Promotion of structural plasticity in area V2 of visual cortex prevents against object recognition memory deficits in aging and Alzheimer's disease rodents

JOURNAL/nrgr/04.03/01300535-202408000-00038/figure1/v/2023-12-16T180322Z/r/image-tiff Memory deficit, which is often associated with aging and many psychiatric, neurological, and neurodegenerative diseases, has been a challenging issue for treatment. Up till now, all potential drug candidates have failed to produce satisfactory effects. Therefore, in the search for a solution, we found that a treatment with the gene corresponding to the RGS14414 protein in visual area V2, a brain area connected with brain circuits of the ventral stream and the medial temporal lobe, which is crucial for object recognition memory (ORM), can induce enhancement of ORM. In this study, we demonstrated that the same treatment with RGS14414 in visual area V2, which is relatively unaffected in neurodegenerative diseases such as Alzheimer's disease, produced long-lasting enhancement of ORM in young animals and prevent ORM deficits in rodent models of aging and Alzheimer's disease. Furthermore, we found that the prevention of memory deficits was mediated through the upregulation of neuronal arborization and spine density, as well as an increase in brain-derived neurotrophic factor (BDNF). A knockdown of BDNF gene in RGS14414-treated aging rats and Alzheimer's disease model mice caused complete loss in the upregulation of neuronal structural plasticity and in the prevention of ORM deficits. These findings suggest that BDNF-mediated neuronal structural plasticity in area V2 is crucial in the prevention of memory deficits in RGS14414-treated rodent models of aging and Alzheimer's disease. Therefore, our findings of RGS14414 gene-mediated activation of neuronal circuits in visual area V2 have therapeutic relevance in the treatment of memory deficits.

RGS14414-Mediated Activation of the 14-3-3ζ in Rodent Perirhinal Cortex Induces Dendritic Arborization, an Increase in Spine Number, Long-Lasting Memory Enhancement, and the Prevention of Memory Deficits

The remedy of memory deficits has been inadequate, as all potential candidates studied thus far have shown limited to no effects and a search for an effective strategy is ongoing. Here, we show that an expression of RGS14414 in rat perirhinal cortex (PRh) produced long-lasting object recognition memory (ORM) enhancement and that this effect was mediated through the upregulation of 14-3-3ζ, which caused a boost in BDNF protein levels and increase in pyramidal neuron dendritic arborization and dendritic spine number. A knockdown of the 14-3-3ζ gene in rat or the deletion of the BDNF gene in mice caused complete loss in ORM enhancement and increase in BDNF protein levels and neuronal plasticity, indicating that 14-3-3ζ-BDNF pathway-mediated structural plasticity is an essential step in RGS14414-induced memory enhancement. We further observed that RGS14414 treatment was able to prevent deficits in recognition, spatial, and temporal memory, which are types of memory that are particularly affected in patients with memory dysfunctions, in rodent models of aging and Alzheimer's disease. These results suggest that 14-3-3ζ-BDNF pathway might play an important role in the maintenance of the synaptic structures in PRh that support memory functions and that RGS14414-mediated activation of this pathway could serve as a remedy to treat memory deficits.

RGS14414 treatment induces memory enhancement and rescues episodic memory deficits

Memory deficits affect a large proportion of the human population and are associated with aging and many neurologic, neurodegenerative, and psychiatric diseases. Treatment of this mental disorder has been disappointing because all potential candidates studied thus far have failed to produce consistent effects across various types of memory and have shown limited to no effects on memory deficits. Here, we show that the promotion of neuronal arborization through the expression of the regulator of G-protein signaling 14 of 414 amino acids (RGS14₄₁₄) not only induced robust enhancement of multiple types of memory but was also sufficient for the recovery of recognition, spatial, and temporal memory, which are kinds of episodic memory that are primarily affected in patients or individuals with memory dysfunction. We observed that a surge in neuronal arborization was mediated by up-regulation of brain-derived neurotrophic factor (BDNF) signaling and that the deletion of BDNF abrogated both neuronal arborization activation and memory enhancement. The activation of BDNF-dependent neuronal arborization generated almost 2-fold increases in synapse numbers in dendrites of pyramidal neurons and in neurites of nonpyramidal neurons. This increase in synaptic connections might have evoked reorganization within neuronal circuits and eventually supported an increase in the activity of such circuits. Thus, in addition to showing the potential of RGS14₄₁₄ for rescuing memory deficits, our results suggest that a boost in circuit activity could facilitate memory enhancement and the reversal of memory deficits.-Masmudi-Martín, M., Navarro-Lobato, I., López-Aranda, M. F., Delgado, G., Martín-Montañez, E., Quiros-Ortega, M. E., Carretero-Rey, M., Narváez, L., Garcia-Garrido, M. F., Posadas, S., López-Téllez, J. F., Blanco, E., Jiménez-Recuerda, I., Granados-Durán, P., Paez-Rueda, J., López, J. C., Khan, Z. U. RGS14₄₁₄ treatment induces memory enhancement and rescues episodic memory deficits.

Pharmacological interaction of drugs with immune receptors: the p-i concept

Drug-induced hypersensitivity reactions have been explained by the hapten concept, according to which a small chemical compound is too small to be recognized by the immune system. Only after covalently binding to an endogenous protein the immune system reacts to this so called hapten-carrier complex, as the larger molecule (protein) is modified, and thus immunogenic for B and T cells. Consequently, a B and T cell immune response might develop to the drug with very heterogeneous clinical manifestations. In recent years, however, evidence has become stronger that not all drugs need to bind covalently to the MHC-peptide complex in order to trigger an immune response. Rather, some drugs may bind directly and reversibly to immune receptors like the major histocompatibility complex (MHC) or the T cell receptor (TCR), thereby stimulating the cells similar to a pharmacological activation of other receptors. This concept has been termed pharmacological interaction with immune receptors the (p-i) concept. While the exact mechanism is still a matter of debate, non-covalent drug presentation clearly leads to the activation of drug-specific T cells as documented for various drugs (lidocaine, sulfamethoxazole (SMX), lamotrigine, carbamazepine, p-phenylendiamine, etc.). In some patients with drug hypersensitivity, such a response may occur within hours even upon the first exposure to the drug. Thus, the reaction to the drug may not be due to a classical, primary response, but rather be mediated by stimulating existing, pre-activated, peptide-specific T cells that are cross specific for the drug. In this way, certain drugs may circumvent the checkpoints for immune activation imposed by the classical antigen processing and presentation mechanisms, which may help to explain the peculiar nature of many drug hypersensitivity reactions.

Nonimmediate reactions to systemic corticosteroids suggest an immunological mechanism

BACKGROUND

Administration of corticosteroids (CS) by different routes may cause varying types of allergic reactions, thereby hampering their further use in affected patients. In order to verify an immunological involvement we evaluated a group of patients with symptoms compatible with nonimmediate allergic reactions to CS.

METHODS

Studies included patch and intradermal tests, immunohistochemical studies and controlled administration to reproduce the response. The cytokines interleukin (IL)-4, interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha were quantified in peripheral blood during the response.

RESULTS

Of 32 subjects evaluated presenting nonimmediate urticaria or exanthema, 21 were finally considered positive after re-exposure. The drugs most frequently involved were betamethasone and dexamethasone. Fewer than half the patients responded to prednisolone whilst some responded to three or more CS. Hydrocortisone and deflazacort were well tolerated by all the patients. Subjects with a positive intradermal or patch test had a perivascular mononuclear cell infiltrate with the presence of CD4 and CD8 lymphocytes positive for CD45RO+ (memory) and CD69 (activation marker) cells. Monitoring peripheral blood during the acute response showed expression of IFN-gamma and TNF-alpha, with downregulation of IL-4.

CONCLUSION

Adverse systemic responses to different CS are suggestive of a nonimmediate reaction. The symptoms elicited together with the immunlogical studies suggest a T-cell mediated response. The response to closely related CS was especially marked between betamethasone and dexamethasone, whereas hydrocortisone and deflazacort were well tolerated.

Improvement of toxic epidermal necrolysis after the early administration of a single high dose of intravenous immunoglobulin

BACKGROUND

Toxic epidermal necrolysis (TEN) is a severe disease often induced by drugs. Treatment is controversial, although intravenous immunoglobulins (IVIGs) have been effective.

OBJECTIVE

To report the case of a child with TEN after lamotrigine treatment, who improved 24 hours after IVIG administration.

METHODS

Sequential blood and blister fluid samples were obtained for flow cytometry and reverse transcriptase-polymerase chain reaction analyses.

RESULTS

The first blood sample, taken before IVIG administration, showed normal levels of lymphocyte subsets and CLA (4.0%) but high levels of activated lymphocytes (CD69) (18.0%). After treatment, the CLA+, CD69+, and memory cells increased until day 7, decreasing to normal values at days 15 and 30. In the blister fluid samples, taken on day 1, there were high levels of CD8+ (70.2%; CD4/CD8 ratio, 1:5), CLA+ (18.8%), and CD69+ (70%) cells, decreasing 24 hours after IVIG administration. In the blood samples, there was a Th1 cytokine pattern initially, tending to Th0 with time. Perforin, granzyme B, and Fas ligand were only observed before IVIG administration.

CONCLUSIONS

A single high dose of IVIG interrupted the progression of skin disease and reduced the expression of the apoptotic markers. The immunologic changes, first seen in blister fluid and remaining several days in peripheral blood, indicate that T cells were first recruited to the skin and then recirculated to blood.

Differences in the immunological responses in drug- and virus-induced cutaneous reactions in children

The cutaneous symptoms in non-immediate reactions to drugs are not always clinically distinguishable from those induced by viruses, especially during the early phase of the reaction. Moreover, viral infections and drug reactions often coexist and identification of the etiological agent is necessary. Discerning the differences in the immunological response between both may help in the diagnosis. The aim of this study was to determine possible differences in the immunological response in non-immediate cutaneous reactions to drugs versus cutaneous viral-induced diseases in children. Two groups of children were evaluated: one with non-immediate drug-induced cutaneous reactions (DICR) and another with virus-induced cutaneous reactions (VICR). A third group of children taking the same drugs as the DICR group and with no cutaneous disease or viral infections was included as controls. The lymphocyte markers CD3, CD4, CD8, CD16, CD19, CLA, CD25, CD69, CD45RO, CD45RA were determined by flow cytometry. IL-2, IL-4, IL-5, IFN-gamma, TNF-alpha and IL-10 mRNA were measured by RT-PCR. Data were compared by non-parametric and chi(2) statistical analysis. In DICR group (n=8) the diagnosis was established by temporal association, improvement after drug withdrawal, patch testing, and in some cases by controlled administration. All patients in the VICR group (n=10) were diagnosed based on a positive viral serology: the presence of IgM antibodies or seroconversion of IgG antibodies. There were significant differences between the three groups in peripheral lymphocytes expressing the skin homing receptor CLA (P < 0.01), the early activation marker CD69 (P < 0.001), and the memory (CD3+CD45RO+) (P < 0.02) and naive (CD3+CD45RA+) (P < 0.03) T cell subsets. Children with DICR showed a TH1 mRNA cytokine pattern whereas those with VICR showed a TH0 pattern. In lymphocyte subpopulations from children, differences in the immunological response between DICR and VICR can be detected in the expressions of the activation marker CD69 and the cutaneous homing receptor CLA, and in cytokine mRNA profiles.

Anaphylactic reaction to diphtheria-tetanus vaccine in a child: specific IgE/IgG determinations and cross-reactivity studies

The present study describes the occurrence of an anaphylactic reaction after the administration of the fifth booster dose of DT vaccine in a six-year-old child. Skin test, in vitro determinations of specific IgE antibodies and immunoblotting assays showed that the IgE response was directed against tetanus and diphtheria toxoids (Dtx). IgG antibodies were also detected by ELISA and immunoblotting. The RAST and immunoblotting inhibitions showed no cross-reactivity between the two toxoids, indicating the presence of co-existing but non-cross-reacting IgE and IgG antibodies. This was maintained in two subsequent determinations done 18 and 30 months after the episode. To our knowledge, this is the first study of cross-reactivity between tetanus and diphtheria antigens. We show that simultaneous IgE antibodies to two different toxoids may occur, indicating that after an immediate reaction to DT, a search for IgE antibodies to both tetanus and Dtx should be undertaken.

Expression of the skin-homing receptor in peripheral blood lymphocytes from subjects with nonimmediate cutaneous allergic drug reactions

BACKGROUND

In nonimmediate cutaneous reactions to drugs, the skin is the organ most frequently involved, and T cells may play a relevant role. T cells related to skin immune responses express the cutaneous lymphocyte-associated antigen (CLA), the skin-homing receptor.

METHODS

We studied the expression of the CLA in peripheral blood T cells from nine subjects with exanthematous reactions induced by beta-lactams (4), phenytoin (2), propyphenazone (1), spiramycin plus metronidazol (1), and captopril plus tiazide (1). The cutaneous symptoms appeared at least 6 h after drug intake. CLA expression was evaluated by flow cytometry at the time of the reaction (T1) and 1 month later (T2). HLA-DR activation marker expression was also evaluated at T1. In four patients, it was necessary to readminister the culprit drug to establish a causal relationship, and sequential estimation of the markers was performed. Two control groups were included: healthy controls and subjects exposed to the culprit drugs with good tolerance. Values were compared by nonparametric statistics.

RESULTS

The expression of circulating CLA + T cells at T1 was increased compared to healthy controls (median = 20.4 vs 9.4) (P < 0.001), and the patients also expressed increased levels of HLA-DR (median = 3.8) (P < 0.005). Comparison between T1 and T2 (median = 11.2) also showed differences in levels of CLA+ T cells (P < 0.01). The patients re-exposed to the culprit drug showed an increase followed by a decrease of circulating CLA+ T cells (P < 0.05) and CLA+ HLA-DR+ (P < 0.05) paralleling the symptoms.

CONCLUSIONS

These data support the immunologic nature of delayed skin reactions to drugs, and suggest that these CLA+ T cells parallel the disease evolution and may participate in the pathophysiologic mechanisms.

Anticonvulsant-induced toxic epidermal necrolysis: monitoring the immunologic response

BACKGROUND

Toxic epidermal necrolysis is a severe reaction with skin involvement induced by different drugs and other agents. The mechanisms implicated in the induction of the reaction are poorly understood.

OBJECTIVE

Our purpose was to study the involvement of T lymphocytes and other immunocompetent cells in the peripheral blood, blister fluid, and affected skin of 3 patients who had a severe reaction after receiving anticonvulsant medication.

METHODS

Quantification of T lymphocytes expressing the skin-homing receptor (cutaneous lymphocyte-associated antigen ¿CLA) in peripheral blood, skin, and skin blister fluid and assessment of other adhesion molecules, activation markers, and inflammatory interleukins by flow cytometry, immunohistochemistry, and reverse transcription-PCR.

RESULTS

An increase in CD3(+)CLA(+) cells paralleling the severity of the disease was observed in both peripheral blood and skin, tending to normalize as soon as patient's conditions improved. E-selectin was detected in endothelial vessels in parallel with CLA expression on lymphocytes. An overexpression of TNFalpha, IFN-gamma, and IL-2 was also observed in PBMCs. The expression of the different markers changed over the course of the disease.

CONCLUSIONS

These data show an increase in activated T cells expressing the skin-homing receptor in both tissue and peripheral blood accompanying clinical symptoms, with a recruitment of macrophages and an overexpression of cytokines. All these results suggest an important role for T cells in the production of toxic epidermal necrolysis.

Participation of T lymphocytes in cutaneous allergic reactions to drugs

Immunological mechanisms implicated in drug allergic reactions are not yet well understood, but there is 'in vivo' and 'in vitro' evidence that T lymphocytes are involved in these hypersensitivity reactions. The cutaneous lymphocyte-associated antigen (CLA) is the skin homing receptor and is involved in targeting a skin-selective memory T lymphocyte to cutaneous sites of chronic inflammation. We have seen that CLA expression is increased in circulating T lymphocytes of patients who develop a drug allergic cutaneous reaction, these cells are activated and their CLA values tend to become normal in parallel with the disappearance of skin symptoms, demonstrating that CD3+ CLA+ cells are involved in the immunological mechanisms responsible for the pathogenesis of the chronic inflammation process in cutaneous drug reactions.