Earthquake-enhanced dissolved carbon cycles in ultra-deep ocean sediments

Hadal trenches are unique geological and ecological systems located along subduction zones. Earthquake-triggered turbidites act as efficient transport pathways of organic carbon (OC), yet remineralization and transformation of OC in these systems are not comprehensively understood. Here we measure concentrations and stable- and radiocarbon isotope signatures of dissolved organic and inorganic carbon (DOC, DIC) in the subsurface sediment interstitial water along the Japan Trench axis collected during the IODP Expedition 386. We find accumulation and aging of DOC and DIC in the subsurface sediments, which we interpret as enhanced production of labile dissolved carbon owing to earthquake-triggered turbidites, which supports intensive microbial methanogenesis in the trench sediments. The residual dissolved carbon accumulates in deep subsurface sediments and may continue to fuel the deep biosphere. Tectonic events can therefore enhance carbon accumulation and stimulate carbon transformation in plate convergent trench systems, which may accelerate carbon export into the subduction zones.

P10.12.A CDK12/CDK13 inhibition disrupts a transcriptional program critical for glioblastoma survival

Background

Glioblastoma multiforme (GBM) is the most prevalent and aggressive malignant tumor of the central nervous system. With a median survival of only one year, GBM patients have a particularly poor prognosis, highlighting a clear need for novel therapeutic strategies to target this disease. Transcriptional cyclin-dependent kinases (CDK), which phosphorylate key residues of RNA polymerase II (RNAPII) C-terminal domain (CTD), play a major role in sustaining aberrant transcriptional programs that are key to development and maintenance of cancer cells.

Material and Methods

We used pharmacological inhibition and genetic ablation to study effects of CDK12/CDK13 depletion on the proliferatory and migratory capacity of GBM cells and mouse xenografts. SLAM-seq, CUT&RUN and cell cycle assays were used to study the mechanistic effects of CDK12/CDK13 depletion in GBM cells.

Results

CDK12/CDK13 depletion markedly reduced the proliferatory and migratory capacity of GBM cells, as well as in vivo growth. CDK12/CDK13 inhibition potentiated existing chemotherapeutic treatments. Mechanistically, inhibition of CDK12/CDK13 leads to a genome-wide abrogation of RNAPII CTD phosphorylation, which in turn disrupts transcription and cell cycle progression in GBM cells.

Conclusion

These results provide proof-of-concept for the potential of CDK12 and CDK13 as therapeutic targets for GBM.

Development of the Asia Pacific Consortium on Osteoporosis (APCO) Framework: clinical standards of care for the screening, diagnosis, and management of osteoporosis in the Asia-Pacific region

Guidelines for doctors managing osteoporosis in the Asia-Pacific region vary widely. We compared 18 guidelines for similarities and differences in five key areas. We then used a structured consensus process to develop clinical standards of care for the diagnosis and management of osteoporosis and for improving the quality of care.

PURPOSE

Minimum clinical standards for assessment and management of osteoporosis are needed in the Asia-Pacific (AP) region to inform clinical practice guidelines (CPGs) and to improve osteoporosis care. We present the framework of these clinical standards and describe its development.

METHODS

We conducted a structured comparative analysis of existing CPGs in the AP region using a "5IQ" model (identification, investigation, information, intervention, integration, and quality). One-hundred data elements were extracted from each guideline. We then employed a four-round Delphi consensus process to structure the framework, identify key components of guidance, and develop clinical care standards.

RESULTS

Eighteen guidelines were included. The 5IQ analysis demonstrated marked heterogeneity, notably in guidance on risk factors, the use of biochemical markers, self-care information for patients, indications for osteoporosis treatment, use of fracture risk assessment tools, and protocols for monitoring treatment. There was minimal guidance on long-term management plans or on strategies and systems for clinical quality improvement. Twenty-nine APCO members participated in the Delphi process, resulting in consensus on 16 clinical standards, with levels of attainment defined for those on identification and investigation of fragility fractures, vertebral fracture assessment, and inclusion of quality metrics in guidelines.

CONCLUSION

The 5IQ analysis confirmed previous anecdotal observations of marked heterogeneity of osteoporosis clinical guidelines in the AP region. The Framework provides practical, clear, and feasible recommendations for osteoporosis care and can be adapted for use in other such vastly diverse regions. Implementation of the standards is expected to significantly lessen the global burden of osteoporosis.

Novel use of the Bakri balloon to minimize empty pelvis syndrome following laparoscopic total pelvic exenteration

AIM

Pelvic exenteration is the only surgical option for locally advanced pelvic malignancies infiltrating the surrounding organs. The resultant pelvic void after the procedure is responsible for a number of complications, collectively termed empty pelvis syndrome (EPS). We aim to show how EPS can be minimized by presenting a case series demonstrating the surgical technique of laparoscopic total pelvic exenteration with bilateral pelvic node dissection along with a novel use of the Bakri balloon.

METHOD

This is a case series of three successive patients undergoing laparoscopic total pelvic exenteration for locally advanced primary, nonmetastatic rectal adenocarcinoma over a period of 1 month in a specialized colorectal unit at a tertiary cancer centre. The Bakri balloon was deployed in all three patients and retained for variable time intervals postoperatively. Features of EPS were prospectively documented.

RESULTS

In the first patient, the Bakri balloon was completely deflated and removed on postoperative day (POD) 5. The patient developed subacute intestinal obstruction which resolved with conservative management by POD 12. In the second and third patients, the Bakri balloon was deflated in a sequential manner, beginning on POD 8, until it was finally removed on POD 11. Neither of these patients had any abdominal complaints. A postoperative CT scan of both these patients showed the small bowel loops clearly above the pelvic inlet.

CONCLUSIONS

The Bakri balloon is a simple, safe and cost-effective method to reduce the complications of EPS following laparoscopic total pelvic exenteration. A prospective study is ongoing to objectively quantify the benefits of this technique.

Evidence for the coexistence of spin-glass and ferrimagnetic phases in BaFe12O19 due to basal plane freezing

We present here the results of low-temperature magnetization and X-ray magnetic circular dichroism studies on the single crystals of BaFe12O19 which reveal for the first time the emergence of a spin glass phase, in coexistence with a long-range ordered ferrimagnetic phase, due to the freezing of the basal plane spin component.

Investigation of new magnetoelastic and magnetic transitions accompanied with magnetoelectric coupling in [Formula: see text] multiferroic

A new multiferroic solid solution [Formula: see text] has been developed and characterized for structure, phase transition, magnetoelectric and magnetoelastic coupling. Temperature dependent measurement of dc-magnetization [Formula: see text] on [Formula: see text] ceramic shows two magnetic transitions one around [Formula: see text]42 K and the second at [Formula: see text]130 K. The real part of dielectric permittivity exhibits step like change at the magnetic anomaly temperature ([Formula: see text]130 K) which indicates the presence of magnetoelectric coupling. The change in the value of dielectric permittivity on the application of magnetic field confirms the presence of magnetoelectric coupling in [Formula: see text] ceramic. The room temperature polarization (P)-electric field (E) hysteresis loop measurement shows week ferroelectric nature of sample while the magnetization (M) versus magnetic field (H) measurement suggest weakly ferromagnetic character. The ferroelectric nature of sample was further confirmed by calculating remanent polarization using PUND measurement. The Rietveld structural analysis of low temperature x-ray powder diffraction data does not reveal any crystallographic phase transition in terms of peak splitting or new reflections. However, temperature dependence of lattice parameters, tetragonality, unit cell volume, [Formula: see text] octahedral tilt angle ([Formula: see text]), [Formula: see text] bond length and [Formula: see text] bond angles reveal discontinuous changes at both the magnetic transitions observed in temperature dependence of magnetization. This confirms that both the magnetic anomalies (around [Formula: see text]42 K and [Formula: see text]130 K) exhibit magnetoelastic coupling accompanied with isostructural transitions.

Acute Primary Tuberculous Ulcer of Glans Penis

Acute primary tuberculous ulcer of glans penis is a rare entity even in the endemic region. We present a 55 year old male with multiple undermined ulcers for short duration of 4 weeks with raised erythrocyte sedimentation rate, negative Mantoux test and histopathology revealed a diagnosis of tuberculous ulcer which responded well to antitubercular therapy.

P11.36 Ribosome hydroxylase Mina53 is required for Glioblastoma and is involved in regulation of translation rateand fidelity by regulating ribosomal biogenesis

Glioblastoma multiforme (GBM) is one of the most aggressive types of tumors with a poor response to standard treatment and a median 5-year survival of less than 5%. Therefore, there is an urgent need for new treatments. Recently, a large number of genome-wide studies have shown that the epigenetic modifiers are frequently deregulated in cancer. Using a mouse GBM model, we performed in vitro and in vivo shRNA screens to identify epigenetic regulators required for the tumorigenic process in GBM. Among these regulators is a ribosome hydroxylase Mina53 which hydroxylates His-39 of ribosomal protein, RPL27a. We have found that the knock-down (KD) of Mina53 reduces the in vitro proliferation and colony forming ability of mouse glioma initiating cells (mGIC) and this is dependent on the catalytic activity of Mina. Knock-down of Mina resulted into a small but significant reduction in the global protein synthesis rate. A tandem affinity purification experiment to identify proteins associated with Mina revealed that it is associated mainly with ribosomal proteins, including its substrate RPL27a. Global proteomic analyses revealed that final amounts and de novo protein synthesis of many ribosomal proteins were reduced upon Mina depletion. Isolation and identification of different polysome fraction bound mRNAs using high-throughput sequencing found that mRNAs encoding many ribosomal proteins have lower number of ribosomes loaded on them in the Mina depleted samples compared to the control. Taken together, this study has found that Mina53 is required for glioblastoma and it regulates translation through regulation of ribosomal biogenesis

Efficacy of Isotretinoin and Antihistamine versus Isotretinoin Alone in the Treatment of Moderate to Severe Acne: A Randomised Control Trial

Background Acne vulgaris has considerable impact on physical and psychological health. Isotretinoin is considered most effective drug available for acne therapy but with limited acceptance because of its adverse effects. Antihistamine inhibits inflammatory mediators, Propionibacterium acne induced itching, reduction of squalene and sebum in sebocyte, reduces anxiety and further lessens hormonal derangement and inhibits mast cell induced fibrosis and scars. Clinical relevance is lacking in the use of antihistamine in the treatment of acne and its potential efficacy needs to be clarified. Objective To evaluate the efficacy and safety of combining isotretinoin and antihistamine compare to isotretinoin alone in patients with moderate to severe acne at week 12. Method One hundred patients with moderate to severe acne were included in this randomised, controlled comparative study. Fifty patients were treated with isotretinoin and 50 patients were treated with additional antihistamine, levocetirizine and assessment was done at baseline, 4, 8 and 12 weeks of treatment. Result At week 12, compared to isotretinoin only group, combination of isotretinoin and levocetirizine group showed more statistically significant decrease in score of global acne grading system (51.0 vs. 38.5%) and acne lesion counts (non-inflammatory lesion: 63.2 vs. 44.5%; inflammatory lesions: 75.9 vs. 62.7%; total lesions: 66.07 vs. 48.7%; all p< 0.05). Flaring up of acne occurred less frequently and adverse effects were more tolerable in levocetirizine group. Conclusion Use of antihistamine with isotretinoin provides synergic effect while minimizing the side effect of isotretinoin and greater clearance of the lesion and scars.

Strong Purcell Effect on a Neutral Atom Trapped in an Open Fiber Cavity

We observe a sixfold Purcell broadening of the D_{2} line of an optically trapped ^{87}Rb atom strongly coupled to a fiber cavity. Under external illumination by a near-resonant laser, up to 90% of the atom's fluorescence is emitted into the resonant cavity mode. The sub-Poissonian statistics of the cavity output and the Purcell enhancement of the atomic decay rate are confirmed by the observation of a strongly narrowed antibunching dip in the photon autocorrelation function. The photon leakage through the higher-transmission mirror of the single-sided resonator is the dominant contribution to the field decay (κ≈2π×50  MHz), thus offering a high-bandwidth, fiber-coupled channel for photonic interfaces such as quantum memories and single-photon sources.

Robust Bain distortion in the premartensite phase of a platinum-substituted Ni2MnGa magnetic shape memory alloy

The premartensite phase of shape memory and magnetic shape memory alloys (MSMAs) is believed to be a precursor state of the martensite phase with preserved austenite phase symmetry. The thermodynamic stability of the premartensite phase and its relation to the martensitic phase is still an unresolved issue, even though it is critical to the understanding of the functional properties of MSMAs. We present here unambiguous evidence for macroscopic symmetry breaking leading to robust Bain distortion in the premartensite phase of 10% Pt-substituted Ni2MnGa. We show that the robust Bain-distorted premartensite (T2) phase results from another premartensite (T1) phase with preserved cubic-like symmetry through an isostructural phase transition. The T2 phase finally transforms to the martensite phase with additional Bain distortion on further cooling. Our results demonstrate that the premartensite phase should not be considered as a precursor state with the preserved symmetry of the cubic austenite phase.

Assessment of systemic inflammatory response after total extraperitoneal repair and Lichtenstein repair for inguinal hernia

PURPOSE

The aim of the study was assessment of the systemic inflammatory response (SIR) intensity by measuring the blood serum levels of high sensitivity C-reactive protein (hsCRP), Interleukin-6 (IL-6) and Total Leukocyte Counts of patients. The estimations were done before and after the patient underwent either open Lichtenstein or endoscopic TEP inguinal hernia repair. This is a prospective observational type of study.

METHODS

Sixty patients with a diagnosis of unilateral uncomplicated inguinal hernia were included in the study. Patients were divided into two groups. In the first group, endoscopic total extraperitoneal repair (TEP) was done, while the other group underwent Lichtenstein repair. The patient selection was random. Serum markers for SIR were measured prior to and 24 h post-surgery.

RESULTS

Total extraperitoneal repair (TEP) and open Lichtenstein inguinal hernia repair both cause a significant Systemic Inflammatory Response in the body. The rise in serum markers for SIR post-surgery was statistically significant in both the groups. The rise in serum hsCRP and IL-6 concentrations was observed to be equivocal among the two groups. Statistically significant difference was observed in serum TLC rise: Lichtenstein repair group having a higher value.

CONCLUSION

Both, open and endoscopic surgical techniques incite a systemic inflammatory response in the body. However, it cannot be conclusively stated that TEP is associated with lesser SIR compared to the Lichtenstein repair on the basis of this study.

Studies on bio-chemical profiling of Indian gooseberry (Emblica officinalis) for genetic diversity

Biochemical profiling of physiologically mature fruits of 51 diverse Indian gooseberry (Emblica officinalis Gaertn) germplasm accessions was collected from Vindhyan hill region of Madhya Pradesh, with a view to select nutraceutically rich genotypes based on important biochemical traits. The mean ascorbic acid and total phenol (tannin) content amongst different accessions was recorded as 496.47 mg 100 g⁻¹ and 4.88% with highest value found in CISH A-12 (654.50 mg 100 g⁻¹) and CISH A-30 (7.18%), respectively. Apart from the above, wide range of variability in the composition of other important biochemical attributes viz., total soluble solids (8.60-17.70°Brix), acidity (1.61-2.94%), total sugar (4.15-9.17), reducing sugar (2.19-4.45%) and TSS/acid ratio (3.89-8.33) was also recorded. Highest significant and positive correlation was observed between total sugar and TSS (0.895) followed by reducing sugar and TSS (0.882). Significant positive correlation between ascorbic acid and tannins (0.551) was an indication to be associated with binding capacity of ascorbic acid over a longer period of storage.

Late gestation under- and overnutrition have differential impacts when combined with a post-natal obesogenic diet on glucose-lactate-insulin adaptations during metabolic challenges in adolescent sheep

AIM

To determine whether late gestation under- and overnutrition programme metabolic plasticity in a similar way, and whether metabolic responses to an obesogenic diet in early post-natal life depend on the foetal nutrition history.

METHODS

In a 3 × 2 factorial design, twin-pregnant ewes were for the last 6 weeks of gestation (term = 147 days) assigned to HIGH (N = 13; 150 and 110% of energy and protein requirements, respectively), NORM (N = 9; 100% of requirements) or LOW (N = 14; 50% of requirements) diets. The twin offspring were raised on high-carbohydrate-high-fat (HCHF; N = 35) or conventional (CONV; N = 35) diets from 3 days to 6 months of age (around puberty). Then intravenous glucose (GTT; overnight fasted), insulin (ITT; fed) and propionate (gluconeogenetic precursor; PTT; both fed and fasted) tolerance tests were conducted to evaluate (hepatic) metabolic plasticity.

RESULTS

Prenatal malnutrition differentially impacted adaptations of particularly plasma lactate followed by glucose, cholesterol and insulin. This was most clearly expressed during PTT in fasted lambs and much less during ITT and GTT. In fasted lambs, propionate induced more dramatic increases in lactate than glucose, and HIGH lambs became more hyperglycaemic, hyperlactataemic and secreted less insulin compared to the hypercholesterolaemic LOW lambs. Propionate-induced insulin secretion was virtually abolished in fasted HCHF lambs, but upregulated in fasted compared to fed CONV lambs. HCHF lambs had the greatest glucose-induced insulin secretory responses.

CONCLUSION

Prenatal malnutrition differentially programmed glucose-lactate metabolic pathways and cholesterol homeostasis. Prenatal overnutrition predisposed for hyperglycaemia and hyperlactataemia, whereas undernutrition predisposed for hypercholesterolaemia upon exposure to an obesogenic diet. Prenatal overnutrition (not undernutrition) interfered with pancreatic insulin secretion by non-glucose-dependent mechanisms.

Incommensurate modulations in stoichiometric Ni2MnGa ferromagnetic shape memory alloy: an overview

This article presents a brief overview of our recent work on the nature of long period modulation in the premartensite and martensite phases of Ni2MnGa ferromagnetic shape memory alloy using high resolution synchrotron x-ray powder diffraction patterns. The commensurate structure model using the Pnnm space group is unable to account for the peak positions of the satellite reflections that appear due to modulations correctly. LeBail and Rietveld refinements using the (3+1)-D super space group Immm(00γ)s00 show that the peak positions of all the reflections, including the satellites, can be explained satisfactorily using incommensurate modulations for both the premartensite and martensite phases. The incommensurate modulation vectors are found to be q =0.33761(5) c* =(1/3+δ1) c* and 0.43160(3) c* =(3/7+δ2) c* , where δ1 and δ2 are the degrees of incommensuration for the premartensite and martensite phases, respectively. The periodicity of the closest rational approximant of the premartensite and martensite phases are confirmed to be 3 M and 7 M, respectively, in agreement with single crystal diffraction results.

The World of Perovskites: Phase Transitions and Exotic Properties

Oxide perovskites with a general chemical formula ABO3 constitute an important class of technologically significant materials widely used in commercial capacitors, sensors, actuators and optical devices. The upper part of the earth's lower mantle extending from 670 to 2990 km deep is also predominantly composed of perovskite type (Mg,Fe)SiO3. The perovskite compounds and their solid solutions exhibit many exotic phenomena such as ferroicity, antiferroicity, multiferroicity, piezoelectricity, electrostriction, superconductivity, colossal magnetoresistance, many types of magnetic and cationic orderings and quantum critical point. They owe these phenomena to a rich variety of phase transitions that can be induced by a wide range of variables, such as composition, temperature, pressure, magnetic field, electric field, external stresses and particle size. The main focus of this lecture would be on recent developments on phase transition studies in materials like CaTiO3, SrTiO3, PbTiO3, PbZrO3, NaNbO3, BaTiO3, Pb(Fe1/2Nb1/2)O3, Pb(Mg1/2Nb1/2)O3, BiFeO3and their solid solutions. The examples to be covered in this presentation would include (i) antiferrodistortive tilt transitions (ii) ferroelectric, antiferroelectric, ferrielectric, quantum paraelectric, quantum ferroelectric and relaxor ferroelectric transitions, (iii) morphotropic phase transitions, (iv) isostructural phase transitions, (v) antiferromagnetic and spin reorientation transitions, (vi) tricritical transitions, (vii) stress-induced structural transitions and (vii) size induced transitions. The need for complimentary diffraction techniques (X-ray, neutron and electron diffraction) in conjunction with physical property measurements in capturing the signatures of these phase transitions will be highlighted. The results of group and Landau theory considerations will also be presented. The origin of exotic functional properties of the perovskite compounds and their solid solutions will be discussed.

Expression of recombinant antibody (single chain antibody fragment) in transgenic plant Nicotiana tabacum cv. Xanthi

Plants offer an alternative inexpensive and convenient technology for large scale production of recombinant proteins especially recombinant antibodies (plantibodies). In this paper, we describe the expression of a model single chain antibody fragment (B6scFv) in transgenic tobacco. Four different gene constructs of B6scFv with different target signals for expression in different compartments of a tobacco plant cell with and without endoplasmic reticulum (ER) retention signal were used. Agrobacterium mediated plant transformation of B6scFv gene was performed with tobacco leaf explants and the gene in regenerated plants was detected using histochemical GUS assay and PCR. The expression of B6scFv gene was detected by western blotting and the recombinant protein was purified from putative transgenic tobacco plants using metal affinity chromatography. The expression level of recombinant protein was determined by indirect enzyme-linked immunosorbent assay. The highest accumulation of protein was found up to 3.28 % of the total soluble protein (TSP) in plants expressing B6scFv 1003 targeted to the ER, and subsequently expression of 2.9 % of TSP in plants expressing B6scFv 1004 (with target to apoplast with ER retention signal). In contrast, lower expression of 0.78 and 0.58 % of TSP was found in plants expressing antibody fragment in cytosol and apoplast, without ER retention signal. The described method/system could be used in the future for diverse applications including expression of other recombinant molecules in plants for immunomodulation, obtaining pathogen resistance against plant pathogens, altering metabolic pathways and also for the expression of different antibodies of therapeutic and diagnostic uses.

(3 + 1)D superspace description of the incommensurate modulation in the premartensite phase of Ni2MnGa: a high resolution synchrotron x-ray powder diffraction study

Le Bail and Rietveld analysis of high resolution synchrotron x-ray powder diffraction (SXRPD) data shows unambiguous signatures of the failure of the commensurate 3M modulation model. Using (3 + 1) dimensional superspace group formalism, we have not only confirmed the incommensurate modulation in the premartensite phase with a modulation wavevector of q = 0.337 61(5)c* but also determined the superspace group (Immm(00γ)s00), atomic positions and amplitude of modulations for the incommensurate premartensite phase of Ni2MnGa for the first time. Our results may have important implications in the understanding of the martensitic transition and hence the magnetic field induced strains.

Suspension of the tongue to the digastric tendon following resection of the anterior mandibular arch for oral cancer prevents postoperative tongue fall and avoids the need for tracheostomy

BACKGROUND

Resection of the anterior arch of the mandible leads to tongue fall and postoperative stridor because of the detachment of tongue musculature from the mandible. In this article, a simple method of tongue suspension is described which would prevent such complications and the need for tracheostomy.

SETTINGS AND DESIGN

This study was carried out on patients with oral cancer requiring resection of the anterior arch of the mandible as a part of the surgical resection at a tertiary centre.

MATERIALS AND METHODS

This study was performed on 32 patients with oral cancer requiring resection of the anterior arch of the mandible as a part of the surgical resection. Following an appropriate resection of the oral cancer (including the anterior mandibular arch) and neck dissection, a silk suture is used to loop the tongue musculature on either side to the intermediate tendon of the digastric muscle.

RESULT

This technique of tongue suspension was used in 32 patients who required resection of the anterior mandibular arch for oral cancer. Prophylactic tracheostomy was not performed. One patient developed stridor at extubation and required temporary tracheostomy. All other patients could be successfully extubated within 12 h of surgery and none experienced postoperative stridor or sleep apnea. One other patient required temporary tracheostomy for pulmonary toilet as he developed aspiration pneumonitis related to nasogastric feed.

CONCLUSION

This simple method of tongue suspension to the digastric tendon prevents postoperative tongue fall and obviates the need for tracheostomy in most instances.

Molecular regulation of NADPH oxidase 5 via the MAPK pathway

The mechanisms controlling the activity of NADPH oxidase 5 (Nox5) are unique in that they are independent of the protein: protein interactions that coordinate the activation of other Nox isoforms. Instead, the primary driving force for Nox5 activity is calcium. However, in a previous study we reported that the protein kinase C (PKC)-agonist PMA could induce a sustained activation of Nox5 that was independent of calcium changes. This apparent calcium-independent activation was found to be mediated by the PKC-dependent phosphorylation of specific serine and threonine residues on Nox5 which increased the calcium sensitivity of the enzyme and enabled activation at resting levels of calcium. However, the specific kinase(s) mediating the phosphorylation and activation of Nox5 are not known. As PKC can activate the MEK/ERK1/2 signaling pathway, we hypothesized that Nox5 is activated by the coordinated phosphorylation of both MAPK and PKC pathways. The inhibition of MEK1 using PD-98059 and U-0126 significantly reduced the phosphorylation and activity of Nox5 in response to PMA but not to the calcium-mobilizing stimulus ionomycin. Dominant negative MEK1 and knockdown of endogenous MEK1/2 using a specific small interfering RNA also inhibited Nox5 activity in response to PMA. The mutation of S498 to a nonphosphorylatable residue and to a lesser degree T494 blocked the ability of ERK to stimulate Nox5 activity. However, a constitutively active form of MEK1 failed to increase Nox5 activity in the absence of PMA stimulation. These results suggest that the MEK/ERK1/2 pathway is necessary but not sufficient to regulate the PMA-dependent activation of Nox5.