The mitochondrial succinate dehydrogenase complex controls the STAT3-IL-10 pathway in inflammatory macrophages.

The functions of macrophages are tightly regulated by their metabolic state. However, the role of the mitochondrial electron transport chain (ETC) in macrophage functions remains understudied. Here, we provide evidence that the succinate dehydrogenase (SDH)/complex II (CII) is required for respiration and plays a role in controlling effector responses in macrophages. We find that the absence of the catalytic subunits Sdha and Sdhb in macrophages impairs their ability to effectively stabilize HIF-1α and produce the pro-inflammatory cytokine IL-1ß in response to LPS stimulation. We also arrive at the novel result that both subunits are essential for the LPS-driven production of IL-10, a potent negative feedback regulator of the macrophage inflammatory response. This phenomenon is explained by the fact that the absence of Sdha and Sdhb leads to the inhibition of Stat3 tyrosine phosphorylation, caused partially by the excessive accumulation of mitochondrial reactive oxygen species (mitoROS) in the knockout cells.

Characterization of endogenous Kv1.3 channel isoforms in T cells.

Voltage-dependent potassium channel Kv1.3 plays a key role on T-cell activation; however, lack of reliable antibodies has prevented its accurate detection under endogenous circumstances. To overcome this limitation, we created a Jurkat T-cell line with endogenous Kv1.3 channel tagged, to determine the expression, location, and changes upon activation of the native Kv1.3 channels. CRISPR-Cas9 technique was used to insert a Flag-Myc peptide at the C terminus of the KCNA3 gene. Basal or activated channel expression was studied using western blot analysis and imaging techniques. We identified two isoforms of Kv1.3 other than the canonical channel (54 KDa) differing on their N terminus: a longer isoform (70 KDa) and a truncated isoform (43 KDa). All three isoforms were upregulated after T-cell activation. We focused on the functional characterization of the truncated isoform (short form, SF), because it has not been previously described and could be present in the available Kv1.3-/- mice models. Overexpression of SF in HEK cells elicited small amplitude Kv1.3-like currents, which, contrary to canonical Kv1.3, did not induce HEK proliferation. To explore the role of endogenous SF isoform in a native system, we generated both a knockout Jurkat clone and a clone expressing only the SF isoform. Although the canonical isoform (long form) localizes mainly at the plasma membrane, SF remains intracellular, accumulating perinuclearly. Accordingly, SF Jurkat cells did not show Kv1.3 currents and exhibited depolarized resting membrane potential (VM ), decreased Ca2+ influx, and a reduction in the [Ca2+ ]i increase upon stimulation. Functional characterization of these Kv1.3 channel isoforms showed their differential contribution to signaling pathways involved in formation of the immunological synapse. We conclude that alternative translation initiation generates at least three endogenous Kv1.3 channel isoforms in T cells that exhibit different functional roles. For some of these functions, Kv1.3 proteins do not need to form functional plasma membrane channels.

miR-126 contributes to the epigenetic signature of diabetic vascular smooth muscle and enhances antirestenosis effects of Kv1.3 blockers.

OBJECTIVES: Restenosis after vessel angioplasty due to dedifferentiation of the vascular smooth muscle cells (VSMCs) limits the success of surgical treatment of vascular occlusions. Type 2 diabetes (T2DM) has a major impact on restenosis, with patients exhibiting more aggressive forms of vascular disease and poorer outcomes after surgery. Kv1.3 channels are critical players in VSMC proliferation. Kv1.3 blockers inhibit VSMCs MEK/ERK signalling and prevent vessel restenosis. We hypothesize that dysregulation of microRNAs (miR) play critical roles in adverse remodelling, contributing to Kv1.3 blockers efficacy in T2DM VSMCs. METHODS AND RESULTS: We used clinically relevant in vivo models of vascular risk factors (VRF) and vessels and VSMCs from T2DM patients. RESUKTS: Human T2DM vessels showed increased remodelling, and changes persisted in culture, with augmented VSMCs migration and proliferation. Moreover, there were downregulation of PI3K/AKT/mTOR and upregulation of MEK/ERK pathways, with increased miR-126 expression. The inhibitory effects of Kv1.3 blockers on remodelling were significantly enhanced in T2DM VSMCs and in VRF model. Finally, miR-126 overexpression confered "diabetic" phenotype to non-T2DM VSMCs by downregulating PI3K/AKT axis. CONCLUSIONS: miR-126 plays crucial roles in T2DM VSMC metabolic memory through activation of MEK/ERK pathway, enhancing the efficacy of Kv1.3 blockers in the prevention of restenosis in T2DM patients.

Voltage-dependent conformational changes of Kv1.3 channels activate cell proliferation.

The voltage-dependent potassium channel Kv1.3 has been implicated in proliferation in many cell types, based on the observation that Kv1.3 blockers inhibited proliferation. By modulating membrane potential, cell volume, and/or Ca2+ influx, K+  channels can influence cell cycle progression. Also, noncanonical channel functions could contribute to modulate cell proliferation independent of K+ efflux. The specificity of the requirement of Kv1.3 channels for proliferation suggests the involvement of molecule-specific interactions, but the underlying mechanisms are poorly identified. Heterologous expression of Kv1.3 channels in HEK cells has been shown to increase proliferation independently of K+ fluxes. Likewise, some of the molecular determinants of Kv1.3-induced proliferation have been located in the C-terminus region, where individual point mutations of putative phosphorylation sites (Y447A and S459A) abolished Kv1.3-induced proliferation. Here, we investigated the mechanisms linking Kv1.3 channels to proliferation exploring the correlation between Kv1.3 voltage-dependent molecular dynamics and cell cycle progression. Using transfected HEK cells, we analyzed both the effect of changes in resting membrane potential on Kv1.3-induced proliferation and the effect of mutated Kv1.3 channels with altered voltage dependence of gating. We conclude that voltage-dependent transitions of Kv1.3 channels enable the activation of proliferative pathways. We also found that Kv1.3 associated with IQGAP3, a scaffold protein involved in proliferation, and that membrane depolarization facilitates their interaction. The functional contribution of Kv1.3-IQGAP3 interplay to cell proliferation was demonstrated both in HEK cells and in vascular smooth muscle cells. Our data indicate that voltage-dependent conformational changes of Kv1.3 are an essential element in Kv1.3-induced proliferation.

Elastin-like recombinamer-based devices releasing Kv1.3 blockers for the prevention of intimal hyperplasia: An in vitro and in vivo study.

Coronary artery disease (CAD) is the most common cardiovascular disorder. Vascular surgery strategies for coronary revascularization (either percutaneous or open) show a high rate of failure because of restenosis of the vessel, due to phenotypic switch of vascular smooth muscle cells (VSMCs) leading to proliferation and migration. We have previously reported that the inhibition of Kv1.3 channel function with selective blockers represents an effective strategy for the prevention of restenosis in human vessels used for coronary angioplasty procedures. However, delivery systems for controlled release of these drugs have not been investigated. Here we tested the efficacy of several formulations of elastin like recombinamers (ELRs) hydrogels to deliver the Kv1.3 blocker PAP-1 in various restenosis models. The dose and time course of PAP-1 release from ELRs click hydrogels was able to inhibit human VSMC proliferation in vitro as well as remodeling of human vessels in organ culture and restenosis in in vivo models. We conclude that this combination of active compound and advanced delivery method could improve the outcomes of vascular surgery in patients. STATEMENT OF SIGNIFICANCE: Vascular surgery strategies for coronary revascularization show a high rate of failure, because of occlusion (restenosis) of the vessel, due to vascular smooth muscle cells proliferation and migration. We have previously reported that blockers of Kv1.3 channels represent an effective anti-restenosis therapy, but delivery systems for their controlled release have not being explored. Here we tested the efficacy of several formulations of elastin like recombinamers (ELRs) hydrogels to deliver the Kv1.3 blocker PAP-1 in various restenosis models, both in vivo and in vitro, and also in human vessels. We demonstrated that combination of active compound and advanced delivery method could improve the outcomes of vascular surgery in patients.

Myocardin-Dependent Kv1.5 Channel Expression Prevents Phenotypic Modulation of Human Vessels in Organ Culture.

OBJECTIVE: We have previously described that changes in the expression of Kv channels associate to phenotypic modulation (PM), so that Kv1.3/Kv1.5 ratio is a landmark of vascular smooth muscle cells phenotype. Moreover, we demonstrated that the Kv1.3 functional expression is relevant for PM in several types of vascular lesions. Here, we explore the efficacy of Kv1.3 inhibition for the prevention of remodeling in human vessels, and the mechanisms linking the switch in Kv1.3 /Kv1.5 ratio to PM. Approach and Results: Vascular remodeling was explored using organ culture and primary cultures of vascular smooth muscle cells obtained from human vessels. We studied the effects of Kv1.3 inhibition on serum-induced remodeling, as well as the impact of viral vector-mediated overexpression of Kv channels or myocardin knock-down. Kv1.3 blockade prevented remodeling by inhibiting proliferation, migration, and extracellular matrix secretion. PM activated Kv1.3 via downregulation of Kv1.5. Hence, both Kv1.3 blockers and Kv1.5 overexpression inhibited remodeling in a nonadditive fashion. Finally, myocardin knock-down induced vessel remodeling and Kv1.5 downregulation and myocardin overexpression increased Kv1.5, while Kv1.5 overexpression inhibited PM without changing myocardin expression. CONCLUSIONS: We demonstrate that Kv1.5 channel gene is a myocardin-regulated, vascular smooth muscle cells contractile marker. Kv1.5 downregulation upon PM leaves Kv1.3 as the dominant Kv1 channel expressed in dedifferentiated cells. We demonstrated that the inhibition of Kv1.3 channel function with selective blockers or by preventing Kv1.5 downregulation can represent an effective, novel strategy for the prevention of intimal hyperplasia and restenosis of the human vessels used for coronary angioplasty procedures.

Rhamnolipids functionalized with basic amino acids: Synthesis, aggregation behavior, antibacterial activity and biodegradation studies.

Rhamnolipids have been intensively studied due to their remarkable properties; however, the biosynthesis of RLs cannot compete commercially with the production of synthetic surfactants. Here, novel cationic rhamnolipids (RLs) derivatives containing arginine and lysine were prepared for the first time using a straightforward synthetic procedure. The RLs used to prepare these new cationic derivatives were produced by Pseudomonas aeruginosa using waste frying oil as carbon source. It was found that the amino acid-based RLs form aggregates at very low concentrations, even below the CMC. Biodegradation studies indicate that these cationic RLs can be classified as readily biodegradable. Interestingly, the RL arginine conjugates exhibited notable DNA binding affinity and good antimicrobial activity against Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus, which increases the potential applications of these compounds. Consequently, the use of low-cost substrates and the added value of the final product constitute a more cost-effective rhamnolipid production.

Biodegradability and aquatic toxicity of new cleavable betainate cationic oligomeric surfactants.

New cleavable oligomeric cationic surfactants containing ester groups susceptible to hydrolysis between the hydrocarbon tails and the hydrophilic moiety have been synthesized and their biodegradability and aquatic toxicity examined. Aerobic biodegradability was evaluated by applying a standard method for ready biodegradability, the CO2 Headspace test. Aquatic toxicity was assessed by means of the acute toxicity test with Daphnia. Cleavable oligomeric cationic surfactants undergo a significant biodegradation extent (31-52%) as compared to dimeric surfactants without ester groups that showed null degradation in previous works. However, they do not attain the threshold of ultimate degradation required (60%) to be classed as easily biodegradable chemicals. On the other hand, the introduction of cleavable groups in the surfactant hydrophobic chains reduces the toxic effects on the microorganisms responsible for degradation observed for conventional alkyl ammonium dimeric surfactants. Acute toxicity values of betainate cationic oligomeric surfactants to Daphnia magna, IC50-48 h, varies from 1.5 to 50 mg/L. Aquatic toxicity of oligomeric cationic surfactants depends on their hydrophobicity and increases regularly with the alkyl chain length. However, whether the surfactant is a dimeric or a trimeric betaine ester does not affect their acute toxicity to crustacean.

Phenotypic Modulation of Cultured Primary Human Aortic Vascular Smooth Muscle Cells by Uremic Serum.

Patients with chronic kidney disease (CKD) have a markedly increased incidence of cardiovascular disease (CVD). The high concentration of circulating uremic toxins and alterations in mineral metabolism and hormone levels produce vascular wall remodeling and significant vascular damage. Medial calcification is an early vascular event in CKD patients and is associated to apoptosis or necrosis and trans-differentiation of vascular smooth muscle cells (VSMC) to an osteogenic phenotype. VSMC obtained from bovine or rat aorta and cultured in the presence of increased inorganic phosphate (Pi) have been extensively used to study these processes. In this study we used human aortic VSMC primary cultures to compare the effects of increased Pi to treatment with serum obtained from uremic patients. Uremic serum induced calcification, trans-differentiation and phenotypic remodeling even with normal Pi levels. In spite of similar calcification kinetics, there were fundamental differences in osteochondrogenic marker expression and alkaline phosphatase induction between Pi and uremic serum-treated cells. Moreover, high Pi induced a dramatic decrease in cell viability, while uremic serum preserved it. In summary, our data suggests that primary cultures of human VSMC treated with serum from uremic patients provides a more informative model for the study of vascular calcification secondary to CKD.

The secret life of ion channels: Kv1.3 potassium channels and proliferation.

Kv1.3 channels are involved in the switch to proliferation of normally quiescent cells, being implicated in the control of cell cycle in many different cell types and in many different ways. They modulate membrane potential controlling K+ fluxes, sense changes in potential, and interact with many signaling molecules through their intracellular domains. From a mechanistic point of view, we can describe the role of Kv1.3 channels in proliferation with at least three different models. In the "membrane potential model," membrane hyperpolarization resulting from Kv1.3 activation provides the driving force for Ca2+ influx required to activate Ca2+-dependent transcription. This model explains most of the data obtained from several cells from the immune system. In the "voltage sensor model," Kv1.3 channels serve mainly as sensors that transduce electrical signals into biochemical cascades, independently of their effect on membrane potential. Kv1.3-dependent proliferation of vascular smooth muscle cells (VSMCs) could fit this model. Finally, in the "channelosome balance model," the master switch determining proliferation may be related to the control of the Kv1.3 to Kv1.5 ratio, as described in glial cells and also in VSMCs. Since the three mechanisms cannot function independently, these models are obviously not exclusive. Nevertheless, they could be exploited differentially in different cells and tissues. This large functional flexibility of Kv1.3 channels surely gives a new perspective on their functions beyond their elementary role as ion channels, although a conclusive picture of the mechanisms involved in Kv1.3 signaling to proliferation is yet to be reached.

Kv channels and vascular smooth muscle cell proliferation.

Kv channels are present in virtually all VSMCs and strongly influence contractile responses. However, they are also instrumental in the proliferative, migratory, and secretory functions of synthetic, dedifferentiated VSMCs upon PM. In fact, Kv channels not only contribute to all these processes but also are active players in the phenotypic switch itself. This review is focused on the role(s) of Kv channels in VSMC proliferation, which is one of the best characterized functions of dedifferentiated VSMCs. VSMC proliferation is a complex process requiring specific Kv channels at specific time and locations. Their identification is further complicated by their large diversity and the differences in expression across vascular beds. Of interest, both conserved changes in some Kv channels and vascular bed-specific regulation of others seem to coexist and participate in VSMC proliferation through complementary mechanisms. Such a system will add flexibility to the process while providing the required robustness to preserve this fundamental cellular response.

Micellization and Antimicrobial Properties of Surface-Active Ionic Liquids Containing Cleavable Carbonate Linkages.

Imidazolium-based ionic liquids (ILs) containing cleavable carbonate linkages, 1-alkyloxycarbonyloxyethyl-3-methylimidazolium chlorides with alkyl chains of 10, 12, and 14 carbon atoms, were synthesized, and their self-assembly behavior and antimicrobial activity were investigated. Differential scanning calorimetry and polarized optical microscopy studies reveal that carbonate-functionalized ILs form stable thermotropic smectic liquid-crystalline phases over a wide range of temperature. The surface activity and aggregation behavior of these new ILs were investigated by tensiometry, conductometry, potentiometry, and spectrofluorimetry. The size of aggregates was examined by dynamic light scattering (DLS). Carbonate-functionalized ILs display a higher adsorption efficiency and a lower critical micelle concentration (cmc) than simple alkyl-chain-substituted ILs. The insertion of a carbonate ester moiety in the alkyl side chain favors adsorption at the air-water interface and micellization in the bulk solution when compared to nonfunctionalized ILs. DLS measurements show that small micellelike aggregates are spontaneously formed above the cmc. Furthermore, carbonate-functionalized ILs were examined for their antimicrobial activity against a panel of clinically relevant microorganisms. Biological activity was found to increase with hydrophobicity. The presence of a carbonate ester moiety significantly enhances the antimicrobial efficiency as compared to nonfunctionalized ILs, with the susceptibility of Staphylococcus sp. toward the action of these compounds being particularly remarkable. It has been demonstrated that the functionalization of the alkyl side chain of the imidazolium salts can not only modify the aggregation behavior but also lead to differences in both efficiency and the spectrum of antimicrobial activity of amphiphilic ILs.

Lipin-2 regulates NLRP3 inflammasome by affecting P2X7 receptor activation.

Mutations in human LPIN2 produce a disease known as Majeed syndrome, the clinical manifestations of which are ameliorated by strategies that block IL-1ß or its receptor. However the role of lipin-2 during IL-1ß production remains elusive. We show here that lipin-2 controls excessive IL-1ß formation in primary human and mouse macrophages by several mechanisms, including activation of the inflammasome NLRP3. Lipin-2 regulates MAPK activation, which mediates synthesis of pro-IL-1ß during inflammasome priming. Lipin-2 also inhibits the activation and sensitization of the purinergic receptor P2X7 and K+ efflux, apoptosis-associated speck-like protein with a CARD domain oligomerization, and caspase-1 processing, key events during inflammasome activation. Reduced levels of lipin-2 in macrophages lead to a decrease in cellular cholesterol levels. In fact, restoration of cholesterol concentrations in cells lacking lipin-2 decreases ion currents through the P2X7 receptor, and downstream events that drive IL-1ß production. Furthermore, lipin-2-deficient mice exhibit increased sensitivity to high lipopolysaccharide doses. Collectively, our results unveil lipin-2 as a critical player in the negative regulation of NLRP3 inflammasome.

Differences in TRPC3 and TRPC6 channels assembly in mesenteric vascular smooth muscle cells in essential hypertension.

KEY POINTS: Canonical transient receptor potential (TRPC)3 and TRPC6 channels of vascular smooth muscle cells (VSMCs) mediate stretch- or agonist-induced cationic fluxes, contributing to membrane potential and vascular tone. Native TRPC3/C6 channels can form homo- or heterotetrameric complexes, which can hinder individual TRPC channel properties. The possibility that the differences in their association pattern may change their contribution to vascular tone in hypertension is unexplored. Functional characterization of heterologously expressed channels showed that TRPC6-containing complexes exhibited Pyr3/Pyr10-sensitive currents, whereas TRPC3-mediated currents were blocked by anti-TRPC3 antibodies. VSMCs from hypertensive (blood pressure high; BPH) mice have larger cationic basal currents insensitive to Pyr10 and sensitive to anti-TRPC3 antibodies. Consistently, myography studies showed a larger Pyr3/10-induced vasodilatation in BPN (blood pressure normal) mesenteric arteries. We conclude that the increased TRPC3 channel expression in BPH VSMCs leads to changes in TRPC3/C6 heteromultimeric assembly, with a higher TRPC3 channel contribution favouring depolarization of hypertensive VSMCs. ABSTRACT: Increased vascular tone in essential hypertension involves a sustained rise in total peripheral resistance. A model has been proposed in which the combination of membrane depolarization and higher L-type Ca2+ channel activity generates augmented Ca2+ influx into vascular smooth muscle cells (VSMCs), contraction and vasoconstriction. The search for culprit ion channels responsible for membrane depolarization has provided several candidates, including members of the canonical transient receptor potential (TRPC) family. TRPC3 and TRPC6 are diacylglycerol-activated, non-selective cationic channels contributing to stretch- or agonist-induced depolarization. Conflicting information exists regarding changes in TRPC3/TRPC6 functional expression in hypertension. However, although TRPC3-TRPC6 channels can heteromultimerize, the possibility that differences in their association pattern may change their functional contribution to vascular tone is largely unexplored. We probe this hypothesis using a model of essential hypertension (BPH mice; blood pressure high) and its normotensive control (BPN mice; blood pressure normal). First, non-selective cationic currents through homo- and heterotetramers recorded from transfected Chinese hamster ovary cells indicated that TRPC currents were sensitive to the selective antagonist Pyr10 only when TRPC6 was present, whereas intracellular anti-TRPC3 antibody selectively blocked TRPC3-mediated currents. In mesenteric VSMCs, basal and agonist-induced currents were more sensitive to Pyr3 and Pyr10 in BPN cells. Consistently, myography studies showed a larger Pyr3/10-induced vasodilatation in BPN mesenteric arteries. mRNA and protein expression data supported changes in TRPC3 and TRPC6 proportions and assembly, with a higher TRPC3 channel contribution in BPH VSMCs that could favour cell depolarization. These differences in functional and pharmacological properties of TRPC3 and TRPC6 channels, depending on their assembly, could represent novel therapeutical opportunities.

Hexadecyltrimethylammonium bromide (CTA-Br) and 1-butyl-3-methylimidazolium tetrafluoroborate (bmim-BF4) in aqueous solution: An ephemeral binary system.

HYPOTHESIS: Mixtures of the cationic surfactant hexadecyltrimethylammonium bromide (CTA-Br) and the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (bmim-BF4) in aqueous solutions are expected to behave as typical binary cationic surfactant system taking into account the surface activity displayed by the ionic liquid, instead of considering the IL as a water cosolvent. EXPERIMENTS: Surface tension and conductivity measurements have been conducted as a function of the total concentration of the mixtures at different surfactant mole fraction (αCTA-Br) to investigate the surface active properties. FINDINGS: Turbidity immediately appearing when the compounds are mixed in water suggests the spontaneous formation of the low soluble compound hexadecyltrimethylammonium tetrafluoroborate (CTA-BF4), together with the salt formed by the respective counterions bmim+and Br- in solution. For αCTA-Br≠0.5, furthermore of the mentioned compounds, the spare bmim-BF4 (for αCTA-Br<0.5) or CTA-Br (for αCTA-Br>0.5), are also present in the aqueous solution. Systems containing excess of bmim-BF4 show a low critical aggregate concentration (cac), but an unexpected high surface tension at cac (γcac≈53-56mN/m), as pure CTA-BF4. For systems containing excess of CTA-Br, cac increases but γcac decreases up to 36mN/m. Mixtures of pure CTA-BF4 and bmim-BF4 or CTA-Br behave as typical binary surfactant systems.

Hernia de pared abdominal como complicación de la laparoscopia / Abdominal wall hernia as a complication of laparoscopy

El presente artículo nos muestra un caso clínico que ilustra una de las complicaciones de la cirugía laparoscópica, la hernia abdominal. Presentamos el caso de una paciente anticoagulada a la que se le realiza una laparoscópia, el postoperatorio se complica con un cuadro de dolor abdominal y vómitos, y dado que presentaba una masa violácea en la zona de incisión del trocar izquierdo, nos planteamos un diagnóstico diferencial con un hematoma de pared abdominal. El objetivo de este artículo es mostrar la importancia del diagnóstico diferencial de hernia abdominal, en pacientes con múltiples patologías y tratamientos, así como de su diagnóstico temprano. La hernia abdominal es una complicación reparable pero sobre todo prevenible, por lo que es importante revisar las diferentes técnicas quirúrgicas que pueden conseguir una disminución de su incidencia (AU)

This article reports a clinical case that illustrates one of the complications of laparoscopic surgery, abdominal hernia. We present the case of a patient receiving anticoagulant therapy who underwent laparoscopy. The postoperative period was complicated by abdominal pain and vomiting. Because the patient had a purplish mass in the area of the left trocar incision, we carried out a differential diagnosis with an abdominal wall hematoma. The aim of this article is to illustrate the importance of the differential diagnosis of abdominal hernia in patients with multiple diseases and treatments, as well as its early diagnosis. Abdominal hernia is a complication that can be repaired but, most importantly, it can be prevented. It is therefore important to review the different surgical techniques that can decrease their incidence (AU)

Biodegradability and aquatic toxicity of quaternary ammonium-based gemini surfactants: Effect of the spacer on their ecological properties.

Aerobic biodegradability and aquatic toxicity of five types of quaternary ammonium-based gemini surfactants have been examined. The effect of the spacer structure and the head group polarity on the ecological properties of a series of dimeric dodecyl ammonium surfactants has been investigated. Standard tests for ready biodegradability assessment (OECD 310) were conducted for C12 alkyl chain gemini surfactants containing oxygen, nitrogen or a benzene ring in the spacer linkage and/or a hydroxyethyl group attached to the nitrogen atom of the head groups. According to the results obtained, the gemini surfactants examined cannot be considered as readily biodegradable compounds. The negligible biotransformation of the gemini surfactants under the standard biodegradation test conditions was found to be due to their toxic effects on the microbial population responsible for aerobic biodegradation. Aquatic toxicity of gemini surfactants was evaluated against Daphnia magna. The acute toxicity values to Daphnia magna, IC50 at 48 h exposure, ranged from 0.6 to 1 mg/L. On the basis of these values, the gemini surfactants tested should be classified as toxic or very toxic to the aquatic environment. However, the dimeric quaternary ammonium-based surfactants examined result to be less toxic than their corresponding monomeric analogs. Nevertheless the aquatic toxicity of these gemini surfactants can be reduced by increasing the molecule hydrophilicity by adding a heteroatom to the spacer or a hydroxyethyl group to the polar head groups.