISA methods and a cytometric bead assay were used to quantify cytokines involved in inflammation (IL-8, IL-1β, IL-6, IL-10, IL-12p70, TNF-α, MCP-1) and VEGF.

RESULTS

7β-OH and 7KC triggered a caspase-independent cell death process associated with the presence of multilamellar cytoplasmic structures evocating phospholipidosis, increased ROS production, and IL-8 secretion. 7β-OH enhanced VEGF secretion. No cytotoxic effects were identified with 25-OH, which highly stimulated ROS production, MCP-1, and VEGF secretion. With oxysterols, no IL-10, TNF-α, and IL-12p70 secretion were detected. 25-OH induced IL-8 secretion through the MEK/ERK½ signaling pathway, and Rsv showed cytoprotective activities and inhibited VEGF secretion.

CONCLUSION

7β-OH, 7KC, and 25-OH have cytotoxic, oxidative, inflammatory, and/or angiogenic activities on ARPE-19 cells. As Rsv has some protective effects against oxysterol-induced cell death and VEGF secretion it could be valuable in ARMD treatment.

Mammalian epoxide hydrolases in xenobiotic metabolism and signalling

Epoxide hydrolases catalyse the hydrolysis of electrophilic--and therefore potentially genotoxic--epoxides to the corresponding less reactive vicinal diols, which explains the classification of epoxide hydrolases as typical detoxifying enzymes. The best example is mammalian microsomal epoxide hydrolase (mEH)-an enzyme prone to detoxification-due to a high expression level in the liver, a broad substrate selectivity, as well as inducibility by foreign compounds. The mEH is capable of inactivating a large number of structurally different, highly reactive epoxides and hence is an important part of the enzymatic defence of our organism against adverse effects of foreign compounds. Furthermore, evidence is accumulating that mammalian epoxide hydrolases play physiological roles other than detoxification, particularly through involvement in signalling processes. This certainly holds true for soluble epoxide hydrolase (sEH) whose main function seems to be the turnover of lipid derived epoxides, which are signalling lipids with diverse functions in regulatory processes, such as control of blood pressure, inflammatory processes, cell proliferation and nociception. In recent years, the sEH has attracted attention as a promising target for pharmacological inhibition to treat hypertension and possibly other diseases. Recently, new hitherto uncharacterised epoxide hydrolases could be identified in mammals by genome analysis. The expression pattern and substrate selectivity of these new epoxide hydrolases suggests their participation in signalling processes rather than a role in detoxification. Taken together, epoxide hydrolases (1) play a central role in the detoxification of genotoxic epoxides and (2) have an important function in the regulation of physiological processes by the control of signalling molecules with an epoxide structure.

State-of-the-art technologies, current opinions and developments, and novel findings: news from the field of histochemistry and cell biology

Investigations of cell and tissue structure and function using innovative methods and approaches have again yielded numerous exciting findings in recent months and have added important data to current knowledge, inspiring new ideas and hypotheses in various fields of modern life sciences. Topics and contents of comprehensive expert reviews covering different aspects in methodological advances, cell biology, tissue function and morphology, and novel findings reported in original papers are summarized in the present review.

Involvement of Fas signalling in 7beta-hydroxycholesterol-and cholesterol-5beta,6beta-epoxide-induced apoptosis

The induction of apoptosis in cells of the arterial wall is a critical event in the development of atheroma. 7beta-Hydroxycholesterol (7beta-OH) and cholesterol-5beta,6beta-epoxide (beta-epoxide) are components of oxLDL and have previously been shown to be potent inducers of apoptosis. However, the exact mechanisms through which these oxysterols induce apoptosis remains to be fully elucidated. The specific interaction of the Fas death receptor with Fas ligand (FasL) initiates a caspase cascade culminating in apoptosis. The purpose of the present study was to determine the involvement of Fas signalling in 7beta-OH-and beta-epoxide-induced apoptosis. To this end we employed the Fas/FasL antagonist, Kp7-6, and examined the effect of Fas inhibition on oxysterol-induced cell death in U937 cells. Fas levels were increased following 24 h exposure to 30 micro M 7beta-OH while treatment with 30 micro M beta-epoxide had no effect. Kp7-6 reduced the Fas content of 7beta-OH-treated cells to control levels and partially protected against 7beta-OH-induced apoptosis. This coincided with a decrease in cytochrome c release along with a reduction in caspase-3 and caspase-8 activity. Our data implicate Fas signalling in the apoptotic pathway induced by 7beta-OH and also highlight differences between apoptosis induced by 7beta-OH and beta-epoxide.

Recent progress in histochemistry

The progress in discerning the structure and function of cells and tissues in health and disease has been achieved to a large extent by the continued development of new reagents for histochemistry, the improvement of existing techniques and new imaging techniques. This review will highlight some advancements made in these fields.